Swine Flu
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Dr. Bhuiyan, Ma Yousuf MBBS, MSc (Sweden) PGCD (Karolinska Institute)
Swine flu, H1N1 Although the name 'swine flu' brings up a lot of extra fear and worry, it is important to note that swine flu is just an influenza A H1N1 virus. That means that it is just another type of flu virus, just like that causes our typical seasonal flu symptoms. The big difference is that the current swine influenza A (H1N1) virus has components of pig and bird influenza viruses in it, so that humans don't have any immunity to it. That makes it more likely to become a pandemic virus (have the ability to cause a global outbreak) if it can easily spread from person-to-person. So far, even as you see swine flu cases increase, WHO declared endemic. We do know that swine flu symptoms are just like seasonal flu symptoms. Swine Flu Symptoms According to the CDC, like seasonal flu, symptoms of swine flu infections can include: •
fever, which is usually high, but unlike seasonal flu, is sometimes absent
•
cough
•
runny nose or stuffy nose
•
sore throat
•
body aches
•
headache chills
1
•
fatigue or tiredness, which can be extreme
•
diarrhea and vomiting, sometimes, but more commonly seen than with seasonal flu
Signs of a more serious swine flu infection might include pneumonia and respiratory failure.
Serious Swine Flu Symptoms
More serious symptoms that would indicate that a child with swine flu would need urgent medical attention include: •
Fast breathing or trouble breathing
•
Bluish or gray skin color
•
Not drinking enough fluids
•
Severe or persistent vomiting
•
Not waking up or not interacting
•
Being so irritable that the child does not want to be held
•
Flu-like symptoms improve but then return with fever and worse cough
Swine Flu Symptoms vs. a Cold or Sinus Infection
It is important to keep in mind most children with a runny nose or cough will not have swine flu and will not have to see their pediatrician for swine flu testing. This time of year, many other childhood conditions are common, including: •
spring allergies - runny nose, congestion, and cough
•
common cold - runny nose, cough, and low grade fever
•
sinus infections - lingering runny nose, cough, and fever
•
strep throat - sore throat, fever, and a positive strep test
2
What You Need To Know
Swine flu likely spreads by direct contact with respiratory secretions of someone that is sick with swine flu, like if they were coughing and sneezing close to you. People with swine flu are likely contagious for one day before and up to seven days after they began to get sick with swine flu symptoms. Droplets from a cough or sneeze can also contaminate surfaces, such as a doorknob, drinking glass, or kitchen counter, although these germs likely don't survive for more than a few hours. Anti-flu medications, including Tamiflu (oseltamivir) and Relenza (zanamivir), are available to prevent and treat swine flu. The latest swine flu news from the CDC includes advice that students should stay home if they have swine flu symptoms, but schools do not need to close unless they have large clusters of cases that are affecting school functioning. Schools that closed based on previous recommendations, such as if they had a single confirmed case or probable case, can now likely reopen. Interim Recommendations
For clinical care or collection of respiratory specimens from a symptomatic individual (acute respiratory symptoms with or without fever) who is a confirmed case, or a suspected case (ill close contact of a confirmed case) of swine influenza A (H1N1) virus infection: Infectious Period
Persons with swine influenza A (H1N1) virus infection should be considered potentially contagious for up to 7 days following illness onset. Persons who continue to be ill longer than 7 days after illness onset should be considered potentially contagious until symptoms have resolved. Children, especially younger children, might potentially be contagious for longer periods. The duration of infectiousness might vary by swine influenza A (H1N1) virus strain. Non-hospitalized ill persons who are a confirmed or
O
suspected case of swine influenza A (H1N1) virus infection are recommended to stay at home (voluntary isolation) for at least the first 7 days after illness onset except to seek medical care. Case definitions
A confirmed case of swine influenza A (H1N1) virus infection is defined as a person with an acute respiratory illness with laboratory confirmed swine influenza A (H1N1) virus infection at CDC by one or more of the following tests: real-time RT-PCR viral culture four-fold rise in swine influenza A (H1N1) virus-specific neutralizing antibodies A suspected case of swine influenza A (H1N1) virus infection is defined as a person with acute febrile respiratory illness with onset within 7 days of close contact with a person who is a confirmed case of swine influenza A (H1N1) virus infection. Close contact is defined as: within about 6 feet of an ill person who is a confirmed or suspected case of swine influenza A (H1N1) virus infection. Close contact is defined as: within about 6 feet of an ill person who is a confirmed case of swine influenza A virus infection Acute respiratory illness is defined as recent onset of at least two of the following: rhinorrhea or nasal congestion, sore throat, cough (with or without fever or feverishness) Recommendations for health personnel
For healthy individuals (i.e. without a current respiratory illness), including close contacts of cases of confirmed swine influenza virus infection, no personal protective equipment or antiviral chemoprophylaxis is needed, an ill person, suspected or confirmed swine influenza A virus case, the following is recommended: Keep a distance of at least 6 feet from the ill person; or
4
Personal protective equipment: fit-tested N95 respirator [if unavailable, wear a medical (surgical mask)]. For collecting respiratory specimens from an ill confirmed or suspected swine influenza A virus case, the following is recommended: •
Personal
protective equipment: fit-tested disposable
N95 respirator [if
unavailable, wear a medical (surgical mask)], disposable gloves, gown, and goggles. •
When completed, place all PPE in a biohazard bag for appropriate disposal.
