Influenza A(H1N1)pdm09 virus infection in marine mammals in California.

摘要: Dear Editor, In a recent report, some of the coauthors this letter documented isolation influenza A(H1N1)pdm09 from northern elephant seals (NES, Mirounga angustirostris) in California 2010.1 The two virus sequences were most similar to December 2009 human isolate San Diego, California, raising many questions as timing and extent transmission among marine mammals. This presents new data showing that three co-occurring mammal species exposed early 2009, widespread epidemic subsequently occurred NES, but not harbor (HS, Phoca vitulina) or sea lions (CSL, Zalophus californianus). Over 300 000 live eastern North Pacific Ocean haul out molt give birth along mainland island coastlines California. We obtained sera abundant pinniped region, tested them for presence A(H1N1)pdm09-specific antibodies by hemagluttination inhibition (HI). chose samples NES (n=222), CSL (n=183) HS (n=140) belonging populations spanned US coastline Mexico Oregon determine if exposure was limited small region population examined previously.1 also selected covered period 2009–2011 examine emergence relative its first reported detection humans (2009) (2010). Samples included free-ranging animals had minimal contact sampled on Channel Islands off coast southern stranded central hospitalized at Marine Mammal Center. In addition determining timing, host range, geographic exposure, we investigated whether endemic NES. focused surveillance efforts females their pups Southern since 75% extant >170 breed these islands.2 collected nasal rectal swabs serum 20 nursing mothers Nicolas Island January 2012 when 2∼4 weeks old, resampled same month later February after they weaned. another 15 single time Miguel 2012. Swabs each animal placed viral transport media matrix real-time polymerase chain reaction inoculation embryonating chicken eggs, HI. This study shows emerged mammals multiple produced (Table 1). Seropositive detected seropositive 2010. In contrast CSL, appeared be uniquely susceptible infection transmission, with occurring regions far beyond where isolated By 2011, 48% 1000 km HI titers ≥40, 54% adult 63% high percentage HI-positive results is due intrinsic background serum, previous clearly negative against other strains.1 Table 1 Antibodies USA, 2009–2012 In Island, there trend all increase age (i.e., pre-weaning post-weaning), 30% (6/20) twice showed four-fold titer over one-month period. consistent an anamnestic antibody response acute infection, could explained gradually accumulating maternal antibodies.3 Positive/negative largely correlated between pups, further supporting hypothesis transfer. No evidence A viruses RNA swabs, thus it appears unlikely colony 2012. Although HS, no transfer comparable seen Four 60 Center 2010, positive adults 2011 (n=50). Likewise, seven sub-adult 2010 (n=90). We hypothesize reduced genetic variability species-specific attributes may influence susceptibility species. underwent severe demographic bottleneck, recovering estimated total 170 today, studies have shown virtual lack nuclear mitochondrial loci.4,5,6 suggested attach poorly respiratory epithelium mammals, are available NES.7 Marine especially true (Phocidae) like play role swine reservoirs mixing hosts avian mammalian viruses.8 outbreak avian-origin H3N8 Atlantic (Phoca east coast, reports seal elsewhere, support hypothesis.9,10,11,12,13,14,15 However, sudden appearance rapid spread highly contagious both unprecedented. potential co-infected origin creates troubling opportunities reassortment virulent genotypes.