Influenza 2012-13: a recap of activity
The Centers for Disease Control and Prevention have just published a summary of the activity from the recently ended seasonal influenza epidemic, as well as an assessment of the effectiveness of the vaccination program. Information from this study is currently being used to formulate vaccine composition for the upcoming seasonal flu outbreak. I charted the spread of influenza throughout the US, using the data provided by the CDC, and flu activity started early in the 2012-13 season in October and peaked in late December. The main variety of circulating virus during the season was an influenza A of the H3N2 type. The CDC notes that the past season resulted in more hospitalizations and deaths due to complications of disease than in previous years, however composition of the seasonal vaccine last year appeared to mirror very well those varieties of virus that were actually present, and much more severe morbidity and mortality were prevented by the vaccination program.
With this surveillance data in hand from the just ended influenza season, the Food and Drug Administration’s Vaccine Advisory Committee has put forward recommendations for the virus antigens that should be included in this year’s vaccine. The Tri-Valent vaccine contains portions of three influenza viruses, two from influenza A (H1N1 and H3N2) and one from influenza B (Yamagita). Although the virus choice for the H3N2 vaccine component is similar to the one used last year, the board has recommended a slightly different version to be used this year, as it appears that the virus used to create vaccine has accumulated a number of random mutations during the growth of the virus in the laboratory to make vaccines.
One potentially alarming point of data for the upcoming influenza season is the recent report from Chinese health authorities of a novel H7N9 virus, which had infect 132 people as of June 7, 2013. In each case, close contact with poultry had been reported, as opposed to the H3N2 variant from last year which had an initial association with swine. No cases outside of mainland China have been reported in the current outbreak, however it will bear very close watching due to the severe disease associated with it as 27% of the cases have been fatal.