•
Wash hands thoroughly with soap and water or alcohol-based hand gel.
Infection Control
Recommended Infection Control for a non-hospitalized patient (ER, clinic or home visit): 1. Separation from others in single room if available until asymptomatic. If the ill person needs to move to another part of the house, they should wear a mask. The ill person should be encouraged to wash hand frequently and follow respiratory hygiene practices. Cups and other utensils used by the ill person should be thoroughly washed with soap and water before use by other persons. Laboratory Studies •
Findings of standard laboratory studies such as a CBC count and electrolytes assessment are nonspecific but helpful in the workup of influenza.
•
Leukopenia and relative lymphopenia are typical findings in influenza.
•
Thrombocytopenia may be present.
•
Viral culture o The criterion standard for diagnosing influenza A and B is a viral culture of nasopharyngeal samples and/or throat samples. o Obtain samples with Dacron swabs and send the samples in appropriate viral transport media (eg, multimicrobe [M4] transport media) to the laboratory to be cultured in several lines of cells. A laboratory diagnosis of
5
influenza is established once specific cytopathic effect is observed or hemadsorption testing findings are positive. Staining the infected cultured cell lines with fluorescent antibody confirms the diagnosis. o The process may require 3-7 days, long after the patient has left the clinic, office, or emergency department and well past the time when drug therapy could be efficacious. •
Direct immunofluorescent tests o
Some laboratories offer direct immunofluorescent tests on fresh specimens, but these tests are labor-intensive and are less sensitive than culture methods. o
These tests require specially trained laboratory
personnel (people generally not available during all shifts, even in large medical centers) for interpretation. •
Serologic studies o In order to overcome the expensive and time-consuming obstacle of culturing, several serologic tests have become available. In reality, many of these are not bedside tests; generally, 30-60 minutes are required to perform the test's multiple steps. o Some rapid tests are performed best in a laboratory, not in the office or emergency department. o Disadvantages to performing these rapid diagnostic tests include the cost of the laboratory personnel, the cost of the test itself, and potential falsenegative results for influenza A and B. Test sensitivities generally range from 60-70%.
•
Office tests o
Recently, the US Food and Drug Administration waived federal Clinical Laboratories Improvement Act (CLIA) requirements and approved 3 office tests for diagnosis. o
Of these, the fastest is the 10-minute QuickVue
bedside test, which yields a sensitivity of 70-80%. o
Because of cost, availability, and sensitivity
issues, most physicians diagnose influenza based on clinical criteria alone.
6
Imaging Studies •
Chest radiography: In elderly or high-risk patients with pulmonary symptoms, perform chest radiography to exclude pneumonia. o
Early radiographic findings include no or minimal bilateral symmetrical interstitial infiltrates.
o
Later, bilateral symmetrical patch infiltrates become visible. o
Focal infiltrates indicate superimposed bacterial pneumonia. Other Tests •
Arterial blood gas o
Severe hypoxemia is present in severe cases of influenza.
o
The A-a gradient may be increased (>35 mm Hg).
Antiviral Treatment Suspected Cases Empiric antiviral treatment is recommended for any ill person suspected to have swine influenza A (H1N1) virus infection. Antiviral treatment with either zanamivir alone or with a combination of oseltamivir and either amantadine or rimantadine should be initiated as soon as possible after the onset of symptoms. Recommended duration of treatment is five days. Recommendations for use of antivirals may change as data on antiviral susceptibilities become available. Antiviral doses and schedules recommended for treatment of swine influenza A (H1N1) virus infection are the same as those recommended for seasonal influenza: Confirmed Cases
For antiviral treatment of a confirmed case of swine influenza A (H1N1) virus infection, either oseltamivir (Tamiflu) or zanamivir (Relenza) may be administered. Recommended duration of treatment is five days. These same antivirals should be considered for
7
treatment of cases that test positive for influenza A but test negative for seasonal influenza viruses H3 and H1 by PCR. Pregnant Women
Oseltamivir, zanamivir, amantadine, and rimantadine are all "Pregnancy Category C" medications, indicating that no clinical studies have been conducted to assess the safety of these medications for pregnant women. Only two cases of amantadine use for severe influenza illness during the third trimester have been reported. However, both amantadine and rimantadine have been demonstrated in animal studies to be teratogenic and embryotoxic when administered at substantially high doses. Because of the unknown effects of influenza antiviral drugs on pregnant women and their fetuses, these four drugs should be used during pregnancy only if the potential benefit justifies the potential risk to the embryo or fetus; the manufacturers' package inserts should be consulted. However, no adverse effects have been reported among women who received oseltamivir or zanamivir during pregnancy or among infants born to such women. Antiviral Chemoprophylaxis For antiviral chemoprophylaxis of swine influenza A (H1N1) virus infection, either oseltamivir or zanamivir are recommended. Duration of antiviral chemoprophylaxis is 7 days after the last known exposure to an ill confirmed case of swine influenza A (H1N1) virus infection. Antiviral dosing and schedules recommended for chemoprophylaxis of swine influenza A (H1N1) virus infection are the same as those recommended for seasonal influenza:
Antiviral chemoprophylaxis (pre-exposure or post-exposure) with either oseltamivir or zanamivir is recommended for the following individuals: 1. Household close contacts who are at high-risk for complications of influenza (persons with certain chronic medical conditions, elderly) of a confirmed or suspected case.
