Health Library: ABCDEFGHIJKLMNOPQRSTUVWXYZ

What You Need to Know About Bird Flu

Q: Are there differences between influenza (the flu) and avian influenza (bird flu)?

A: Yes. Influenza, or the flu, is a contagious illness caused by influenza viruses that attack the respiratory tract--the nose, throat, and lungs. Animals, including birds, as well as humans, can be affected by flu viruses. The flu can cause mild to severe illness and even death. Older people, young children, and people with certain health conditions are most likely to suffer serious complications.

Flu symptoms include fever (usually high), headache, extreme tiredness, dry cough, sore throat, runny or stuffy nose, and muscle aches. Stomach symptoms, such as nausea, vomiting, and diarrhea, also can occur, but they are more common in children than adults. In the most severe, patients can develop life-threatening pneumonia.

Flu statistics

In an average year in the United States:

  • 5 to 20 percent of the population gets the flu

  • More than 200,000 people are hospitalized from flu complications

  • Flu-associated deaths in the U.S. ranged from a low of about 3,000 to a high of about 49,000 people between 1976 and 2006.

The best way for you to protect yourself is to get a flu vaccination each fall.

Avian influenza, or bird flu, is an infection caused by avian flu viruses. These viruses occur naturally among birds. Worldwide, wild birds carry the viruses in their intestines, but they usually do not get sick from them. Avian flu, however, which is spread through saliva, nasal secretions, and feces, is very contagious among birds. It can make some domesticated birds--including chickens, ducks, and turkeys--very sick and kill them.

Effect on birds

Q: How and where has avian flu affected birds?

A: Some avian flu causes only mild symptoms, but the most severe form may spread rapidly through poultry flocks and can kill all or almost all of a flock, often within 48 hours. Influenza A (H5N1), the subtype of most concern now, was first discovered among birds in China in 1986. It wasn't until late 2003, however, that it began spreading quickly through bird populations there and in seven other Asian countries. By March 2004, after more than 100 million birds had either died from the disease or been killed to control the outbreaks, the disease spread was considered under control.

But since 2004, new outbreaks in poultry and other birds have been reported in Asia, Europe, the Near East, and Africa. The Centers for Disease Control and Prevention (CDC) expects the outbreaks may continue, with occasional cases of viral illness spreading people in those areas.

Q: Do avian influenza viruses infect humans?

A: Bird flu viruses usually do not infect humans, but more than 300 confirmed cases of human infection with bird flu viruses have occurred since 1997. The World Health Organization (WHO) maintains situation updates and cumulative reports of human cases of avian influenza A (H5N1). This virus subtype was first detected in humans in Hong Kong in 1997. Six of the known 18 people infected died. Since then, human cases of influenza A (H5N1) infection have been reported in Azerbaijan, Cambodia, China, Djibouti, Egypt, Indonesia, Iraq, Lao People's Democratic Republic, Nigeria, Thailand, Turkey, and Vietnam.

Human infection

Q: How do people become infected with avian influenza viruses?

A: Most cases of avian influenza infection in humans have resulted from direct or close contact with infected poultry or surfaces contaminated with secretions and excretions from infected birds. In very rare cases, avian flu viruses have spread from one ill person to another person, and transmission has not continued beyond that second person.

Q: What precautions can I take to protect myself and my family?

A: To limit the spread of germs and prevent infection, the CDC offers these recommendations:

  • Wash hands frequently with soap and water.

  • Cover coughs and sneezes with tissues.

  • Stay away from others as much as possible if they are sick.

  • Stay home from work and school if you are sick.

  • Don't shake hands with anyone who appears to be sick.

Vaccine

Q: Is there a vaccine to protect humans from H5N1 virus?

A: Yes. In April 2007, the FDA announced its approval of the first vaccine to prevent human infection with one strain of the avian influenza (bird flu) H5N1 virus. The vaccine has been purchased by the federal government for the U.S. Strategic National Stockpile; it will be distributed by public health officials if needed. This vaccine will not be made commercially available to the general public. Other H5N1 vaccines are being developed by other companies against different H5N1 strains.

Q: How is infection with H5N1 virus in humans treated?

