Avian Influenza (H5N1) Virus

Fast Facts

  • There is no H5N1 influenza pandemic at this time. Find out more information about the H1N1 influenza pandemic.
  • According to the United Nations Food and Agriculture Organization, eliminating H5N1 in the 6 countries where it is endemic (China, Vietnam, Indonesia, Bangladesh, India, and Egypt) will take over 10 years.
  • According to the WHO, since 2003, the H5N1 virus has killed 343 of the 582 people known to be infected.
  • Most of the human infections can be traced to close contact with infected poultry. There have only been a few cases where human-to-human transmission is thought to have occurred. In those cases, the transmission did not continue beyond the immediate contacts of the primary case. Two recent human fatalities (Jan. 2012) in China did not appear to have had contact with poultry, but investigations and monitoring of contacts of the two deceased persons are ongoing.
  • The H5N1 virus has not been found in the United States as of yet.

What is avian influenza?

Avian influenza, or bird flu, is caused by type A influenza viruses that occur naturally among birds and poultry. There are many different subtypes of type A influenza viruses. Currently, the avian influenza virus of concern worldwide is of the H5N1 subtype and is highly contagious within domestic bird and poultry populations.

Wild birds worldwide carry avian influenza viruses in their intestines, but usually do not get sick from them. However, avian influenza is very contagious among birds and can be deadly for some domesticated birds, including chickens, ducks, and turkeys.

Infected birds shed influenza virus in their saliva, nasal secretions, and feces. As a result, domesticated birds and poultry may become infected through direct contact with infected fecal material or through contact with surfaces (such as dirt or cages) or materials (such as water or feed) that have been contaminated with the virus.

Contact with infected fecal material is the most common of bird-to-bird transmission. Wild ducks often introduce low pathogencicity into domestic flocks raised on range or in open flight pens through fecal contamination. Within a poultry house, transfer of the virus between birds can also occur via airborne secretions. The spread of avian influenza between poultry premises almost always follows the movement of contaminated people and equipment. It can be found on the outer surfaces of egg shells; therefore, transfer of eggs is a potential means of transmission. Airborne transmission of virus from farm to farm is highly unlikely under usual circumstances.

Avian influenza infection in domestic poultry causes two main forms of disease that are distinguished by low and high extremes of virulence. The "low pathogenic" form may go undetected and usually causes only mild symptoms (such as ruffled feathers and a drop in egg production). However, the highly pathogenic form spreads more rapidly through flocks of poultry. This form may cause disease that affects multiple internal organs and has a mortality rate that can reach 90-100% often within 48 hours. The H5N1 virus is highly pathogenic.

How do humans become infected?

The risk from avian influenza is generally low to most people, because the viruses do not usually infect humans. However, H5N1 is one of the few avian influenza viruses to have crossed the species barrier to infect humans. The H1N1 virus is another.

Confirmed cases of human infection from several subtypes of avian influenza infection, including H5N1, have been reported since 1997. H5N1 has caused the largest number of detected cases of severe disease and death in humans. In outbreaks in Asia and Europe, more than half of those infected with the H5N1 virus have died.

To date, most cases of avian influenza infection in humans have resulted from close contact with living, infected poultry (domesticated chicken, ducks, and turkeys) or surfaces contaminated with secretion/excretions from infected birds. Dogs and cats can become infected with virus, so some authorities have expressed concern that they might be able to pass the virus to humans, although there are no documented cases of such transmission to date.

There is concern that the H5N1 virus will adapt over time to be able to infect and spread person-to-person. There was person-to-person transmission of the virus within an Indonesian family in which seven people died. However, such transmission is thought to have occurred in only a very few cases, and did not continue beyond the victim's immediate contacts. In this case, officials insist there was no risk of wider transmission. Scientists found that the virus had mutated slightly, but not into a form that could be passed on easily.

In humans, the symptoms of avian influenza range from typical flu-like symptoms (such as fever, cough, sore throat and muscle aches), to eye infections, pneumonia, acute respiratory distress, diarrhea, brain disease and other severe and life-threatening complications.

Is it safe to eat chicken or eggs? What about duck and game birds?

Chicken and Eggs

The influenza virus is destroyed by heat, so it is safe to eat thoroughly cooked (to 165° degrees F) poultry and eggs. Clean food preparation surfaces with hot, soapy water to eliminate any residue after use. Wash your hands frequently and use waterless alcohol-based hand gels when soap and water is not available.

In December 2008, the USDA released a draft risk assessment that stated that the consumption of HPAIV-contaminated poultry and shell eggs poses a negligible risk to humans if properly cooked. At the same time, data suggests that some people will undercook these products and could become exposed and possibly ill.

The USDA model shows that preventive measures, such as flock testing and increased inspection, would result in increased detection of contaminated flocks and reduce the risk of illnesses by preventing the consumption of contaminated poultry. In addition, effectively recalling shell eggs would substantially reduce the risk to consumers.

To date, there has been no compelling evidence that links eating cooked poultry, eggs, or egg products to avian influenza infections in humans, the draft report said. Though the viruses aren't considered foodborne pathogens, researchers have isolated them from poultry muscle and egg interiors.