8
2. School children who are at high-risk for complications of influenza (persons with certain chronic medical conditions) who had close contact (face-to-face) with a confirmed or suspected case. 3. Travelers to Mexico who are at high-risk for complications of influenza (persons with certain chronic medical conditions, elderly). 4. Border workers (Mexico) who are at high-risk for complications of influenza (persons with certain chronic medical conditions, elderly). 5. Health care workers or public health workers who had unprotected close contact with an ill confirmed case of swine influenza A (H1N1) virus infection during the case's infectious period. Antiviral chemoprophylaxis (pre-exposure or post-exposure) with either oseltamivir or zanamivir can be considered for the following: Any health care worker who is at high-risk for complications of influenza (persons with certain chronic medical conditions, elderly) who is working in an area with confirmed swine influenza A (H1N1) cases, and who is caring for patients with any acute febrile respiratory illness. Non-high risk persons who are travelers to Mexico, first responders, or border workers who are working in areas with confirmed cases of swine influenza A (H1N1) virus infection. Will a face mask protect me from getting the swine flu, and are there differences in face masks?
Information on the effectiveness of facemasks and respirators for the control of influenza in community settings is extremely limited. Thus, it is difficult to assess their potential effectiveness in controlling swine influenza A (H1N1) virus transmission in these settings. In the absence of clear scientific data, the interim recommendations below have been developed on the basis of public health judgment and the historical use of facemasks and respirators in other settings.
9
In areas with confirmed human cases of swine influenza A (H1N1) virus infection, the risk for infection can be reduced through a combination of actions. No single action will provide complete protection, but an approach combining the following steps can help decrease the likelihood of transmission. These actions include frequent handwashing, covering coughs, and having ill persons stay home, except to seek medical care, and minimize contact with others in the household. Additional measures that can limit transmission of a new influenza strain include voluntary home quarantine of members of households with confirmed or probable swine influenza cases, reduction of unnecessary social contacts, and avoidance whenever possible of crowded settings. When it is absolutely necessary to enter a crowded setting or to have close contact with persons who might be ill, the time spent in that setting should be as short as possible. If used correctly, facemasks and respirators may help reduce the risk of getting influenza, but they should be used along with other preventive measures, such as avoiding close contact and maintaining good hand hygiene. A respirator that fits snugly on your face can filter out small particles that can be inhaled around the edges of a facemask, but compared with a facemask it is harder to breathe through a respirator for long periods of time. When crowded settings or close contact with others cannot be avoided, the use of facemasks or respirators in areas where transmission of swine influenza A (H1N1) virus has been confirmed should be considered as follows: 1. Whenever possible, rather than relying on the use of facemasks or respirators, close contact with people who might be ill and being in crowded settings should be avoided. 2. Facemasks should be considered for use by individuals who enter crowded settings, both to protect their nose and mouth from other people's coughs and to reduce the wearers' likelihood of coughing on others; the time spent in crowded settings should be as short as possible. 3. Respirators should be considered for use by individuals for whom close contact with an infectious person is unavoidable. This can include selected individuals
10
who must care for a sick person (e.g., family member with a respiratory infection) at home. These interim recommendations will be revised as new information about the use of facemasks and respirators in the current setting becomes available. What are the types of face masks and respirators?
Unless otherwise specified, the term "facemasks" refers to disposable masks cleared by the U.S. Food and Drug Administration (FDA) for use as medical devices. This includes facemasks labeled as surgical, dental, medical procedure, isolation, or laser masks. Such facemasks have several designs. One type is affixed to the head with two ties, conforms to the face with the aid of a flexible adjustment for the nose bridge, and may be flat/pleated or duck-billed in shape. Another type of facemask is pre-molded, adheres to the head with a single elastic band, and has a flexible adjustment for the nose bridge. A third type is flat/pleated and affixes to the head with ear loops. Facemasks cleared by the FDA for use as medical devices have been determined to have specific levels of protection from penetration of blood and body fluids. How is swine flu (H1N1) diagnosed simply?
