Avian Influenza Information Sheet NORAD-USNORTHCOM Surgeon General

Avian Influenza (AI), aka “bird flu,” is caused by influenza type A viruses. H5N1 is the subtype currently circulating. H5N! can be highly pathogenic (HPAI) or of low pathogenicity (LPAI); HPAI is the type infecting and killing humans. AI occurs naturally among birds worldwide. Wild birds are often carriers, but do not usually become ill.

AI spreads easily among birds and can sicken and kill some domesticated birds (e.g. chickens, ducks, and turkeys). AI viruses do not usually infect humans, though nearly 250 WHO confirmed cases of human infection with the H5N1 virus have occurred since 2003. AI viruses are constantly mutating and might adapt over time to infect and spread among humans.

These WHO confirmed human AI cases have occurred in ten countries: Azerbaijan, Cambodia, China, Djibouti, Egypt, Indonesia, Iraq, Thailand, Turkey and Vietnam. No human cases have been identified in the United States.

Transmission
The AI virus is transmitted to people most commonly during outbreaks of AI among domestic poultry. People have become ill following close contact with the bodily secretions/excretions of sick poultry and undercooked poultry products; rarely, exposures are unclear. We suspect a few cases occurred via human-to-human transmission.

Symptoms
Symptoms range from typical flu-like fever, cough, sore throat and muscle aches to eye infections, pneumonia and other complications such as severe respiratory distress requiring ventilation support.

Treatment and Prevention
Antiviral medications might help in the treatment and prevention of AI, although flu viruses can and do become resistant to these drugs. AI is resistant to amantidine and rimantidine; newer drugs called oseltamivir (Tamiflu) and zanamivir (Relenza) might work for treatment and prevention (studies are pending).

DoD has stockpiled 2.4 million treatment courses of Tamiflu in three locations: (1) Defense Depot Susquehanna Pennsylvania (40%), (2) USAMMCE Germany (30%), (3) Defense Depot Yokosuka Japan (30%). DoD is distributing an additional 470,000 treatments to military treatment facilities. Additional Tamiflu and Relenza will be added to the stockpiles in 2007.

CDC has enough to treat 2.2 million adults and 100,000 children. Canada describes its stockpile in terms of prophylaxis (protection to prevent infection) vice treatment. Canada’s DND has Tamiflu stockpiles sufficient to protect 68,000 people or the entire DND force for 45 days, and has begun to stockpile Relenza.

Other treatment is supportive: oxygen, artificial ventilation, fluids, and treatment of secondary bacterial infection. An H5N1 vaccine has been developed, but is not licensed. HHS and DoD are stockpiling the vaccine; DoD has purchased 1.67 million doses. There is no guarantee this vaccine will work for the viral strain that causes a pandemic. Mass vaccine production takes 6-9 months using current techniques; more rapid production techniques may be available in 3-5 years.

Personal preventive measures are the most effective prevention method: avoid exposure to sick poultry, wash hands frequently, cover coughs and sneezes, avoid others when sick.

Morbidity and Mortality

True morbidity and mortality is difficult to determine given inadequate public health and surveillance systems in most of the countries currently affected. The morbidity and mortality appear high (over 50% mortality) in recognized cases. Evidence indicates some infections can cause minor illness (in Turkey) and/or go undetected (e.g. Japanese poultry workers). In a severe pandemic, experts estimate the U.S. will have 90 million people ill and 2 million of those will die. In a mild pandemic, experts estimate 100,000 people will die.

Sources & Additional information

Current as of 16 September 2006
Developed by CDR Tanis M. Batsel, Chief, Preventive Medicine.

Back