S. Ip Jessica F. Frost C. LeAnn White Michael J. Murray Paul J. Carney Xiang-Jie Sun James Stevens Min Z. Levine Jacqueline M. Katz Zhu-Nan Li 2014 <p>Sporadic epizootics of pneumonia among marine mammals have been associated with multiple animal-origin influenza A virus subtypes (1&ndash;6); seals are the only known nonhuman host for influenza B viruses (7). Recently, we reported serologic evidence of influenza A virus infection in free-ranging northern sea otters (<i>Enhydra lutris kenyoni</i>) captured off the coast of Washington, USA, in August 2011 (8). To investigate further which influenza A virus subtype infected these otters, we tested serum samples from these otters by ELISA for antibody-binding activity against 12 recombinant hemagglutinins (rHAs) from 7 influenza A hemagglutinin (HA) subtypes and 2 lineages of influenza B virus (Technical Appendix Table 1). Estimated ages for the otters were 2&ndash;19 years (Technical Appendix Table 2); we also tested archived serum samples from sea otters of similar ages collected from a study conducted during 2001&ndash;2002 along the Washington coast (9).</p> application/pdf 10.3201/eid2005.131890 en Centers for Disease Control and Prevention Serologic evidence of influenza A(H1N1)pdm09 virus in northern sea otters article