A: Two of the four antiviral medications commonly used for treatment of patients with influenza--oseltamivir (Tamiflu) and zanamivir--would probably treat influenza caused by H5N1 virus. Additional studies are needed to demonstrate their current and ongoing effectiveness.

Because both vaccine and anti-viral medications may be in short supply in the event of a pandemic (a worldwide outbreak of the disease), the government and local health departments will have an important role in determining how they are distributed.

Q: Is there a risk of becoming infected with avian influenza by eating poultry?

A: The U.S. government carefully controls domestic and imported food products. In 2004, the United States issued a ban on importing poultry from countries affected by avian influenza viruses, including the H5N1 strain. This ban was later rescinded, but the CDC states they will continue t work closely with the U.S. Department of Agriculture (USDA), the World Health Organization, the World Animal Health Organization, the Food and Agriculture Organization, and individual Ministries of Health to monitor the situation regarding the H5N1 virus in foreign countries to ensure that the threat to human health is being adequately addressed through animal control measures. For more information, see the CDC Web page on the embargo of birds, http://www.cdc.gov/flu/avian/outbreaks/embargo.htm. There is no evidence, however, that poultry or eggs properly cooked (at or above 160 degrees F) can be a source of infection for avian influenza viruses. For more information about avian influenza and food safety issues, visit the WHO at this website: http://who.int/foodsafety/micro/avian/en/.

Travel precautions

Q: Should I avoid traveling to areas with known H5N1 outbreaks?

A: The CDC currently does not recommend any travel restrictions to affected countries. It does advise travelers to countries with known outbreaks of H5N1 influenza to avoid poultry farms, contact with animals in live food markets, and any surfaces that appear to be contaminated with feces from poultry or other animals.

Q: Where can I go for the latest information about avian flu?

A: The CDC and the WHO are two reliable sources for bird flu information:

  • CDC: http://www.cdc.gov/flu/avian/index.htm

  • WHO: http://www.who.int/csr/disease/avian_influenza/updates/en/index.html

Q: What are the symptoms of avian influenza in humans?

A: Symptoms of avian influenza in humans have ranged from typical human influenza-like symptoms (fever, cough, sore throat, and muscle aches) to eye infections, pneumonia, severe respiratory diseases (such as acute respiratory distress syndrome), and other severe and life-threatening complications. The symptoms of avian influenza may depend on which specific virus subtype and strain caused the infection.

Aggressive infection

Q: How deadly is the virus?

A: Most laboratory-confirmed cases have occurred in previously healthy children and young adults. They appear to have been infected primarily by close contact with birds and poultry. Unlike seasonal influenza, in which infection usually causes only mild respiratory symptoms in most people, H5N1 infection may be very aggressive, with rapid deterioration and high fatality. Primary viral pneumonia and multiple organ failure have been common.

It is possible, however, that the only cases currently being reported are those involving the most severely ill people. Perhaps the disease might not be as deadly as it appears because some infected people not included in the disease counts might not have been affected as severely.

Q: What are the risks to humans from the current H5N1 outbreak in Asia and Europe?

A: Because all influenza viruses have the ability to change, scientists are concerned that H5N1 virus one day could start to spread easily from one person to another. Because these viruses do not commonly infect humans, there is little or no immune protection against them in the human population.

If the H5N1 virus were able to spread easily from person to person, an influenza pandemic could begin.

Pandemic history

Q: Have flu pandemics occurred before?

A: Yes. In 1918, the "Spanish flu" swept around the world and killed at least 40 million people, the worst death toll from any single cause in history. It was caused by a virulent strain of the flu virus that infected both birds and humans.

Despite the development of flu vaccine in the mid 1940s, influenza pandemics caused an estimated 2 million deaths in 1957-58 (Asian flu) and killed an estimated million people in 1968-69 (Hong Kong flu).

Q: How quickly can pandemics spread around the world?

A: The previous pandemics spread around the world in six to nine months in a time when most international travel was by ship. Given the speed and volume of international air travel today, the virus could possibly reach all continents much more quickly.

Q: What's the future outlook?

A: No one can say for sure. The future of bird flu is unpredictable. Flu experts believe a pandemic can possibly be prevented or minimized, or might not materialize. In 1976, for example, the CDC predicted a swine flu epidemic. A new vaccine was rapidly made available, but the pandemic never appeared.