Thursday, July 24, 2008

High-risk exposures for human Influenza A H5N1 infection
In order to understand which people are most likely to be infected by avian influenza, it is important to be aware of the ways that humans have acquired the H5N1 virus. Studies of human cases of H5N1 influenza reveal that certain very specific exposures place individuals at high risk for this disease. Risk factors for human cases of avian influenza were outlined recently by the WHO. 

One aspect of risk depends on whether a person lives in or visits a country where H5N1 has been identified. The other aspect of risk involves having close contact with birds or ill persons from such countries. Specific exposures are summarized below:

For those in countries or territories where Influenza A H5 infections have been a cause of illness in human or animal populations since October, 2003

During the 7-14 days before an onset of symptoms, ≥1 of the following:

1. Contact (within 1 m) with live or dead domestic fowl or wild birds or domestic ducks
2. Exposure to settings where domestic fowl were confined in the previous 6 weeks
3. Unprotected contact* with a person in whom Influenza A H5N1 was confirmed or is being considered
4. Unprotected contact* with a person with an acute unexplained respiratory illness that later resulted in severe pneumonia or death
5. Occupational exposure

• Domestic fowl worker
• Worker in a domestic fowl processing plant
• Domestic fowl culler (catching, bagging, transporting or disposing of birds)
• Worker in a live animal market
• Chef working with live or recently killed domestic fowl
• Dealer or trader in pet birds
• Health care worker
• Worker in laboratory processing samples possibly containing H5N1 virus

* Within touching or speaking distance, 1 m

For those in countries or territories where Influenza A H5 infections have NOT been seen in humans or animals

During the 7-14 days before the onset of symptoms:

1. Close contact with an ill traveler from one of the areas with known Influenza A H5 activity
2. History of travel to a country or territory with reported avian influenza activity due to Influenza A H5N1 in the animal population
3. Living in an area in which there are rumors of the death of domestic fowl AND ≥ 1 of the following:

• Contact within 1 m with live or dead domestic fowl or wild birds in any setting or with domestic ducks
• Exposure to settings in which domestic fowl were confined in the previous 6 weeks
• Contact* with a patient with a confirmed case of Influenza A H5 N1
• Contact *with a person with an unexplained acute respiratory illness that later resulted in severe pneumonia or death
• Occupational exposures, as described above

* Within touching or speaking distance, 1m

Avoid high-risk exposures
At this time, WHO does not recommend restrictions on travel to any areas affected by H5N1 avian influenza, nor does it advise screening travelers returning from such areas. Avoidance of all known risk factors for H5N1 is strongly encouraged and may be the most useful advice for travelers at this time. Planning a travel itinerary with activities that limit the potential risks is especially important when traveling to countries where H5N1 has been identified.

• WHO does not recommend travel restrictions to areas experiencing outbreaks of highly pathogenic avian influenza in birds. This includes those countries which have reported associated cases of human infection
• Although WHO does not recommend the routine screening of travelers coming from affected areas, local health authorities may provide information to travelers regarding risks, risk avoidance, symptoms, and when and where to report should symptoms develop
• In the setting of a widespread epidemic, policies may vary among countries, and could include interventions such as quarantine or border closures in some cases. It is important to maintain current information and communicate with local authorities regarding their own preparedness plans, so that individuals and organizations can anticipate the local response should the level of pandemic phase be heightened

WHO does advise travelers to avoid contact with high-risk environments in affected countries:

• Travelers to areas affected by influenza in birds are not considered to be at high risk of infection unless direct and unprotected exposure to infected birds (including feathers, feces, and undercooked meat and egg products) occurs
• Avoid contact with live animal markets and poultry farms, and any free-ranging or caged poultry. 
• Persons in areas affected by H5N1 should avoid contact with dead migratory birds or with wild birds showing signs of disease.
• Direct contact with infected poultry, or surfaces and objects contaminated by their droppings, is considered the main route of human infection. Large amounts of virus are found in bird droppings. 
• Exposure risk is considered highest during slaughter, defeathering, butchering, and preparation of poultry for cooking. 

For further information about advice for travelers to countries where avian influenza has been reported, click here.

Practice good hand hygiene
Many infectious diseases can be spread by human hands. Soiled hands are an effective means of delivering infectious material (e.g., saliva or other body fluids that may contain viruses) to the nose or eyes, where they can enter the body.

• Handwashing is an important way to reduce exposure to common infectious diseases. Cleaning one’s hands with soap and water removes potentially infectious material from one’s skin.
• Hands should be cleaned before preparing food, eating or touching one’s face, and after handling soiled material (e.g., used tissues, lavatory surfaces), coughing or sneezing, and using the toilet. 
• Waterless alcohol-based hand gels may be used when soap is not available and hands are not visibly soiled. Including alcohol-based gels as part of a travel health kit is strongly encouraged

Employ good food safety practices
There is no evidence to suggest that the avian influenza virus can be transmitted to humans through the handling or consumption of food, notably poultry and eggs. Poultry and eggs should be thoroughly cooked to protect themselves from the possible risks of food poisoning. To limit the risk of infection, not only from avian influenza but from other food borne pathogens such as Salmonella, consumers should ensure that poultry is thoroughly cooked (juice runs clear and no visible pink meat).

