Pandemic influenza virus: tracking a three-headed monster.

摘要: Pandemic influenza poses one of the largest threats to human health. The past hundred years has witnessed 4 pandemics that caused significant morbidity and mortality: 1918 Spanish flu (H1N1), 1957 Asian (H2N2), 1968 Hong Kong (H3N2), 2009 (H1N1) flu.1 Featured in issue 6(1) Virulence, Abdelwhab Abdel-Moniem document avian-origin A viruses currently circulating reservoir hosts Egypt,2 wherein highly pathogenic avian (HPAI) H5N1 is endemic a pandemic risk.3 This provides useful paradigm for understanding molecular basis how new subtypes arise, they overcome host range barriers infect species, what precautions can be implemented slow inevitable emergence strains with potential. Influenza virus (IAV) single-stranded, enveloped RNA capable infecting wide animal addition humans.4 viral genome comprised 8 gene segments (chromosomes) encoding several products, including 2 surface proteins reciprocal functions contribute infectivity, range, virulence.5 Hemagglutinin (HA) confers adherence sialic acid receptors located on respiratory epithelium, whereas neuraminidase (NA) encodes sialidase activity releases progeny from infected cells. New arise by ‘antigenic drift’, associated minor changes either HA or NA commonly observed ‘seasonal’ strains; those via shift’, marked these (and others) occur when different recombine reassort chromosomes. Such reassortment engender which little no pre-existing immunity exists population. Avian-origin Egypt largely bird-restricted subtype prevalent asymptomatic within wild birds, infectious lethal domestic poultry. Although poor transmission humans between individuals, it fatal. Of particular concern potential evolution this toward efficient co-circulation other hosts. Insights into genesis have come analyses novel H7N9 recently reported China (2013).6 was derived H9N2 circulated poultry 20 years subsequent upon H7, N9 viruses.7 Thus, surveillance reservoirs co-circulating may origin top priority. Avian been isolated dozens species waterfowl carry asymptomatically their gut,8 frequent possible livestock.9 Avian-origin are also found lesser extent animals close contact (horses, camels, cats, dogs).10-12 Along Asia, ‘ground zero’ as lies geographically main flyways migratory birds linking Africa Europe Asia.2 increased well warranted identify highest potential.13 Once identified, culling warranted; necessary precaution vaccinated since shed absence disease.14 Important lessons learned circulation and/or hosts, necessitating thorough review surveillance, identification eradication practices led following recommendations: 1) improved hosts;13 2) banning live markets avoid contamination interspecies transmission;14 3) restricting backyard free mitigate exposure waterfowl;2 4) animals.14 Implementation recommendations will require global effort make them feasible cost, accessibility, educational standpoint, due impacts cultural, social, economic aspects long-standing husbandry practices. Moving forward, implementation likely play vital role success any comprehensive safety plan transmission.