Swine flu is presumptively diagnosed clinically by the patient's history of association with people known to have the disease and their symptoms listed above. Usually, a quick test (for example, nasopharyngeal swab sample) is done to see if the patient is infected with influenza A or B virus. Most of the tests can distinguish between A and B types. The test can be negative (no flu infection) or positive for type A and B. If the test is positive for type B, the flu is not likely to be swine flu (H1N1). If it is positive for type A, the person could have a conventional flu strain or swine flu (H1N1). Swine flu (H1N1) is definitively diagnosed by identifying the particular antigens associated with the virus type. In general, this test is done in a specialized laboratory and is not done by many doctors' offices or hospital laboratories. However, doctors' offices are able to send specimens to specialized laboratories if necessary.
11
What is the prognosis (outlook) for patients that get swine flu (H1N1)?
The following is speculation on the prognosis for swine flu (H1N1) because this disease has only been recently diagnosed and the data is changing daily. This section is based on currently available information. In general, the majority (about 90%-95%) of people that get the disease feel terrible (see symptoms) but recover with no problems, as seen in patients in both Mexico and the U.S. Caution must be taken as the swine flu (H1N1) is still spreading and may become a pandemic. So far, young adults have not done well, and in Mexico, this group currently has the highest mortality rate, but this data could quickly change. The first traceable case in Mexico, termed "patient zero," was a 5-year-old child in Veracruz who has completely recovered. Investigators noted that large pig farms were located close to the boy's home. The first death in the U.S. occurred in a 23-month-old child who was visiting Texas from Mexico but apparently caught the disease in Mexico. People with depressed immune systems historically have worse outcomes than uncompromised individuals; investigators suspect that as swine flu (H1N1) spreads, the mortality rates may rise and be high in this population. Unfortunately, the problem with the prognosis is still unclear. If the mortality is like the conventional flu that causes mortality rates of about 0.1 %, the result would be about 35,000 deaths per year because of the huge number of people that get infected. If the Mexico swine flu (H1N1) ends up with a mortality rate of about 6% and infects the same number of millions of people as conventional flu viruses, the projected numbers could be as high as 2 million deaths in the U.S. alone. This is a bad prognosis for about 2 million people and their families; these potential deaths are major reasons that health officials are so concerned about the spread of this new virus. Another confounding problem with the prognosis of swine flu (H1N1) is that the disease is occurring and spreading in high numbers at the usual end of the flu season. Most flu outbreaks happen between November to the following April, with peak activity between late December to March. This outbreak is not following the usual flu pattern. Some scientists think that swine flu (H1N1) will quickly die out in the summer and may not ever return, while others think it may die down but return with many more cases in the fall,
12
and still others speculate it will become a pandemic that will resemble the outcomes similar to the 1918 influenza pandemic. Some suggest it may resemble the SARS (severe acute respiratory syndrome caused by a coronavirus strain) outbreak in 20022003 in which the disease spread to about 10 countries with over 7,000 cases, over 700 deaths, and a 10% mortality rate. Effective isolation of patients was done in this case, and many investigators think the outbreak was stopped due to this measure. Because swine flu (H1N1) is a new virus and does not seem to be following the usual flu disease pattern, any prognosis is speculative. Reference: 1. Swine influenza World Health Organization 27 April 2009 2. Kimura H, Abiko C, Peng G, et al(April 1997). "Interspecies transmission of influenza C virus between humans and pigs". Virus Res. 48 (1): 71-9. PMID 9140195. http://linkinghub.elsevier.com/retrieve/pii/S0168-1702(96)01427-X. 3. Shin JY, Song MS, Lee EH, Lee YM, Kim SY, Kim HK, Choi JK, Kim CJ, Webby RJ, Choi YK (2006). "Isolation and characterization of novel H3N1 swine influenza viruses from pigs with respiratory diseases in Korea". Journal of Clinical Microbiology44 (11): 3923-7. doi:10.1128/JCM.00904-06. PMID 16928961. 4. World Health Organization (28 October 2005). "H5N1 avian influenza: timeline" (PDF). http://www.who.int/csr/disease/avian_influenza/Timeline_28_10a.pdf. 5. "Swine Flu and You". CDC. 2009-04-26. http://www.cdc.gov/swineflu/swineflu_you.htm. Retrieved on 2009-04-26. 6. Centers for Disease Control and Prevention (April 26, 2009). "CDC Health Update: Swine Influenza A (H1N1) Update: New Interim Recommendations and Guidance for Health Directors about Strategic National Stockpile Materiel".
