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Avian Influenza (Bird Flu)

Assessment of Current Situation

(updated June 30, 2006)

Avian influenza in birds

Avian influenza is an infection caused by avian (bird) influenza (flu) viruses. These influenza viruses occur naturally among birds. Wild birds worldwide carry the viruses in their intestines, but usually do not get sick from them. However, avian influenza is very contagious among birds and can make some domesticated birds, including chickens, ducks, and turkeys, very sick and kill them.
Infected birds shed influenza virus in their saliva, nasal secretions, and feces. Susceptible birds become infected when they have contact with contaminated secretions or excretions or with surfaces that are contaminated with secretions or excretions from infected birds. Domesticated birds may become infected with avian influenza virus through direct contact with infected waterfowl or other infected poultry, or through contact with surfaces (such as dirt or cages) or materials (such as water or feed) that have been contaminated with the virus.
Infection with avian influenza viruses 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.

Human infection with avian influenza viruses

There are many different subtypes of type A influenza viruses. These subtypes differ because of changes in certain proteins on the surface of the influenza A virus (hemagglutinin [HA] and neuraminidase [NA] proteins). There are 16 known HA subtypes and 9 known NA subtypes of influenza A viruses. Many different combinations of HA and NA proteins are possible. Each combination represents a different subtype. All known subtypes of influenza A viruses can be found in birds.
Usually, “avian influenza virus” refers to influenza A viruses found chiefly in birds, but infections with these viruses can occur in humans. The risk from avian influenza is generally low to most people, because the viruses do not usually infect humans. However, confirmed cases of human infection from several subtypes of avian influenza infection have been reported since 1997. Most cases of avian influenza infection in humans have resulted from contact with infected poultry (e.g., domesticated chicken, ducks, and turkeys) or surfaces contaminated with secretion/excretions from infected birds. The spread of avian influenza viruses from one ill person to another has been reported very rarely, and transmission has not been observed to continue beyond one person.
“Human influenza virus” usually refers to those subtypes that spread widely among humans. There are only three known A subtypes of influenza viruses (H1N1, H1N2, and H3N2) currently circulating among humans. It is likely that some genetic parts of current human influenza A viruses came from birds originally. Influenza A viruses are constantly changing, and they might adapt over time to infect and spread among humans.
During an outbreak of avian influenza among poultry, there is a possible risk to people who have contact with infected birds or surfaces that have been contaminated with secretions or excretions from infected birds.
Symptoms of avian influenza in humans have ranged from typical human influenza-like symptoms (e.g., fever, cough, sore throat, and muscle aches) to eye infections, pneumonia, severe respiratory diseases (such as acute respiratory distress), and other severe and life-threatening complications. The symptoms of avian influenza may depend on which virus caused the infection.
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.

Treatment and vaccination for H5N1 virus in humans

The H5N1 virus that has caused human illness and death in Asia is resistant to amantadine and rimantadine, two antiviral medications commonly used for influenza. Two other antiviral medications, oseltamavir and zanamavir, would probably work to treat influenza caused by H5N1 virus, but additional studies still need to be done to demonstrate their effectiveness.
There currently is no commercially available vaccine to protect humans against H5N1 virus that is being seen in Asia and Europe. However, vaccine development efforts are taking place. Research studies to test a vaccine to protect humans against H5N1 virus began in April 2005, and a series of clinical trials is under way.

Human H5N1 Cases

Human Cases: Summary of Current Situation
Since January, 2004 the World Health Organization has reported human cases of avian influenza A (H5N1) in the following countires:
East Asia and the Pacific:
Cambodia
China
Indonesia
Thailand
Vietnam
Europe & Eurasia:
Azerbaijan
Turkey
Near East:
Egypt
Iraq

KEY FACTS

Key Facts about Avian Influenza (Bird Flu) and Avian Influenza A (H5N1) Virus

What is avian influenza (bird flu)?

