Avian influenza, or bird flu, is a contagious disease of animals caused by viruses that normally infect only birds and, less commonly, pigs. 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 & high extremes of virulence. The so-called “low pathogenic” form commonly causes only mild symptoms (ruffled feathers, a drop in egg production) & may easily go undetected. The highly pathogenic form is far more dramatic. It spreads very rapidly through poultry flocks, causes disease affecting multiple internal organs, & has a mortality that can approach 100%, often within 48 hours.
Travellers to areas affected by avian influenza in birds are not considered to be at elevated risk of infection unless direct & un-protected exposure to infected birds (including feathers, faeces & under-cooked meat & egg products) occurs.
WHO continues to recommend that travellers to affected areas should avoid contact with live animal markets & poultry farms, & any free-ranging or caged poultry. Large amounts of the virus are known to be excreted in the droppings from infected birds. Populations in affected countries are advised to avoid contact with dead migratory birds or wild birds showing signs of disease.
Direct contact with infected poultry, or surfaces & objects contaminated by their droppings, is considered the main route of human infection. Exposure risk is considered highest during slaughter, defeathering, butchering, & preparation of poultry for cooking. There is no evidence that properly cooked poultry or poultry products can be a source of infection.
Two drugs (in the neuraminidase inhibitors class), oseltamivir (commercially known as Tamiflu) & zanamivir (commercially known as Relenza) can reduce the severity & duration of illness caused by seasonal influenza. The efficacy of the neuraminidase inhibitors depends, among others, on their early administration ( within 48 hours after symptom onset). For cases of human infection with H5N1, the drugs may improve prospects of survival, if administered early, but clinical data are limited. The H5N1 virus is expected to be susceptible to the neuraminidase inhibitors. Antiviral resistance to neuraminidase inhibitors has been clinically negligible so far but is likely to be detected during widespread use during a pandemic.
Travellers should contact their local health providers or national health authorities for supplementary information.