Duck and Game Birds

According to the USDA, two human illnesses may have been related to consuming infected duck blood products, though investigators could not rule out contact that the patients may have had with infected poultry.

Hunters are encouraged to follow precautions from the National Wildlife Health Center to protect themselves against wildlife related diseases:

  • Do not handle birds that are obviously sick or found dead.
  • Keep your game birds cool, clean and dry.
  • Do not eat, drink or smoke while handling animals.
  • Use disposable latex gloves when cleaning game. Properly dispose of the gloves.
  • Wash your hands with soap and water or alcohol wipes after dressing birds.
  • Clean all tools and surfaces immediately afterwards. Use hot soapy water, then disinfect with a 10-percent chlorine bleach solution.
  • The standard recommendation for ensuring that any wild game is safely cooked is to make sure the meat reaches 165° degrees F or more during the cooking process.

Will this flu outbreak become a human pandemic?

There is concern that the H5N1 virus will adapt over time to infect and spread person-to-person, potentially causing a pandemic. A pandemic is a global disease outbreak, such as what has been seen with the H1N1 virus. A flu pandemic occurs when a new influenza virus emerges for which people have little or no immunity and for which there is no vaccine. The disease spreads easily, causes serious illness, and can move around the world in very short time.

Because these viruses do not commonly infect humans, there is little or no immune protection against them in the human population. If H5N1 virus were to gain the capacity to spread easily from person to person, a pandemic could begin. However, no one can predict when a pandemic might occur. Experts from around the world are watching the H5N1 situation very closely.

It is important to remember that most cases of avian influenza infection in humans have resulted from close contact with infected poultry (domesticated chicken, ducks, and turkeys) or surfaces contaminated with secretion/excretions from infected birds.

The United States has been working closely with other countries and the World Health Organization (WHO) to strengthen systems to detect outbreaks of influenza that might cause a pandemic.

The Centers for Disease Control and Prevention and the World Health Organization are monitoring and detecting influenza activity around the world for the emergence of possible pandemic strains of influenza virus. The H5N1 virus has not yet appeared in the US. Should it appear in the US, it does not automatically mean there is a pandemic.

Health officials consider the risk to Americans from the current H5N1 avian influenza outbreak to be low, unless they travel to the Asian and European countries most affected. Travelers planning to visit those areas should take appropriate precautions, including avoiding poultry farms and bird markets where live poultry are raised or kept, as well as avoiding any surfaces that appear to be contaminated by poultry feces or secretions.

Preventative measures include washing hands frequently, using waterless alcohol-based hand gels when soap and water is not available, practicing safe food preparation techniques, avoiding undercooked poultry and eggs, and avoiding contact with high-risk birds.

Are there treatments or a vaccine for the H5N1 virus in humans?

Outside of a vaccine, antiviral drugs and supportive care would likely be the first line of treatment for humans. Research to find a vaccine to protect humans against H5N1 virus began in April 2005. The Pandemicflu.gov Web site offers more information about vaccine and treatment progress.

Studies done in laboratories suggest that some of the prescription medicines approved in the United States for human influenza viruses should work in treating avian influenza infection in humans. However, influenza viruses can become resistant to these drugs, so these medications may not always work. Additional studies are needed to demonstrate the effectiveness of these medicines.

There are four approved antiviral drugs for the treatment or prevention of influenza A in humans. These are the adamantanes (amantadine and rimantadine) and the neuraminidase inhibitors (oseltamivir--Tamiflu®--and zanamivir). The drugs are not approved for use in the treatment or prevention of influenza or other viral infections in animals.

Dr. Yoshihiro Kawaoka, University of Wisconsin-Madison School of Veterinary Medicine, reports in a recent study that a new compound proves to be highly effective against the H5N1 virus, even more powerful than the antiviral drug best known by the trade name Tamiflu. The new compound – T-705 – can even protect against illness three days after infection.

The World Health Organization has issued a plan for containing a bird flu outbreak if the virus starts to spread rapidly among humans; the plan includes the rapid mass use of the antiviral Tamiflu®.

Are there treatments or a vaccine for the H5N1 virus in birds and animals?

According to the American Veterinary Medical Association, "Currently, there is no USDA-licensed vaccine against H5N1 highly pathogenic avian influenza infection available for use in companion animals in the United States." Vaccines are being researched.

Of the four antiviral medications approved for use in humans, none are approved for use in animals. The National Wildlife Rehabilitators Association Veterinary Committee strongly recommends that these medications not be used in treating wildlife patients nor prescribed for extra-label use in other animals: "When Tamiflu® is used and then metabolized and excreted by people or other animals, it can persist in the environment for extended periods, potentially leading to avian influenza viruses acquiring drug resistance. Using the medication in wildlife for the prevention of other viral diseases (like parvovirus, distemper, etc.) might well lead to a highly resistant form of avian influenza and other viruses in the environment for which there would be no useful treatments should humans become sick."