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Health Alert Network. http://www.cdc.gov/swineflu/HAN/042609.htm. Retrieved on April 27, 2009.
14
Swine flu, H1N1 Although the name 'swine flu' brings up a lot of extra fear and worry, it is important to note that swine flu is just an influenza A H1N1 virus. That means that it is just another type of flu virus, just like that causes our typical seasonal flu symptoms. The big difference is that the current swine influenza A (H1N1) virus has components of pig and bird influenza viruses in it, so that humans don't have any immunity to it. That makes it more likely to become a pandemic virus (have the ability to cause a global outbreak) if it can easily spread from person-to-person. So far, even as you see swine flu cases increase, WHO declared endemic. We do know that swine flu symptoms are just like seasonal flu symptoms. Swine Flu Symptoms According to the CDC, like seasonal flu, symptoms of swine flu infections can include: •
fever, which is usually high, but unlike seasonal flu, is sometimes absent
•
cough
•
runny nose or stuffy nose
•
sore throat
•
body aches
•
headache chills
1
•
fatigue or tiredness, which can be extreme
•
diarrhea and vomiting, sometimes, but more commonly seen than with seasonal flu
Signs of a more serious swine flu infection might include pneumonia and respiratory failure.
Serious Swine Flu Symptoms
More serious symptoms that would indicate that a child with swine flu would need urgent medical attention include: •
Fast breathing or trouble breathing
•
Bluish or gray skin color
•
Not drinking enough fluids
•
Severe or persistent vomiting
•
Not waking up or not interacting
•
Being so irritable that the child does not want to be held
•
Flu-like symptoms improve but then return with fever and worse cough
Swine Flu Symptoms vs. a Cold or Sinus Infection
It is important to keep in mind most children with a runny nose or cough will not have swine flu and will not have to see their pediatrician for swine flu testing. This time of year, many other childhood conditions are common, including: •
spring allergies - runny nose, congestion, and cough
•
common cold - runny nose, cough, and low grade fever
•
sinus infections - lingering runny nose, cough, and fever
•
strep throat - sore throat, fever, and a positive strep test
2
What You Need To Know
Swine flu likely spreads by direct contact with respiratory secretions of someone that is sick with swine flu, like if they were coughing and sneezing close to you. People with swine flu are likely contagious for one day before and up to seven days after they began to get sick with swine flu symptoms. Droplets from a cough or sneeze can also contaminate surfaces, such as a doorknob, drinking glass, or kitchen counter, although these germs likely don't survive for more than a few hours. Anti-flu medications, including Tamiflu (oseltamivir) and Relenza (zanamivir), are available to prevent and treat swine flu. The latest swine flu news from the CDC includes advice that students should stay home if they have swine flu symptoms, but schools do not need to close unless they have large clusters of cases that are affecting school functioning. Schools that closed based on previous recommendations, such as if they had a single confirmed case or probable case, can now likely reopen. Interim Recommendations
For clinical care or collection of respiratory specimens from a symptomatic individual (acute respiratory symptoms with or without fever) who is a confirmed case, or a suspected case (ill close contact of a confirmed case) of swine influenza A (H1N1) virus infection: Infectious Period
Persons with swine influenza A (H1N1) virus infection should be considered potentially contagious for up to 7 days following illness onset. Persons who continue to be ill longer than 7 days after illness onset should be considered potentially contagious until symptoms have resolved. Children, especially younger children, might potentially be contagious for longer periods. The duration of infectiousness might vary by swine influenza A (H1N1) virus strain. Non-hospitalized ill persons who are a confirmed or
O
suspected case of swine influenza A (H1N1) virus infection are recommended to stay at home (voluntary isolation) for at least the first 7 days after illness onset except to seek medical care. Case definitions
A confirmed case of swine influenza A (H1N1) virus infection is defined as a person with an acute respiratory illness with laboratory confirmed swine influenza A (H1N1) virus infection at CDC by one or more of the following tests: real-time RT-PCR viral culture four-fold rise in swine influenza A (H1N1) virus-specific neutralizing antibodies A suspected case of swine influenza A (H1N1) virus infection is defined as a person with acute febrile respiratory illness with onset within 7 days of close contact with a person who is a confirmed case of swine influenza A (H1N1) virus infection. Close contact is defined as: within about 6 feet of an ill person who is a confirmed or suspected case of swine influenza A (H1N1) virus infection. Close contact is defined as: within about 6 feet of an ill person who is a confirmed case of swine influenza A virus infection Acute respiratory illness is defined as recent onset of at least two of the following: rhinorrhea or nasal congestion, sore throat, cough (with or without fever or feverishness) Recommendations for health personnel
For healthy individuals (i.e. without a current respiratory illness), including close contacts of cases of confirmed swine influenza virus infection, no personal protective equipment or antiviral chemoprophylaxis is needed, an ill person, suspected or confirmed swine influenza A virus case, the following is recommended: Keep a distance of at least 6 feet from the ill person; or
4
Personal protective equipment: fit-tested N95 respirator [if unavailable, wear a medical (surgical mask)]. For collecting respiratory specimens from an ill confirmed or suspected swine influenza A virus case, the following is recommended: •
Personal
protective equipment: fit-tested disposable
N95 respirator [if
unavailable, wear a medical (surgical mask)], disposable gloves, gown, and goggles. •
When completed, place all PPE in a biohazard bag for appropriate disposal.
