In Poultry:
  • Mortality may be very high (95% or higher)
  • Sudden death without clinical signs
  • Lack of energy and appetite
  • Decreased egg production
  • Soft-shelled or misshapen eggs
  • Swelling of the head, eyelids, comb, wattles, and hocks
  • Purple discoloration of the wattles, combs, and legs
  • Nasal discharge
  • Coughing, sneezing
  • Lack of coordination
  • Diarrhea


Worldwide, there are many strains of avian influenza (AI) virus that can cause varying amounts of clinical illness in poultry. AI viruses can infect chickens, turkeys, pheasants, quail, ducks, geese and guinea fowl, as well as a wide variety of other birds. Migratory waterfowl have proved to be a natural reservoir for the less infectious strains of the disease known as low pathogenicity avian influenza.

AI viruses can be classified into low pathogenicity (LPAI) and high pathogenicity (HPAI) based on the severity of the illness they cause. HPAI is an extremely infectious and fatal form of the disease that, once established, can spread rapidly from flock to flock. However, some LPAI virus strains are capable of mutating under field conditions into HPAI viruses.

Since 1997, HPAI viruses that are characterized by the H5N1 subtype have “jumped” the species barrier and infected a small number of humans in Asia. There is fear that this virus might adapt to cause a human pandemic of influenza as potentially devastating as the 1918 epidemic of Spanish Influenza which is estimated to have killed in excess of 50 million persons.

Florida has a large and profitable poultry industry with production units distributed throughout the state. The worldwide presence of avian influenza virus of all subtypes in wild birds precludes eradication of the virus. The intercontinental movement of the HPAI viruses by migratory birds poses a constant threat to the poultry industry. One of the major flyways for migratory birds in North America covers Florida.

A major outbreak of HPAI would be costly to the poultry industry, consumers, and taxpayers. Eradication of an HPAI outbreak that occurred during 1983 and 1984 in the northeastern United States resulted in the destruction of more than 17 million birds at a cost of nearly $65 million. This outbreak also caused retail egg prices to increase by more than 30 percent.


When avian influenza infections of the H5 and H7 subtypes are detected in poultry in the USA (irrespective of whether they are the low pathogenicity or high pathogenicity types), the affected flocks are depopulated. Affected birds are never treated. Vaccination against these subtypes is generally not permitted in the USA.

The importation to the USA of live poultry, caged pet birds, and poultry products is strictly controlled to minimize the introduction of HPAI viruses.