Great concern has arisen over the continued infection of humans with highly pathogenic avian influenza (HPAI) of the H5N1 subtype. Ongoing human exposure potentially increases the risk that a pandemic virus strain will emerge that is easily transmissible among humans. Although the pathogenicity of a pandemic strain cannot be predicted, the high mortality seen in documented H5N1 human infections thus far has raised the level of concern.
Objectives
To define the three types of influenza that can affect humans, discuss potential exposure risks at the human–animal interface, and suggest ways to reduce exposure and help prevent development of a pandemic virus.
Methods
This review is based on data and guidelines available from the World Health Organization, the scientific literature, and official governmental reports.
Results
Epidemiological data on human exposure risk are generally incomplete. Transmission of HPAI to humans is thought to occur through contact with respiratory secretions, feces, contaminated feathers, organs, and blood from live or dead infected birds and possibly from contaminated surfaces. Consumption of properly cooked poultry and eggs is not thought to pose a risk. Use of antiviral containment and vaccination may protect against development of a pandemic.
Conclusions
To most effectively decrease the risk of a pandemic, the public health and animal health sectors—those which are responsible for protecting and improving the health of humans and animals, respectively—must collaborate to decrease human exposure to HPAI virus, both by controlling virus circulation among poultry and by assessing the risks of human exposure to avian influenza virus at the human—animal interface from primary production through consumption of poultry and poultry products, and implementing risk-based mitigation measures.
ViboudCBoellePYPakdamanKCarratFValleronAJFlahaultA. Influenza epidemics in the United States, France, and Australia, 1972–1997. Emerg Infect Dis2004;10:32–9.
2.
WebsterRGBeanWJGormanOTChambersTMKawaokaY. Evolution and ecology of influenza A viruses. Microbiol Rev1992;56:152–79.
SwayneDE. Occupational and consumer risks from avian influenza viruses. Dev Biol (Basel)2006;124:85–90.
6.
PerdueMLSwayneDE. Public health risk from avian influenza viruses. Avian Dis2005;49:317–27.
7.
BeigelJHFarrarJHanAMHaydenFGHyerRde JongMDLochindaratSNguyenTKNguyenTHTranTHNicollATouchSYuenKY. Writing Committee of the World Health Organization (WHO) Consultation on Human Influenza A/H5. Avian influenza A (H5N1) infection in humans. N Engl J Med2005;353:1374–85.
8.
WebsterRGYakhnoMHinshawVSBeanWJMurtiKG. Intestinal influenza: Replication and characterization of influenza viruses in ducks. Virology1978;84:268–78.
9.
Organization for Animal Health (OIE). Hygiene and disease security procedures in poultry breeding flocks and hatcheries. Appendix 3.4.1. 2006 Terrestrial Animal Health Code. Available at: http://www.oie.int/eng/normes/mcode/en_chapitre_3.4.1.htm. Accessed 16 February 2007.
10.
MumfordEKihmU. Integrated risk reduction along the food chain. Ann NY Acad Sci2006;1081:147–52.
PerkinsLESwayneDE. Pathobiology of A/chicken/Hong Kong/220/97 (H5N1) avian influenza virus in seven gallinaceous species. Vet Pathol2001;38:149–64.
13.
SwayneDEBeckJR. Heat inactivation of avian influenza and Newcastle disease viruses in egg products. Avian Pathol2004;33:512–8.
14.
ElbersARFabriTHde VriesTSde WitJJPijpersAKochG. The highly pathogenic avian influenza A (H7N7) virus epidemic in The Netherlands in 2003—lessons learned from the first five outbreaks. Avian Dis2004;48:691–705.
KeawcharoenJOraveerakulKKuikenTFouchierRAAmonsinAPayungpornSNoppornpanthSWattanodornSTheambooniersATantilertcharoenRPattanarangsanRAryaNRatanakornPOsterhausADMEPoovorawanY. Avian influenza H5N1 in tigers and leopards. [serial online]. Emerg Infect Dis2004;10(12): 2189–91. Available at: http://www.cdc.gov/ncidod/EID/vol10no12/04-0759.htm. Accessed 13 October 2006.