•
Wash hands thoroughly with soap and water or alcohol-based hand gel.
Infection Control
Recommended Infection Control for a non-hospitalized patient (ER, clinic or home visit): 1. Separation from others in single room if available until asymptomatic. If the ill person needs to move to another part of the house, they should wear a mask. The ill person should be encouraged to wash hand frequently and follow respiratory hygiene practices. Cups and other utensils used by the ill person should be thoroughly washed with soap and water before use by other persons. Laboratory Studies •
Findings of standard laboratory studies such as a CBC count and electrolytes assessment are nonspecific but helpful in the workup of influenza.
•
Leukopenia and relative lymphopenia are typical findings in influenza.
•
Thrombocytopenia may be present.
•
Viral culture o The criterion standard for diagnosing influenza A and B is a viral culture of nasopharyngeal samples and/or throat samples. o Obtain samples with Dacron swabs and send the samples in appropriate viral transport media (eg, multimicrobe [M4] transport media) to the laboratory to be cultured in several lines of cells. A laboratory diagnosis of
5
influenza is established once specific cytopathic effect is observed or hemadsorption testing findings are positive. Staining the infected cultured cell lines with fluorescent antibody confirms the diagnosis. o The process may require 3-7 days, long after the patient has left the clinic, office, or emergency department and well past the time when drug therapy could be efficacious. •
Direct immunofluorescent tests o
Some laboratories offer direct immunofluorescent tests on fresh specimens, but these tests are labor-intensive and are less sensitive than culture methods. o
These tests require specially trained laboratory
personnel (people generally not available during all shifts, even in large medical centers) for interpretation. •
Serologic studies o In order to overcome the expensive and time-consuming obstacle of culturing, several serologic tests have become available. In reality, many of these are not bedside tests; generally, 30-60 minutes are required to perform the test's multiple steps. o Some rapid tests are performed best in a laboratory, not in the office or emergency department. o Disadvantages to performing these rapid diagnostic tests include the cost of the laboratory personnel, the cost of the test itself, and potential falsenegative results for influenza A and B. Test sensitivities generally range from 60-70%.
•
Office tests o
Recently, the US Food and Drug Administration waived federal Clinical Laboratories Improvement Act (CLIA) requirements and approved 3 office tests for diagnosis. o
Of these, the fastest is the 10-minute QuickVue
bedside test, which yields a sensitivity of 70-80%. o
Because of cost, availability, and sensitivity
issues, most physicians diagnose influenza based on clinical criteria alone.
6
Imaging Studies •
Chest radiography: In elderly or high-risk patients with pulmonary symptoms, perform chest radiography to exclude pneumonia. o
Early radiographic findings include no or minimal bilateral symmetrical interstitial infiltrates.
o
Later, bilateral symmetrical patch infiltrates become visible. o
Focal infiltrates indicate superimposed bacterial pneumonia. Other Tests •
Arterial blood gas o
Severe hypoxemia is present in severe cases of influenza.
o
The A-a gradient may be increased (>35 mm Hg).
Antiviral Treatment Suspected Cases Empiric antiviral treatment is recommended for any ill person suspected to have swine influenza A (H1N1) virus infection. Antiviral treatment with either zanamivir alone or with a combination of oseltamivir and either amantadine or rimantadine should be initiated as soon as possible after the onset of symptoms. Recommended duration of treatment is five days. Recommendations for use of antivirals may change as data on antiviral susceptibilities become available. Antiviral doses and schedules recommended for treatment of swine influenza A (H1N1) virus infection are the same as those recommended for seasonal influenza: Confirmed Cases
For antiviral treatment of a confirmed case of swine influenza A (H1N1) virus infection, either oseltamivir (Tamiflu) or zanamivir (Relenza) may be administered. Recommended duration of treatment is five days. These same antivirals should be considered for
7
treatment of cases that test positive for influenza A but test negative for seasonal influenza viruses H3 and H1 by PCR. Pregnant Women
Oseltamivir, zanamivir, amantadine, and rimantadine are all "Pregnancy Category C" medications, indicating that no clinical studies have been conducted to assess the safety of these medications for pregnant women. Only two cases of amantadine use for severe influenza illness during the third trimester have been reported. However, both amantadine and rimantadine have been demonstrated in animal studies to be teratogenic and embryotoxic when administered at substantially high doses. Because of the unknown effects of influenza antiviral drugs on pregnant women and their fetuses, these four drugs should be used during pregnancy only if the potential benefit justifies the potential risk to the embryo or fetus; the manufacturers' package inserts should be consulted. However, no adverse effects have been reported among women who received oseltamivir or zanamivir during pregnancy or among infants born to such women. Antiviral Chemoprophylaxis For antiviral chemoprophylaxis of swine influenza A (H1N1) virus infection, either oseltamivir or zanamivir are recommended. Duration of antiviral chemoprophylaxis is 7 days after the last known exposure to an ill confirmed case of swine influenza A (H1N1) virus infection. Antiviral dosing and schedules recommended for chemoprophylaxis of swine influenza A (H1N1) virus infection are the same as those recommended for seasonal influenza:
Antiviral chemoprophylaxis (pre-exposure or post-exposure) with either oseltamivir or zanamivir is recommended for the following individuals: 1. Household close contacts who are at high-risk for complications of influenza (persons with certain chronic medical conditions, elderly) of a confirmed or suspected case.
