Pandemic H1N1 influenza virus is of global health concern and is currently the predominant influenza virus subtype circulating in the southern hemisphere 2010 winter. The virus has changed little since it emerged in 2009, however, in this report we describe several genetically distinct changes in the pandemic H1N1 influenza virus. These variants were first detected in Singapore in early 2010 an...

Three antigenic determinants were revealed in H3 hemagglutinin of influenza A viruses isolated from 1968 to 1975. One of them was common for all viruses, and two others specified differences between the viruses possessing H3 hemagglutinin.

Between September 2011 and January 2012, influenza activity was reported in Africa, the Americas, Asia, Europe and Oceania. Influenza A(H1N1)pdm09 viruses circulated at very low levels in general with the exception of some countries in Asia and the Americas. Influenza A(H3N2) viruses were predominant in Europe, many countries in the Americas and northern Africa and some countries in Asia. Influ...

Surveillance for influenza virus in pigs in the United Kingdom during spring 2010 detected a novel reassortant influenza virus. This virus had genes encoding internal proteins from pandemic (H1N1) 2009 virus and hemagglutinin and neuraminidase genes from swine influenza virus (H1N2). Our results demonstrate processes contributing to influenza virus heterogeneity.

Although influenza activity in the United States remained low from October through mid-January, the number and percentage of specimens testing positive for influenza viruses have increased in recent weeks. Laboratory-confirmed influenza infections have been reported from 45 states. The predominant influenza viruses isolated this season have been type A (H3N2) viruses that are well matched by th...

Zoonotic influenza viruses continue to be identified and evolve both genetically and antigenically, leading to the need for update of candidate vaccine viruses for pandemic preparedness purposes. Evaluation of the genetic and antigenic characteristics of these viruses, their relationship to existing candidate vaccine viruses, and their potential risks to public health, justify the need to selec...

In theory, influenza viruses can be transmitted through aerosols, large droplets, or direct contact with secretions (or fomites). These 3 modes are not mutually exclusive. Published findings that support the occurrence of aerosol transmission were reviewed to assess the importance of this mode of transmission. Published evidence indicates that aerosol transmission of influenza can be an importa...