In 2005, the World Health Organization (WHO), Food and Agriculture Organization (FAO), and World Organization for Animal Health (OIE) issued a joint statement urging “… not to use antiviral drugs in animals so that the efficacy of these drugs can be preserved for treatment of influenza infections in humans” and strongly requested Member States to ban the use of antiviral drugs in animals. In March 2006, the FDA published a final rule prohibiting the extra-label use of adamantine and neuraminidase inhibitor classes of antiviral drugs in chickens, turkeys, and ducks.

How will we know if the virus has reached the United States?

The Oregon Department of Fish and Wildlife is working with the US Fish and Wildlife Service, the US Department of Agriculture's Wildlife Services, and other agencies to monitor populations of wild migratory birds.

Migratory birds entering Oregon and other Western states from Asia and other continents where the virus is present are expected to first arrive in Alaska and eventually enter Oregon via the Pacific Flyway.

Federal and state officials plan to collect a statistically significant amount of samples from wild birds throughout the Pacific Flyway and test these samples for H5N1. Oregon State University's Veterinary Diagnostic Laboratory will test the samples for genetic signs of avian influenza. If needed, those samples would be sent on to the US Department of Agriculture's main veterinary diagnostic lab in Ames, Iowa, where they would be tested for the H5N1 virus.

The public is asked to report strange bird deaths or mass die-offs to the Department of Fish and Wildlife at (866) 968-2600.

What can I do to protect my poultry, birds and pets? Are other animals susceptible to this virus?

Information about the H1N1 pandemic influenza virus and animals.

Poultry

The biggest threat would be to poultry raised outdoors (for instance, a free-range grower's farm, a backyard farm, or in an outdoor coop in an urban environment) who might be exposed to droppings from migratory birds carrying the virus.

Poultry farms routinely check birds for avian flu. Oregon health officials promise a prompt response if the disease is detected in our state. In the event of an outbreak, a farm would be quarantined and birds suspected of being exposed to the disease would be killed immediately on the farm and their remains composted on-site.

Poultry owners should try to keep birds such as chickens, ducks and turkeys in a screened area and restrict visits from owners of birds with any illness.

The Oregon Department of Agriculture is compiling a list of private poultry flock owners. If bird flu arrives in Oregon, State Veterinarian Dr. Don Hansen says they want to be able to quickly contact those who have have chickens, ducks or other birds. The sign-up is voluntary and it is not for birds that remain inside, such as parakeets or parrots. They plan to use the list only to alert owners when bird flu arrives and what to do. Note: This list is neither for commericial poultry growers nor indoor pet bird owners.

Pet Birds

Keep pet birds indoors and don't allow contact with other birds, especially wild birds.

Outdoor Birds

Experts agree that there is no need to stop watching, feeding or attracting birds to your yard because of avian influenza. Although avian influenza is not currently a threat, people can contract other illnesses from sick birds and their fecal material. Avoid handling sick birds and always wash your hands with soap and water after filling bird feeders.

Here are some tips from the Portland Audubon Society to help reduce the risk of any type of disease transmission via bird feeders and also predation at feeders:

  • Feed only limited amounts of food on a daily basis.
  • Feed only fresh, natural foods.
  • Clean feeders weekly with a 10% bleach solution.
  • Periodically “take a break.” Stop feeding for 5-7 days to allow birds to disperse and reduce habitual predation by natural and introduced predators.
  • If you see signs of disease at your feeder, stop feeding for a 3-4 weeks.
  • Naturescape your yard to provide for the birds in a more natural manner.
  • Remember that bird feeding simply supplements a natural diet. The birds will not starve if you discontinue feeding.

Cats

While cats are not usually susceptible to avian influenza viruses, both wild and domestic cats have become infected with H5N1 and have been shown to be capable of transmitting the virus to other cats. To date, there are no known cases of human infection resulting from exposure to infected cats. For more information, visit the American Veterinary Medical Association's companion animal FAQ.

Dogs

Dogs are not usually susceptible to avian influenza viruses; however, in central Thailand, where the H5N1 strain has been found, dogs have tested positive for its antibodies, suggesting infection in dogs is likely. There is not enough information about the possibility of infection in dogs to know whether there is a risk of transmission between dogs and other animals or to humans. For more information, visit the American Veterinary Medical Association's companion animal FAQ.

Household Pets

The best protection for household pets is to keep them inside whenever possible, keep an eye on what they might be consuming outside, and avoid raw poultry.

Pigs

In Indonesia and China, pigs have been found to have been infected with the H5N1 avian influenza virus. Flu experts worry about H5N1 findings in pigs because the animals can carry human as well as avian influenza viruses, which presents the viruses an opportunity to combine and form new strains.

Published: March 9, 2009;    Updated: January 23, 2012

Filed Under: Zoonotic Diseases

Sources: News reports, CIDRAP, AP, American Veterinary Medical Association, World Health Organization, USDA, PandemicFlu.gov, Oregon Department of Fish and Wildlife, National Wildlife Health Center, National Wildlife Rehabilitation Association, Portland Audubon Society, Oregon State Veterinarian

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