This article is more than 5 years old. Information may no longer be current.
CDC: Influenza activity low this summer
Click Here to Manage Email Alerts
The United States experienced relatively low levels of influenza activity from May 20 to Sept. 22, although more seasonal influenza viruses were identified compared with the summer months of past years, according to a recent report from the CDC.
Since July 12, 306 cases of human infections with influenza A (H3N2) variant viruses (H3N2v) have been reported to the CDC from 10 states, resulting in 16 hospitalizations and one death. Most cases were the result of direct contact with swine. H3N2 viruses identified from swine were genetically similar to H3N2v viruses identified in human cases, according to results in the Morbidity and Mortality Weekly Report.
The first H3N2v viruses this season were discovered in Indiana, which had 138 human cases. Other states affected included Hawaii (one), Illinois (four), Maryland (12), Michigan (six), Minnesota (four), Ohio (107), Pennsylvania (11), West Virginia (three) and Wisconsin (20).
“Suspected human-to-human transmission has been identified in a small number of cases, but ongoing community transmission of this virus has not been detected,” the MMWR report said.
According to the CDC, 93% of patients were aged younger than 18 years, and 52% were female.
As a result of heightened surveillance for H3N2v, three cases of human infection with the influenza A (H1N2) variant (H1N2v) virus and one case of influenza A (H1N1) variant (H1N1v) virus were reported to the CDC. The four patients reported direct contact with swine; one patient was hospitalized and all four have recovered.
The CDC reported that most influenza A viruses were “well-matched” to this season’s recommended vaccine. However, of the 42,562 respiratory specimens examined, 7% tested positive for influenza, indicating higher levels of influenza activity vs. previous summers.
Excluding the summer during the 2009 pandemic, an average of 1.3% of specimens tested positive for influenza during the past 6 years. Of the 2,986 specimens that tested positive for influenza this summer, 50% were influenza A viruses and 50% were influenza B viruses.
Elsewhere, the seasonal patterns of influenza in countries located in the Southern Hemisphere were typical for those regions, according to the CDC.
“Annual influenza vaccination remains the best method for preventing influenza and its associated complications, but the 2012-13 seasonal influenza vaccine does not provide protection against the H3N2v virus,” the report said. “Treatment with influenza antiviral medications is recommended as early as possible for patients with confirmed or suspected influenza (either seasonal influenza or variant influenza infection) who have sever, complicated, or progressive illness; who require hospitalization; or who are at risk for influenza-related complications.”
Click Here to Manage Email Alerts