CDC details human-to-human H3N2 transmission

On Thursday, the U.S. Centers for Disease Control and Prevention released an initial assessment of the 2010-11 flu season, giving details of swine-origin novel H3N2 infections, including probable human-to-human transmission.

In the report, the CDC said that the man was exposed to pigs six days before he got sick and a respiratory sample yielded a novel H3N2 strain. Serologic tests on his daughter that were conducted six weeks later showed that she had become sick from the same virus despite no direct exposure to swine, CIDRAP News reports.

The CDC said the daughter probably contracted the virus from close contact with her father. When the CDC had first reported on the father’s infection, it noted that human-to-human spread had not been detected but that investigation was ongoing. Human infections with swine-origin flu viruses are rare and a human-to-human transmission is even more unusual. Serologic tests on additional family members who were sick at the same time were negative or inconclusive.

The report said that flu patterns during the current season resembled a more typical flu year compared with the pandemic flu patterns the previous season, CIDRAP News reports. The H3N2 virus had a dominant position despite a late rally from the 2009 H1N1 virus.

Overall, the flu season peaked in late February when 44 states reported widespread activity of influenza. The 2010-11 season was said to be less severe than the previous season and the 2007-09 season but more severe than 2008-09. The flu vaccine was also tested to be a good match with the circulating strains.