Outbreak Notice

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Outbreak Notice

Avian Influenza (H5N1)


By: Centers for Disease Control and Prevention

Date: December 29, 2005

Source: Centers for Disease Control and Prevention. "Notice about Avian Influenza A (H5N1) in Asia and Travel during the Lunar New Year."December 29, 2005. Available online at 〈http://www.cdc.gov/travel/other/avian_flu_lunar_newyear_2006_english.htm〉 (accessed February 2, 2006).

About the Author: The Centers for Disease Control and Prevention (CDC) is a federal government agency that provides health and safety information for United States citizens and international health professionals. It reports accurate and timely information regarding health issues, and develops and applies disease prevention and control measures. The CDC is also involved in health promotion and education.


The influenza (flu) virus has always been a major threat to human health. It is highly infectious and, therefore, has the potential to cause epidemics. There are three types of influenza virus, known as A, B, and C. Influenza A is the most worrying to health officials, as it is responsible for most epidemics and pandemics (world-wide epidemics). Indeed, the influenza pandemic of 1918 killed 15-20 million people, more than twice as many as had died in World War I (1915–1918). Influenza A affects both people and animals, such as birds, pigs, horses, seals, and whales. Influenza B affects humans only and causes epidemics within a population, but not pandemics. Influenza C is also confined to humans and usually causes only mild illness.

Influenza A is classified into sub-types depending on the nature of two proteins on the surface of the virus. There are sixteen types of the hemagluttinin (H) surface protein and nine of the neuraminidase (N) protein. This leads to many different H and N combinations, known as subtypes, of influenza A. Subtypes can be further classified into strains, which vary as to how pathogenic, or dangerous, they are.

Avian influenza (bird flu) is common because wild birds are natural hosts for various subtypes of influenza A, including the highly pathogenic H5N1 subtype that is currently causing worldwide concern among public health officials. The virus does not normally make the wild birds sick, but they can transmit it through their saliva and feces. Poultry—domesticated birds like chickens, ducks, and turkeys—can catch influenza from wild birds and, in contrast, the domesticated birds do become sick. Outbreaks of H5N1 bird flu occurred in eight Asian countries—Cambodia, China, Indonesia, Laos, South Korea, Thailand, Japan, and Vietnam—in 2003 and 2004, killing up to 100 percent of some of the flocks affected. Bird flu can spread to humans through contact with infected birds and there have been an increasing number of human cases reported since 1997, with an accompanying mortality rate of more than 50 percent.

CDC is naturally concerned at the prospect of the spread of avian flu to the United States. International travel has always posed a potent risk of spreading disease. If avian flu does enter the country, it will most likely be from someone traveling from a country where they have become infected. Thus, CDC has a duty to warn travelers to take adequate precautions, as detailed in the advice below.


Outbreak Notice

Notice about Avian Influenza A (H5N1) in Asia and Travel during the Lunar New Year

Released: December 29, 2005

Updated: January 18, 2006

This notice in other languages:

  • Chinese (traditional)
  • Vietnamese
  • Thai
  • Indonesian

The Centers for Disease Control and Prevention (CDC) has issued a specific Outbreak Notice for travel during the Lunar New Year to countries reporting human infection with avian influenza A (H5N1) viruses. Because of increased travel to and from countries reporting human infection with H5N1 during the Lunar New Year, and increased preparation and consumption of poultry for the holiday, this notice provides information to travelers about where H5N1 outbreaks are occurring, health measures to take before travel, and what to do if illness occurs during or after travel. CDC issues various levels of notification about disease outbreaks. Currently, CDC and the World Health Organization (WHO) do not recommend restrictions for travel to any of the countries affected by H5N1.

Avian influenza A (H5N1) viruses usually affect wild birds but since 2003 have been associated with serious, widespread disease among poultry, such as chickens, in parts of Asia and Europe. During 2005, outbreaks of H5N1 infection among poultry and other birds have been confirmed in Cambodia, China, Croatia, Indonesia, Kazakhstan, Mongolia, Romania, Russia, Thailand, Turkey, Ukraine, and Vietnam. Poultry outbreaks were also reported in Malaysia and Laos during 2004.

While human infections with H5N1 viruses have been rare, more than 130 human cases have been confirmed by WHO since January 2004. All reported human cases have occurred in Vietnam, Thailand, Cambodia, Indonesia, and China, with more than half of the cases resulting in death. For information about avian influenza and the current number of human cases, please see the World Health Organization (WHO) website at 〈ttp://www.who.int/csr/disease/avian_influenza/en/〉.

Most cases of H5N1 infection in humans have been linked to direct or close contact with infected poultry in the affected countries. Therefore, when possible, individuals should take care to avoid contact with live, well-appearing, sick, or dead poultry and with any surfaces that may have been contaminated by poultry or their feces or secretions. Transmission of H5N1 viruses to two persons through eating uncooked duck blood may also have occurred in Vietnam in 2005. Individuals should never eat uncooked poultry or poultry products, including blood.

CDC collaborates closely with WHO and other partners to closely monitor the H5N1 situation in countries reporting human cases and poultry outbreaks. CDC also works with other U.S. agencies, state and local governments, and private organizations to maintain a high level of surveillance for H5N1 and other potential influenza threats domestically. At this time, neither human cases of avian influenza A (H5N1) nor animal infections have been reported in the United States.

The following are recommendations for travel to areas reporting avian influenza A (H5N1).

