The avian flu is a strain of the influenza A virus. Bird flu is also called the “H5N1 virus” named for the reports that state the H5N1 strain as the most common among birds and humans. Though it does occur chiefly in wild birds, it has infected and killed humans since 1997. Its notoriety hit its peak in the early 2000′s, but health experts warn that the ever-mutating avian influenza virus could very well result in the next world-wide influenza pandemic.
Certain birds tend to carry the virus in their intestines without becoming sick, but when they shed the virus in their saliva, nasal secretions, and feces, they can pass the highly contagious infection on to other birds, such as water fowl, wild ducks, or poultry meant for human consumption. Fecal-to-oral transmission is the most common means of infection in birds. Of the reported human cases with avian flu, most infections are a result of contact with infected poultry, such as domesticated turkeys or chickens, or areas that infected poultry have been in. There is no evidence that human-to-human spread of avian influenza is a possibility at this time.
Avian influenza A virus strains are classified as either low pathogenic (LPAI) or highly pathogenic (HPAI). This classification is based on molecular genetic and pathogenesis criteria. Most birds who carry the virus in their intestines are carrying the LPAI strain.
While avian flu A viruses can be broken down into further subtypes, only those of the genetic sequences H5 and H7—such as H5N1, H7N7 and H7N3 viruses—have been classified as being highly pathogenic strains of avian influenza (HPAI). Humans who have been infected with HPAI have ranged from less severe strains to the more fatal strains, while humans infected with LPAI have experienced much milder symptoms, from conjunctivitis to regular influenza-like symptoms.
The following timeline is from Avian Influenza: An Internal Report for Ohio State University.
May 1997 – The avian influenza virus H5N1 is isolated for the first time in Hong Kong. The virus infects eighteen people, killing six.
February 2003 – The avian virus H5N1 infects two people in Hong Kong, killing one. Outbreaks of avian flu occur in chickens in The Netherlands (H7N7).
December 2003 – South Korea discovers avian flu in chickens (H5N1).
January 2004 – Japan has an outbreak of avian influenza (H5N1).
July 2004 – Thailand, Vietnam, China, and Indonesia, report new infections in poultry (H5N1).
October 2005 – Greece detects avian flu in a single turkey.
January 2006 – Turkey reports cases of avian flu in humans.
As of April 2012, 355 people worldwide have died from the HPAI H5N1. No one in the United States has died from avian influenza.
However, the World Health Organization (WHO) has stated that the world is now closer to another influenza pandemic than at any time since 1968. In WHO’s six phases of pandemic alert, the world is presently at phase 3 and will remain there until the new influenza virus can spread from human to human.
Symptoms of avian flu infection in humans depend largely on whether the strain is LPAI or HPAI. The most common infection among humans, the H5N1 virus, can cause typical influenza symptoms such as:
- Muscle aches
- Runny nose
- Sore throat
Of the more severe strains of HPAI, some people have been reported to also experience:
- Mild eye infection (conjunctivitis)
Cornell Lab of Ornithology: Bird Flu
A great resource, including latest news about avian flu, the effect on human health and birds, FAQs, and the top ten things to know about the virus.
Evolution and the Avian Flu
Berkley’s Understanding evolution site takes a look at the ability of viruses to evolve quickly to infect more hosts and what current studies can predict about avian flu.
Agricultural Disasters: Avian Influenza
A report from Extension Disaster Education Network (EDEN) in regards to food safety, hunting, the likelihood of infected cats, and advice to bird owners and the public.
Influenza at the Human-Animal Interface
The World Health Organization (WHO) presents statistics, figures, outbreak numbers, and other information regarding animal related influenza, such as avian flu.