Avian influenza, also known as 'bird flu', is a disease primarily affecting birds and is caused by a virus of the Orthomyxoviridae family.
According to its subtype, it may be classified as high or low pathogenicity, presenting different symptoms in infected birds. The Low Pathogenic Avian Influenza Virus (LPAIV) can cause a mild illness, often unnoticed or without any symptoms. The Highly Pathogenic Avian Influenza Virus (HPAIV) caused by subtypes (H5 and H7) of type A, causes serious illness in birds that can spread rapidly, resulting in high death rates in different species of birds.
Most of the influenza viruses circulating in birds are not zoonotic. However, some HPAI strains have the ability to infect humans, posing a threat to public health. The main risk factor is the direct or indirect exposure to infected animals or environments and surfaces contaminated by feces.
- Efforts to control the spread of avian influenza in Asian countries since 2003 have led to the death or destruction of more than 150 million chickens, with economic losses estimated at $10 billion.
- First identified in Hong Kong in 1997, where it caused 18 human cases with 6 fatalities, the highly pathogenic H5N1 virus has continued to spread and evolve among avian species.
- Avian influenza is by nature a transboundary disease, traveling along specific routes with migratory birds.
- Despite country control measures, avian influenza continues to spread, causing heavy losses, threatening the livelihood of poor livestock farmers and potentially impeding trade between countries.
- While the Region of the Americas has not been affected by the current Avian Influenza A/(H5N1) epidemic, there have been sporadic outbreaks of highly pathogenic Avian Influenza of the H5 and H7 subtypes detected and contained in Canada, the US, Mexico and Chile in the past 40 years.
The emergence of pathogenic infectious diseases in the past twenty years and recent outbreaks of zoonotic diseases have increasingly drawn public attention to the fact that diseases move back and forth among species. Of the 1,415 known human pathogens, 61% are zoonotic. Among other things, it is estimated that the increase of emerging and reemerging livestock disease outbreaks around the world since the mid-1990s has cost the world $80 billion. A major factor in the emergence of new zoonoses is the closer contact with wildlife of both humans and their domesticated animals, caused in particular by increasing encroachment into wildlife habitats. Other general factors include environmental changes, globalization of food production and trade, microbiological adaptation, and human behavioral factors.
The globalization of travel and trade and faster exchanges of people and products between countries allow for rapid dissemination of infectious diseases from their initial focus. It is difficult to estimate the burden of zoonoses on human health, particularly because endemic infections are largely under-reported around the world. It is undeniable, however, that emerging zoonoses have both direct (in terms of morbidity and mortality) and indirect (in terms of their impact on public health practice and structure) implications on public health.
The Pan American Health Organization (PAHO), has drafted a strategic and operational plan to support Member States in responding to pandemic influenza, based on WHO’s preparedness plan. PAHO has a long tradition of collaborating on health and agriculture through the organization of the Ministerial Level Inter-American Meeting on Health and Agriculture (RIMSA). Every two years, PAHO discusses agreements with agriculture organizations such as the IICA, and joint activities with the veterinary services in countries for the elimination of foot-and-mouth disease, zoonoses, and food safety. In particular, the RIMSA meeting, which has been organized by PAHO for more than 20 years, provides a unique regional forum that brings together the highest level of representatives from the health and agriculture sectors along with the participation of the private sector to discuss themes of common interest. Avian Influenza was included in the agenda of the 14th RIMSA meeting in Mexico in April 2005.
PAHO’s strategic and operational plan for responding to pandemic influenza includes guidelines for each phase of the potential pandemic. In particular, it includes in the pre-pandemic phase the necessary characteristics of an assessment of the countries’ capacity in responding to the threat. This assessment should involve the participation of all sectors concerned with the preparedness to a possible human pandemic, including human and animal surveillance, health services, zoonosis, agriculture, disaster, civil defense, and communication.