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Recent zoonoses caused by influenza A viruses
1Virology Department, Veterinary Laboratories Agency-Weybridge, New Haw, Addlestone, Surrey KT15 3NB, United Kingdom.
Revue Scientifique Et Technique (International Office of Epizootics)
|February 24, 2001
Summary
Influenza viruses, types A, B, and C, cause contagious illness. Influenza A, with subtypes like H1N1 and H3N2, can cause pandemics, with pigs potentially acting as intermediaries for avian-to-human transmission.
Area of Science:
- Virology
- Epidemiology
- Immunology
Background:
- Influenza is a contagious acute illness affecting humans and animals, caused by Orthomyxoviridae viruses.
- Influenza A viruses, with their surface glycoproteins haemagglutinin (HA) and neuraminidase (NA), exhibit significant variation and can cause devastating pandemics.
- Antigenic shift and drift are key mechanisms driving influenza evolution and epidemics, with avian species suspected as the ultimate source of influenza A viruses.
Purpose of the Study:
- To provide a comprehensive overview of influenza viruses, their classification, and their impact on human and animal health.
- To discuss the mechanisms of influenza evolution, including antigenic shift and drift, and the origins of pandemic strains.
- To highlight the role of pigs as potential intermediaries in the transmission of avian influenza viruses to humans.
Main Methods:
- Review of existing literature on influenza virus classification, evolution, and epidemiology.
- Analysis of historical pandemic events and their associated influenza A subtypes (e.g., H1N1, H2N2, H3N2).
- Examination of phylogenetic studies and evidence for interspecies transmission, particularly involving avian and swine populations.
Main Results:
- Influenza viruses are classified into types A, B, and C, with Influenza A having numerous HA and NA subtypes.
- Antigenic shift and drift lead to frequent epidemics and occasional pandemics, with four major pandemics in the 20th century.
- Pigs are identified as a key potential intermediary for the reassortment and transmission of avian influenza viruses to humans, as seen with H1N1 strains.
Conclusions:
- Influenza remains a significant global health threat, necessitating ongoing surveillance and control measures.
- Understanding viral evolution mechanisms is crucial for predicting and preventing future influenza pandemics.
- The role of animal reservoirs and interspecies transmission highlights the importance of a "One Health" approach to influenza control.