Since its identification in April 2009, an A(H1N1) virus containing a unique combination of gene segments from both North American and Eurasian swine lineages has continued to circulate in humans. The lack of similarity between the 2009 A(H1N1) virus and its nearest relatives indicates that its gene segments have been circulating undetected for an extended period. Its low genetic diversity suggests that the introduction into humans was a single event or multiple events of similar viruses. Molecular markers predictive of adaptation to humans are not currently present in 2009 A(H1N1) viruses, suggesting that previously unrecognized molecular determinants could be responsible for the transmission among humans. Antigenically the viruses are homogeneous and similar to North American swine A(H1N1) viruses but distinct from seasonal human A(H1N1).

dx.doi.org/10.1126/science.1176225, hdl.handle.net/1765/25228
Science
This work was funded by the European Commission 7th Framework Programme; grant id fp7/223498 - European management platform for emerging and re-emerging infectious disease entities (EMPERIE)
Erasmus MC: University Medical Center Rotterdam

Garten, R, Davis, C.T, Russell, C.A, Shu, B, Lindstrom, S, Balish, A, … Cox, N.J. (2009). Antigenic and genetic characteristics of swine-origin 2009 A(H1N1) influenza viruses circulating in humans. Science, 325(5937), 197–201. doi:10.1126/science.1176225