Before any international travel to an area affected by H5N1 avian influenza

  • Visit CDC's Travelers' Health website at 〈http://www.cdc.gov/travel〉 to educate yourself and others who may be traveling with you about any disease risks and CDC health recommendations for international travel in areas you plan to visit. For other information about avian influenza, see CDC's avian influenza website: 〈http://www.cdc.gov/flu/avian/index.htm〉.
  • Be sure you are up to date with all your routine vaccinations, and see your doctor or health-care provider, ideally 4-6 weeks before travel, to get any additional vaccinations, medications, or information you may need.
  • Put together a travel health kit containing basic first aid and medical supplies. Be sure to include a thermometer and alcohol-based hand gel to clean your hands. See the Travelers' Health Kit page in Health Information for International Travel for other suggested items.
  • Before your trip, find a doctor or clinic in the country you will be visiting in case you get sick.
  • Check your health insurance plan to see if it covers illness abroad. Consider the purchase of supplemental insurance, as well as trip cancellation insurance or medical evacuation insurance. A list of medical evacuation services is provided on the U.S. Department of State web page Medical Information for Americans Traveling Abroad, at 〈http://travel.state.gov/travel/tips/health/health_1185.html〉.

During travel to an affected area

  • Do not have direct or close contact with poultry, including touching well-appearing, sick, or dead chickens and ducks. Stay away from places such as poultry farms and bird markets where live poultry are raised or kept, and avoid handling surfaces contaminated with poultry feces or secretions.
  • As with other infectious illnesses, one of the most important preventive practices is careful and frequent handwashing. Cleaning your hands often with soap and water removes potentially infectious material from your skin and helps prevent disease transmission. Waterless alcohol-based hand gels may be used when soap is not available and hands are not visibly soiled.
  • Influenza viruses are destroyed by heat; therefore, all foods from poultry, including eggs and poultry blood, should be thoroughly cooked.
  • If you become sick with symptoms such as a fever accompanied by a cough, sore throat, or difficulty breathing or if you develop any illness that requires prompt medical attention, a U.S. consular officer can assist you in locating medical services and informing your family or friends. Inform your health care provider of any possible exposures to avian influenza. See Seeking Health Care Abroad in Health Information for International Travel for more information about what to do if you become sick while abroad. You should not travel until you are free of symptoms, unless your travel is health-related.

When Preparing Food

  • Separate raw meat from cooked or ready-to-eat foods. Do not use the same chopping board or the same knife for preparing raw meat and cooked or ready-to-eat foods.
  • Do not handle either raw or cooked foods without washing your hands in between.
  • Do not place cooked meat back on the same plate or surface it was on before it was cooked.
  • All foods from poultry, including eggs and poultry blood, should be cooked thoroughly. Egg yolks should not be runny or liquid. Because influenza viruses are destroyed by heat, the cooking temperature for poultry meat should reach 70°C (158°F).
  • Wash egg shells in soapy water before handling and cooking, and wash your hands afterwards.
  • Do not use raw or soft-boiled eggs in foods that will not be cooked.
  • After handling raw poultry or eggs, wash your hands and all surfaces and utensils thoroughly with soap and water.

After your return:

  • Monitor your health for 10 days.
  • If you become ill with a fever plus a cough, sore throat, or trouble breathing during this 10-day period, see a doctor. Before you visit a doctors office or clinic, tell them: 1) your symptoms, 2) where you traveled, and 3) if you have had direct contact with poultry or close contact with a very sick person. This way the doctor can be aware that you have traveled to an area reporting avian influenza.
  • Do not travel if you are sick, unless it is for medical care. Limiting contact with others as much as possible can help prevent the spread of infections.


The CDC advice is applicable not only in the context of avian influenza, but to travel health in general. It has much to say, too, about avoiding infection in everyday life. If all travelers heeded simple hygiene rules such as frequent handwashing and taking extra care in food preparation, there would be fewer cases of infection of any kind. When it comes to preventing bird flu the rules for prevention are clear. People catch bird flu by contact with infected poultry. Transmission of the virus from one person to another is rare, although not unknown.

The question now is whether the bird flu virus could undergo genetic changes in humans that would make it more easily transmissible from person to person, possibly resulting in a pandemic. Many public health experts assume that a pandemic is likely in the near future and they believe that urgent action is now needed to stop it from occurring. The first line of defense begins with containing outbreaks in domestic chickens, as well as monitoring the movement of ducks, swans, or other migratory birds that can harbor the virus.

Antigenic shift is a far more abrupt change in the composition of H and N, which creates a new subtype of virus. The immune system would offer no protection against the new virus and so it could spread very rapidly, creating a pandemic. As of early 2006, World Health officials continued to express fear that there will be more cases of H5N1 bird flu in humans and that the virus will undergo antigenic shift to become a more pathogenic and infectious type. Following such a mutation H5N1 will no longer be classified as an avian virus but rather as a human influenza virus.

There are two weapons against a pandemic of bird flu—vaccination and anti-viral drugs. Scientists are working on a vaccine, but the "new" virus needs to have emerged and be identified before this vaccine will be ready. It will also need to be produced on a large scale to protect enough people to stop a pandemic. There are two anti-viral drugs that can treat bird flu—Tamiflu (oseltamivir) and Relenza (zanamivir)—but it is not certain that there will be sufficient doses available in time to protect everyone at risk.

The general public must be made aware of the potential dangers of a pandemic. The popular media too often spread panic and worry about health matters. The CDC, in this travel advice, seeks to educate and inform. Infection is a major public health issue which is not confined to concern about avian influenza. The more we can learn about preventing and fighting infection, the more lives will be saved, both in the United States and around the world.


Web sites

Centers for Disease Control and Prevention. "Information about Avian Influenza (Bird Flu) and Avian Influenza A (H5N1) Virus." 〈http://www.cdc.gov/flu〉 (accessed November 16, 2005).

World Health Organization. "Avian Influenza." 〈http://www.who.int/mediacentre/factsheets/avian_influenza/en/print.html〉 (accessed November 16, 2005).