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2. School children who are at high-risk for complications of influenza (persons with certain chronic medical conditions) who had close contact (face-to-face) with a confirmed or suspected case. 3. Travelers to Mexico who are at high-risk for complications of influenza (persons with certain chronic medical conditions, elderly). 4. Border workers (Mexico) who are at high-risk for complications of influenza (persons with certain chronic medical conditions, elderly). 5. Health care workers or public health workers who had unprotected close contact with an ill confirmed case of swine influenza A (H1N1) virus infection during the case's infectious period. Antiviral chemoprophylaxis (pre-exposure or post-exposure) with either oseltamivir or zanamivir can be considered for the following: Any health care worker who is at high-risk for complications of influenza (persons with certain chronic medical conditions, elderly) who is working in an area with confirmed swine influenza A (H1N1) cases, and who is caring for patients with any acute febrile respiratory illness. Non-high risk persons who are travelers to Mexico, first responders, or border workers who are working in areas with confirmed cases of swine influenza A (H1N1) virus infection. Will a face mask protect me from getting the swine flu, and are there differences in face masks?
Information on the effectiveness of facemasks and respirators for the control of influenza in community settings is extremely limited. Thus, it is difficult to assess their potential effectiveness in controlling swine influenza A (H1N1) virus transmission in these settings. In the absence of clear scientific data, the interim recommendations below have been developed on the basis of public health judgment and the historical use of facemasks and respirators in other settings.
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In areas with confirmed human cases of swine influenza A (H1N1) virus infection, the risk for infection can be reduced through a combination of actions. No single action will provide complete protection, but an approach combining the following steps can help decrease the likelihood of transmission. These actions include frequent handwashing, covering coughs, and having ill persons stay home, except to seek medical care, and minimize contact with others in the household. Additional measures that can limit transmission of a new influenza strain include voluntary home quarantine of members of households with confirmed or probable swine influenza cases, reduction of unnecessary social contacts, and avoidance whenever possible of crowded settings. When it is absolutely necessary to enter a crowded setting or to have close contact with persons who might be ill, the time spent in that setting should be as short as possible. If used correctly, facemasks and respirators may help reduce the risk of getting influenza, but they should be used along with other preventive measures, such as avoiding close contact and maintaining good hand hygiene. A respirator that fits snugly on your face can filter out small particles that can be inhaled around the edges of a facemask, but compared with a facemask it is harder to breathe through a respirator for long periods of time. When crowded settings or close contact with others cannot be avoided, the use of facemasks or respirators in areas where transmission of swine influenza A (H1N1) virus has been confirmed should be considered as follows: 1. Whenever possible, rather than relying on the use of facemasks or respirators, close contact with people who might be ill and being in crowded settings should be avoided. 2. Facemasks should be considered for use by individuals who enter crowded settings, both to protect their nose and mouth from other people's coughs and to reduce the wearers' likelihood of coughing on others; the time spent in crowded settings should be as short as possible. 3. Respirators should be considered for use by individuals for whom close contact with an infectious person is unavoidable. This can include selected individuals
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who must care for a sick person (e.g., family member with a respiratory infection) at home. These interim recommendations will be revised as new information about the use of facemasks and respirators in the current setting becomes available. What are the types of face masks and respirators?
Unless otherwise specified, the term "facemasks" refers to disposable masks cleared by the U.S. Food and Drug Administration (FDA) for use as medical devices. This includes facemasks labeled as surgical, dental, medical procedure, isolation, or laser masks. Such facemasks have several designs. One type is affixed to the head with two ties, conforms to the face with the aid of a flexible adjustment for the nose bridge, and may be flat/pleated or duck-billed in shape. Another type of facemask is pre-molded, adheres to the head with a single elastic band, and has a flexible adjustment for the nose bridge. A third type is flat/pleated and affixes to the head with ear loops. Facemasks cleared by the FDA for use as medical devices have been determined to have specific levels of protection from penetration of blood and body fluids. How is swine flu (H1N1) diagnosed simply?