• There is no evidence that properly cooked poultry or poultry products can be a source of infection.
• Internal temperatures for whole chicken and parts should reach 82°C-85°C (180ºF), and eggs should be cooked until the yolk is no longer running.
• Wash hands thoroughly with soap and warm water for 15 to 20 seconds after having handled raw poultry and raw eggs. Separate raw poultry and raw eggs from other food products to avoid cross-contamination.
• Any plates, utensils, etc., that have been in contact with raw poultry or raw eggs should be washed in hot soapy water, rinsed and dried or washed in a dishwasher.

Consider pre-travel preparations
A pre-travel health assessment should be considered for any traveler, but especially for individuals with preexisting health conditions. Areas addressed by such a visit will include general advice regarding hygiene and safety and specific information about the location and activities proposed. Suggested vaccinations and appropriate medications can be arranged. Reducing the chance of illness during or after travel to areas affected by avian influenza will limit the need for health evaluation and interventions while away.

While a vaccine against H5N1 for use in humans is not yet available, the vaccine for seasonal influenza is recommended for the following individuals:

• people aged 65 years and older, with and without chronic health conditions
• residents of long-term care facilities
• people aged 2–64 years with chronic health conditions
• children aged 6–23 months
• pregnant women
• health-care personnel who provide direct patient care
• household contacts and out-of-home caregivers of children < 6 months of age

Persons traveling outside the U.S. should consider the vaccine for seasonal influenza. This vaccination does not have a specific effect against the H5N1 strain of Influenza A. Nonetheless, receiving the vaccine may reduce the chances that someone with flu symptoms during travel simply has a harmless respiratory infection that might be confused with bird flu.

• Travelers to areas with avian influenza should consider receiving the trivalent human vaccine, preferably 2 weeks or more prior to departure. 
• Travelers who are candidates should also receive pneumococcal vaccination at least 2 weeks prior to their departure. This includes persons over 65 years, those with chronic cardiac or lung disease, sickle cell anemia, and other chronic diseases. Vaccination will reduce the risk of illness due to bacterial pneumonia in such persons.

For CDC recommendations regarding immunizations in adults and children, please see the CDC webpage of the National Immunization Program.

Take a travel health kit
Check health insurance or obtain a travel health insurance plan prior to travel. Ensure that coverage for medical care and for evacuation are adequate. Take the international contact numbers and other information for the health plan in hand luggage 

Assemble a health kit that contains a thermometer, alcohol-based gel, and other items such as first aid items, mild analgesics and antidiarrheal medicine. Ensure that any prescription medicines or glasses/contacts are carried in hand luggage and that there is an adequate supply.

Monitoring Health
If you believe you might have been exposed to avian influenza, take the following precautions: 

• Monitor your health for 10 days
• If you develop fever, cough, sore throat, or difficulty breathing, diarrhea, or if you develop any illness with fever during this 10-day period, consult a health-care provider
• Before you visit a health-care setting, tell the provider the following:
  1) your symptoms
  2) where you traveled
  3) if you have had direct poultry contact with poultry. 
• The U.S. embassy or consulate can provide names and addresses of local physicians
• Do not travel while ill, unless you are seeking medical care
• Limiting contact with others as much as possible can help prevent the spread of an infectious illness

When antiviral treatment is appropriate
Persons who have had high-risk exposures to H5N1 avian influenza may be potential candidates for use of antivirals, particularly when they have symptoms. Currently available medicines thought to be effective against H5N1 avian influenza include the neuraminidase inhibitors Tamiflu (Oseltamivir) or Relenza (Zanimivir).

• It is very important that medication begin within 48 hours of the onset of symptoms in order to be effective.
• These medications are available only with a doctor’s prescription.
• Because there are no reliable rapid tests available yet to identify Influenza A H5N1 infection in humans, empiric treatment should be started for anyone with symptoms suspicious for avian flu if they have had a high-risk exposure. Confirmatory testing can be done during the course of treatment, and should not delay treatment.
• The optimal dosing and duration of antiviral medicines for avian influenza has not been established yet.

Prophylactic (preventative) use of antiviral medications is appropriate for those individuals at highest risk for acquiring Influenza A H5N1 infection. The high-risk exposures outlined above represent the most important criteria for determining those who might benefit from prophylaxis, particularly close contact with birds or humans confirmed or considered to have H5N1 infection:

• Taking these medications simply due to travel to countries that have been affected by H5 infections is NOT recommended.
• Indiscriminate use of prophylactic Tamiflu is discouraged for several reasons. If a person has no high-risk exposures, it is of limited usefulness. Also, overuse may deplete drug supplies and could promote the development of viral resistance to the drug. 

Indeed, judicious use of antiviral medications is very important, because of the limited supply of antiviral medicines effective against Influenza A H5N1. The policy best supported by current medical evidence is includes:

1. treat known or suspected human cases of avian influenza H5N1, and
2. use antiviral prophylaxis only for those with an exposure and high risk for disease