19.
ThanawongnuwechRAmonsinATantilertcharoenRDamrongwatanapokinSTheamboonlersAPayungpornSNanthapornphiphatKRatanamungklanonSTunakESongsermTVivatthanavanichVLekdumrongsakTKesdangsakonwutSTunhikornSPoovorawanY. Probable tiger-to-tiger transmission of avian influenza H5N1. [serial online]. Emerg Infect Di2005;11(5): 699–701. Available at: http://www.cdc.gov/ncidod/EID/vol11no05/05-0007.htm. Accessed 13 October 2006.
20.
RimmelzwaanGFvan RielDBaarsMBestebroerTMvan AmerongenGFouchierRAOsterhausADKuikenT. Influenza A virus (H5N1) infection in cats causes systemic disease with potential novel routes of virus spread within and between hosts. Am J Pathol2006;168(1): 176–83.
21.
SwayneDE. Microassay for measuring thermal inactivation of H5N1 high pathogenicity avian influenza in naturally infected chicken meat. Int J Food Micbiol2006;108:268–71.
22.
World Health Organization/Food and Agriculture Organization. Risk assessments of Salmonella in eggs and broiler chickens. Microbiological Risk Assessment Series 2. 2002. Available at: http://www.who.int/foodsafety/publications/micro/en/salmonella.pdf. Accessed 1 March 2007.
World Health Organization. Highly pathogenic H5N1 avian influenza outbreaks in poultry and in humans: Food safety implications. INFOSAN Information Note No. 7/2005 (Rev 1.5 Dec). WHO website. Available at: http://www.who.int/foodsafety/micro/avian/en/index2.html. Accessed 16 February 2007.
Avian influenza—H5N1 infection found in a stone marten in Germany. WHO Disease Outbreak News web page (9 March 2006). Available at: http://www.who.int/csr/don/2006_03_09a/en/index.html. Accessed 16 February 2007.
30.
SongsermTAmonsinAJam-onRSae-HengNPariyothornNPayungpornSTheamboonlersAChutinimitkulSThanawongnuwechRPoovorawanY. Fatal avian influenza A H5N1 in a dog. Emerg Infect Dis2006;12(11) November 2006. Available at: http://www.cdc.gov/ncidod/EID/vol12no11/06-0542.htm. Accessed 16 February 2007.
31.
World Health Organization. Human avian influenza in Azerbaijan, February—March 2006. Wkly Epidemiol Rec2006;81:183–8.
32.
KouZLeiFMYuJFanZJYinZHJiaCXXiongKJSunYHZhangXWWuXMGaoXBLiTX. New genotype of avian influenza H5N1 viruses isolated from tree sparrows in China. J Virol2005;79:15460–6.
33.
UngchusakKAuewarakulPDowellSKitphatiRAuwanitWPuthavathanaPUiprasertkulMBoonnakKPittayawonganonCCoxNZakiSThawatsuphaPChittaganpitchMKhontongRSimmermanJChunsutthiwatS. Probable person-to-person transmission of avian influenza A (H5N1). N Engl J Med2005;352:333–40.
34.
HoffmannENeumannGKawaokaYHobomGWebsterRG. A DNA transfection system for generation of influenza A virus from eight plasmids. Proc Natl Acad Sci USA2000;97:6108–13.
35.
FodorEDevenishLEngelhardtOGPalesePBrownleeGGGarcia-SastreA. Rescue of influenza A virus from recombinant DNA. J Virol1999;73:9679–82.
36.
PleschkaSJaskunasREngelhardtOGZurcherTPalesePGarcia-SastreA. A plasmid-based reverse genetics system for influenza A virus. J Virol1996;70:4188–92.
