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CDC reports significant increase in cases of influenza A/H3N2
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There has been a significant increase in the number of influenza A/H3N2 variant cases since last week, according to a CDC press briefing today.
As of August 9, there have been 145 confirmed cases of the virus since the outbreak began in July 2011. As reported in Infectious Disease News last week, the total number of cases reported was 29.
“This is clearly a significant increase,” Joseph Bresee, MD, medical epidemiologist in the influenza division at the CDC, said during the briefing. “There have been changes in reporting that account for this increase. CDC is now allowing states to confirm their own H3N2 variant cases, as opposed to waiting for laboratory confirmation from the CDC.”
Bresee said that cases found positive at the state level were overwhelmingly being confirmed at the CDC. In the context of an outbreak situation, the CDC thought it was appropriate for states to report their cases as confirmed cases, as opposed to waiting for CDC confirmation.
“Positive samples are still being tested at the CDC where they will be confirmed with genetic sequencing,” Bresee said. “But we anticipate that the change in reporting requirements will provide for a more real-time indication of how these outbreaks are evolving. CDC anticipates that most, if not all, reports by states will be confirmed by CDC.”
At this point, Bresee said, there has been no evidence of human-to-human spread of H3N2 variant cases recently, though limited human-to-human transmission has occurred in the past. CDC expects that some human-to-human spread will occur in certain outbreaks, he said.
“CDC understands that people are concerned about the rapid jump in the number of cases compared to last week,” Bresee said. “This is not a pandemic situation. CDC is continuing to monitor the situation closely and will provide updates frequently.”
The confirmed cases all had had exposure to swine. The illness continues to resemble that of seasonal influenza. Most of the cases have been reported in children. The CDC has not received any reports of death. There have been two confirmed hospitalizations, but both patients have recovered and discharged.