Bird flu is an infection caused by avian (bird) influenza (flu) viruses. These flu viruses occur naturally among birds. Wild birds worldwide carry the viruses in their intestines, but usually do not get sick from them. However, bird flu is very contagious among birds and can make some domesticated birds, very sick and kill them, including chickens, ducks, and turkeys. Avian influenza viruses are highly species – specific, but have, on rare occasions, crossed the species barrier to infect humans

In domestic poultry, infection with avian influenza viruses causes two main forms of disease, distinguished by low and high extremes of virulence. The so-called “low pathogenic” form commonly causes only mild symptoms (ruffled feathers, a drop in egg production) and may easily go undetected. The “highly pathogenic” form is far more dramatic. It spreads very rapidly through poultry flocks, causes diseases affecting multiple internal organs, and has a mortality that can approach 100%, often within 48 hours.

What is the avian influenza A (H5N1) virus that has been reported in Africa, Asia, Europe, and near East?

Influenza A (H5N1) virus – also called “H5N1 virus” – is an influenza A virus subtype that occurs mainly in birds, it is highly contagious among birds, and can be deadly to them.
Outbreaks of avian influenza H5N1 occurred among poultry in eight countries in Asia (Cambodia, China, Indonesia, Japan, Laos, South Korea, Thailand, and Vietnam) during late 2003 and early 2004. At that time, more than 100 million birds in the affected countries either died from the disease or were killed in order to try to control the outbreaks.
Since late June 2004, however, new outbreaks of influenza H5N1 among poultry and wild birds have been reported in countries in Africa, Asia, Europe and the Near East.

How do people become infected?

Direct contact with infected poultry, or surfaces and objects contaminated by their feces, is presently considered the main route of human infection. To date, most human cases have occurred in rural or periurban areas where many households keep small poultry flocks, which often roam freely, sometimes entering homes or sharing outdoor areas where children play. As infected birds shed large quantities of virus in their feces, opportunities for exposure to infected droppings or to environments contaminated by the virus are abundant under such conditions. Moreover, because many households in Asia depend on poultry for income and food, many families sell or slaughter and consume birds when signs of illness appear in a flock, and this practice has proved difficult to change. Exposure is considered most likely during slaughtering, defeathering, butchering, and in preparation of poultry for cooking. There is no evidence that properly cooked poultry or eggs can be a source of infection.

What are the symptoms of bird flu in humans?

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

How is avian influenza detected in humans?

A laboratory test is needed to confirm avian influenza in humans.

Does the virus spread easily from birds to humans?

No. Though more than 100 human cases have occurred in the current outbreak, this is a small number compared with the huge number of birds affected and the numerous associated opportunities for human exposure, especially in areas where backyard flocks are common. It is presently not understood why some people, and not, others, become infected following similar exposures.

How does bird flu spread?

Infected birds shed flu virus in their saliva, nasal secretions, and feces. Susceptible birds become infected when they have contact with contaminated excretions or surfaces that are contaminated with excretions. It is believed that most cases of bird flu infection in humans have resulted from contact with infected poultry or contaminated surfaces. The spread of avian influenza viruses from one ill person to another has been reported very rarely, and transmission has not been observed to continue beyond one person.

Does the current seasonal influenza vaccine protect me from avian influenza?

No. Influenza vaccine for the 2005-2006 season does not provide against avian influenza.

How does H5N1 virus differ from seasonal influenza viruses that infect humans?

Of the few avian influenza viruses that have crossed the species barrier to infect humans, H5N1 virus has caused the largest number of reported cases of severe disease and death in humans. In the current situation in Asia, more than half of the people infected with the virus have died. Most cases have occurred in previously healthy children and young adults. However, it is possible that the only cases currently being reported are those in the most severely ill people and that the full range of illness caused by the H5N1 virus has not yet been defined.

Is there a vaccine to protect humans from H5N1 virus?

There currently is no commercially available vaccine to protect humans against H5N1 that is being detected in Asia and Europe. However, vaccine development efforts are taking place. Research studies to test a vaccine that will protect humans against H5N1 virus began in April 2005, and a series of clinical trials is under way.

What is the risk to people in the United States from the H5N1 bird flu outbreak in Asia and Europe?

