What exactly is Avian Influenza (aka:Bird flu)? Basically the Bird flu is an infection caused by avian (birds) influenza (flu) viruses. These flu viruses occur naturally among wild birds. Wild birds throughout the world carry the viruses in their intestines, they generally do not get sick from them. However, bird flu is highly contagious among birds and can make some domesticated birds, such as chickens, ducks, and turkeys, very sick and even kill them.
Can any bird flu virus infect humans? Bird flu viruses do not in most circumstances infect humans, but several cases of human infection with bird flu viruses have occurred since 1997 and is very alarming.
How are human flu viruses different from bird flu viruses? There are many different sub-types of type A flu viruses. These sub-types differ because of certain proteins on the surface of the flu A virus (hemagglutinin [HA] and neuraminidase [NA] proteins). There are sixteen different HA subtypes and nine different NA subtypes of flu A viruses. Many different combinations of HA and NA proteins are therefore possible. Each combination is referred to as a different subtype. All subtypes of flu A viruses can be found in birds. However, when discussing bird flu viruses, we're referring to those flu A subtypes that continue to occur mainly in birds. They usually do not infect humans, even though we know they can. When talking about human flu viruses we are referring to those subtypes that occur widely in humans. There are only 3 known sub-types of human flu viruses H1N1, H1N2, and H3N2; it's likely that some genetic parts of current human flu A viruses came from birds originally. Flu A viruses are constantly changing and may adapt over time to infect and spread among humans.
What are symptoms of bird flu in humans? Symptoms have ranged from your typical flu-like symptoms ( cough, sore throat, fever and muscle aches) to eye infections, severe respiratory diseases, pneumonia (such as in acute respiratory distress) and other severe life-threatening complications. The symptoms of bird flu depends on which virus caused the infection.
How can bird flu spread? Infected birds shed flu virus from their saliva, nasal secretions, and feces. Susceptible birds become infected when they have contact with contaminated excretions and/or surfaces that are contaminated with excretions. It's believed that most cases of bird flu infection in humans have resulted from contact with infected poultry or contaminated surfaces.
How can bird flu in humans be treated? Recent studies suggest that the prescription medicines approved for human flu viruses would work in preventing bird flu infection in humans. However, flu viruses can become resistant to these drugs, so these medications may not always work.
What are the risks to humans from bird flu? The risk from bird flu is generally considered low to most people because the viruses occur mainly among the bird population and does not usually infect humans. However, during an outbreak of bird flu among poultry (domesticated chicken, turkeys, ducks etc.), there is a possible risk to people who have been in contact with infected birds or even surfaces that have been contaminated with excretions from infected birds. The current outbreak of Avian influenza A (H5N1) among poultry in Asia (see below) is an example of a bird flu outbreak that has caused human infections and deaths. In these situations, people should avoid contact with infected birds or contaminated surfaces and should be especially careful when handling and cooking poultry. For more information about Avian influenza and food safety issues, visit the World Health Organization website at(http://www.who.int/csr/don/en/)
What is Avian influenza A (H5N1) virus? Influenza A (H5N1) virus also referred to as H5N1 virus is an influenza A virus sub-type that occurs mainly in birds. It was first isolated from birds (terns) in South Africa in 1961. Like all bird flu viruses, H5N1 virus circulates among birds worldwide, is very contagious among birds and can be deadly.
What is the H5N1 bird flu that recently has been reported in Asia? Occurences of influenza H5N1 has recently been reported among poultry in 8 countries throughout Asia (Cambodia, China, Indonesia, Japan, Laos, South Korea, Thailand, and Vietnam) during late 2003 and early 2004. At the 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 outbreak. By March 2004, the outbreak was reported to be under control. Beginning in late June 2004, however, new deadly outbreaks of influenza H5N1 among poultry were reported by several countries in Asia (Cambodia, China, Indonesia, Malaysia [first-time reports], Thailand, and Vietnam). It is believed that these outbreaks are ongoing. Human infections of influenza A (H5N1) have been reported in Thailand, Vietnam and Cambodia.
So, what is the risk to humans from the H5N1 virus in Asia? The H5N1 virus very rarely infect humans. In 1997, the first case of spread from a bird to a human was seen during an outbreak of bird flu in poultry in Hong Kong. The virus caused severe respiratory illness in 18 people, 6 of whom later died. Since that time, there have been other reported cases of H5N1 infection among humans. Most recently, human cases of H5N1 infection have occurred in Thailand, Vietnam and Cambodia during large H5N1 outbreaks in poultry. The death rate for these reported cases has been about 50 percent. Most of these cases occurred from contact with infected poultry or contaminated surfaces; however, it is thought that a few cases of human-to-human spread of H5N1 have occurred.
So far, spread of H5N1 virus from human to human has been rare and spread has not continued beyond one person. However, because all influenza viruses have the ability to mutate (change), scientists are very concerned that the H5N1 virus could one day be able to infect humans and 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 infect people and spread easily from person to person, an influenza pandemic (worldwide outbreak of disease) could begin. No one can predict when a pandemic might occur. However, experts from around the world are watching the H5N1 situation in Asia very closely and are preparing for the possibility that the virus may begin to spread more easily and widely from person to person.
How will the H5N1 virus in humans be treated? The H5N1 virus currently infecting birds in Asia that has caused human illness and death 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 flu caused by the H5N1 virus, though studies still need to be done to prove that they work.
Is there currently a vaccine to protect humans from H5N1 virus? There currently is no vaccine to protect humans against the H5N1 virus that is being seen in Asia. However, vaccine development efforts are under way. Research studies to test a vaccine to protect humans against H5N1 virus began in April 2005. (Researchers are also working on a vaccine against H9N2, another bird flu virus subtype.) For more information about the H5N1 vaccine development process, visit the National Institutes of Health website at http://www.nih.gov/.
What is the risk to people in other countries such as the United States from the H5N1 bird flu outbreak in Asia? The current risk to others from the H5N1 bird flu outbreak in Asia is low. The strain of H5N1 virus found in Asia has not been found outside Asia. There have been no human cases of H5N1 flu for example in the United States. It is possible that travelers returning from affected countries in Asia could be infected. Since February 2004, medical and public health personnel have been watching closely to find any such cases.
What does CDC (http://www.cdc.gov/flu/) recommend regarding the H5N1 bird flu outbreak in Asia? In February 2004, the CDC provided U.S. health departments with recommendations for enhanced surveillance (detection) in the United States of avian influenza A (H5N1). Follow-up messages (Health Alert Network) were sent to the health departments on August 12, 2004, and February 4, 2005, both reminding health departments about how to detect, diagnose, and prevent the spread of avian influenza A (H5N1). It also recommended measures for laboratory testing for H5N1 virus. CDC currently advises that travelers to countries in Asia with known outbreaks of influenza A (H5N1) 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.