Swine flu is presumptively diagnosed clinically by the patient's history of association with people known to have the disease and their symptoms listed above. Usually, a quick test (for example, nasopharyngeal swab sample) is done to see if the patient is infected with influenza A or B virus. Most of the tests can distinguish between A and B types. The test can be negative (no flu infection) or positive for type A and B. If the test is positive for type B, the flu is not likely to be swine flu (H1N1). If it is positive for type A, the person could have a conventional flu strain or swine flu (H1N1). Swine flu (H1N1) is definitively diagnosed by identifying the particular antigens associated with the virus type. In general, this test is done in a specialized laboratory and is not done by many doctors' offices or hospital laboratories. However, doctors' offices are able to send specimens to specialized laboratories if necessary.
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What is the prognosis (outlook) for patients that get swine flu (H1N1)?
The following is speculation on the prognosis for swine flu (H1N1) because this disease has only been recently diagnosed and the data is changing daily. This section is based on currently available information. In general, the majority (about 90%-95%) of people that get the disease feel terrible (see symptoms) but recover with no problems, as seen in patients in both Mexico and the U.S. Caution must be taken as the swine flu (H1N1) is still spreading and may become a pandemic. So far, young adults have not done well, and in Mexico, this group currently has the highest mortality rate, but this data could quickly change. The first traceable case in Mexico, termed "patient zero," was a 5-year-old child in Veracruz who has completely recovered. Investigators noted that large pig farms were located close to the boy's home. The first death in the U.S. occurred in a 23-month-old child who was visiting Texas from Mexico but apparently caught the disease in Mexico. People with depressed immune systems historically have worse outcomes than uncompromised individuals; investigators suspect that as swine flu (H1N1) spreads, the mortality rates may rise and be high in this population. Unfortunately, the problem with the prognosis is still unclear. If the mortality is like the conventional flu that causes mortality rates of about 0.1 %, the result would be about 35,000 deaths per year because of the huge number of people that get infected. If the Mexico swine flu (H1N1) ends up with a mortality rate of about 6% and infects the same number of millions of people as conventional flu viruses, the projected numbers could be as high as 2 million deaths in the U.S. alone. This is a bad prognosis for about 2 million people and their families; these potential deaths are major reasons that health officials are so concerned about the spread of this new virus. Another confounding problem with the prognosis of swine flu (H1N1) is that the disease is occurring and spreading in high numbers at the usual end of the flu season. Most flu outbreaks happen between November to the following April, with peak activity between late December to March. This outbreak is not following the usual flu pattern. Some scientists think that swine flu (H1N1) will quickly die out in the summer and may not ever return, while others think it may die down but return with many more cases in the fall,
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and still others speculate it will become a pandemic that will resemble the outcomes similar to the 1918 influenza pandemic. Some suggest it may resemble the SARS (severe acute respiratory syndrome caused by a coronavirus strain) outbreak in 20022003 in which the disease spread to about 10 countries with over 7,000 cases, over 700 deaths, and a 10% mortality rate. Effective isolation of patients was done in this case, and many investigators think the outbreak was stopped due to this measure. Because swine flu (H1N1) is a new virus and does not seem to be following the usual flu disease pattern, any prognosis is speculative. Reference: 1. Swine influenza World Health Organization 27 April 2009 2. Kimura H, Abiko C, Peng G, et al(April 1997). "Interspecies transmission of influenza C virus between humans and pigs". Virus Res. 48 (1): 71-9. PMID 9140195. http://linkinghub.elsevier.com/retrieve/pii/S0168-1702(96)01427-X. 3. Shin JY, Song MS, Lee EH, Lee YM, Kim SY, Kim HK, Choi JK, Kim CJ, Webby RJ, Choi YK (2006). "Isolation and characterization of novel H3N1 swine influenza viruses from pigs with respiratory diseases in Korea". Journal of Clinical Microbiology44 (11): 3923-7. doi:10.1128/JCM.00904-06. PMID 16928961. 4. World Health Organization (28 October 2005). "H5N1 avian influenza: timeline" (PDF). http://www.who.int/csr/disease/avian_influenza/Timeline_28_10a.pdf. 5. "Swine Flu and You". CDC. 2009-04-26. http://www.cdc.gov/swineflu/swineflu_you.htm. Retrieved on 2009-04-26. 6. Centers for Disease Control and Prevention (April 26, 2009). "CDC Health Update: Swine Influenza A (H1N1) Update: New Interim Recommendations and Guidance for Health Directors about Strategic National Stockpile Materiel".
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Health Alert Network. http://www.cdc.gov/swineflu/HAN/042609.htm. Retrieved on April 27, 2009.
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