According to the Centers of Disease Control, the current risk to Americans from the H5N1 bird flu outbreak in Asia is low. The strain of H5N1 virus found in Asia and Europe has not been found in the United States. There have been no human cases of H5N1 flu in the United States. It is possible that travelers returning from affected countries in Asia could be infected if they were exposed to the virus. Since February 2004, medical and public health personnel have been watching closely to find any such cases.

Is there a risk in handling feather products that come from countries experiencing outbreaks of avian influenza A (H5N1)?

The U.S. government has determined that there is a risk to handling feather products from countries experiencing outbreaks of H5N1 influenza.
There is currently a ban on the importation of birds and bird products from H5N1- affected countries in Africa, Asia and Europe. The regulation states that no person may import or attempt to import any birds (Class Aves), whether dead or alive, or any products derived from birds (including hatching eggs), from the following countries: Albania, Azerbaijan, Burma (Myanmar), Cambodia, Cameroon, China, Egypt, France (USDA-defined restriction zone only), India, Indonesia, Japan, Laos, Kazakhstan, Malaysia, Niger, Nigeria, Romania, Russia, South Korea, Thailand, Turkey, Ukraine and Vietnam (current as of March 15, 2006). This prohibition does not apply to any person who imports or attempts to import products derived from birds if, as determined by federal officials, such products have been properly processed to render them noninfectious so they pose no risk of transmitting or carrying H5N1 and which comply with the U.S. Department of Agriculture (USDA) requirements. Therefore, feathers from these countries are banned unless they have been processed to render them noninfectious.

Does seasonal influenza vaccine protect against avian influenza infection in people? Seasonal influenza vaccine does not provide protection against avian influenza.

Should I wear a surgical mask to prevent exposure to avian influenza?
Currently, wearing a mask is not recommended for routine use (e.g., in public) for preventing influenza exposure. In the United States, disposable surgical and procedure masks have been widely used in health-care settings to prevent exposure to respiratory infections, but the masks have not been used commonly in community settings, such as schools, businesses, and public gatherings.

Can I get avian influenza from eating or preparing poultry or eggs?
You cannot get avian influenza from properly handled and cooked poultry and eggs.
There currently is no scientific evidence that people have been infected with bird flu by eating safely handled and properly cooked poultry or eggs.
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. Even if poultry and eggs were to be contaminated with the virus, proper cooking would kill it. In fact, recent studies have shown that the cooking methods that are already recommended by the U.S. Department of Agriculture (USDA) and the Food and Drug Administration (FDA) for poultry and eggs to prevent other infections will destroy influenza viruses as well.
So to stay safe, the advice is the same for protecting against any infection from poultry:

Wash your hands with soap and warm water for at least 20 seconds before and after handling raw poultry and eggs.

Clean cutting boards and other utensils with soap and hot water to keep raw poultry from contaminating other foods.

Use a food thermometer to make sure you cook poultry to a temperature of at least 165 degrees Fahrenheit Consumers may wish to cook poultry to a higher temperature for personal preference.

Cook eggs until whites and yolks are firm.

The U.S. government carefully controls domestic and imported food products, and in 2004 issued a ban on importation of poultry from countries affected by avian influenza viruses, including the H5N1 strain. This ban still is in place.

Avian Influenza Infection in Animals

What animals can be infected with avian influenza A (H5N1) viruses?

In addition to humans and birds, we know that pigs, tigers, leopards, ferrets and household cats can be infected with avian influenza A (H5N1) viruses. In addition, in early March 2006, Germany reported H5N1 infection in a stone marten (a weasel-like mammal). It’s possible that other mammals may be susceptible to avian influenza A (H5N1) infection as well.

Can cats be infected with avian influenza viruses?

While household cats are not usually susceptible to influenza type-A infection, studies have shown that they can be infected with avian influenza A (H5N1) viruses and can spread the virus to other cats.

How do cats become infected with avian influenza A (H5N1) viruses?

All of the cases of influenza A (H5N1) infection in household cats reported to date have been associated with H5N1 outbreaks among domestic poultry or wild birds and are thought to have occurred by the cat eating raw infected meat.

What is the current risk that a cat will become infected with infected A (H5N1) virus in the United States?

Influenza A (H5N1) virus has not been identified in the United States, so at this time there is no known risk of a U.S. cat becoming infected with this virus.