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Food Safety Focus (67th Issue, February 2012) – Food Safety Platform

The Fowl, Avian Flu and the Food

Reported by Dr. Benedict TSANG, Veterinary Officer,
Veterinary Public Health Section,
Centre for Food Safety

In the pervious issue of Food Safety Platform, we briefly introduced why animal diseases that are transmissible to humans (zoonosis) became a concern in food safety. This time, let's take a look at a zoonotic disease that has often grabbed news headlines in recent years — Avian Influenza (AI).

Avian Influenza - A Known Public Health Threat

The catastrophic potential of avian influenza (or bird flu) on human beings was well-recognised by the Hong Kong people since the first local human H5N1 case detected in 1997. That year, 18 confirmed cases with six deaths were reported and the outbreak was finally controlled by a territorywide slaughter of more than one million chickens. To date, avian influenza is still an important public health threat with a few to a hundred human infections annually over the past decade throughout the world. Diagram 1 shows the cumulative number of confi rmed human cases of H5N1 worldwide since 2003.

Diagram 1. Areas with confirmed human cases of H5N1 since 2003, according to World Health Organization as of 24 January 2012.
Diagram 1. Areas with confirmed human cases of H5N1 since 2003, according to World Health Organization as of 24 January 2012.

Avian Influenza Connecting Birds and Humans

Avian influenza caused by the influenza virus type "A" affects mainly birds including chickens, turkeys, quails, guinea fowl, etc. There are many different strains of AI virus (such as H5N1, H5N2, H7N7, H9N2, etc.). Most of them are found naturally among birds, particularly waterfowl and shorebirds, around the world. These birds normally carry the viruses in their respiratory or intestinal tracts and usually do not get sick (asymptomatic infection), and are often viewed as reservoirs for AI viruses. While most of the AI viruses can only cause mild clinical infection in domestic poultry, others, called highly pathogenic strains, can kill up to 90–100 per cent of poultry in a flock. The notorious H5N1 is one of such highly pathogenic strains.

Infected birds can shed AI viruses in their saliva, nasal secretions, and faeces. Susceptible birds become infected when they have contact with excreta from infected birds, or through contaminated fomites. Though avian influenza is usually highly species-specific, on rare occasions, few of them may have the abilities to cross the species barrier to infect human and bring serious outcomes including death.

Safeguarding Food Safety from Avian Influenza

There is no evidence to suggest that the AI virus can be transmitted to humans through consumption of properly prepared poultry or eggs. Most human infections with AI viruses have occurred following direct or indirect exposure to infected live or dead poultry or contaminated environments. To this end, slaughtering, defeathering, handling carcasses of infected poultry, and preparing those poultry for consumption, especially in household settings, are more important risk factors.

To address these risk factors, the Food and Environmental Hygiene Department and the Agriculture, Fisheries and Conservation Department have been working together in implementing a series of comprehensive measures to guard against the occurrence and spread of avian influenza at farm, border, wholesale and retail levels.

Besides, the Centre for Food Safety (CFS) also makes reference to the science-based standards, guidelines and recommendations provided by the World Organization for Animal Health (OIE) to safeguard food safety from AI. Suspension of import of poultry and their products from countries or regions affected by AI would be implemented once notified.

Health Begins at Home

To protect against a range of common and rare diseases including avian influenza transmissible through raw or undercooked poultry, you can begin your healthy life right away. Avoid any direct contact with live poultry and their faeces. Refuse eating any raw or undercooked poultry meat and eggs. Always observe good personal, food and environmental hygiene. For more information, please visit the CFS website.