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CDC: Number of H3N2v cases continuing to rise

Friday August 10, 2012
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The Centers for Disease Control and Prevention issued a report Friday on the growing number of cases of influenza A (H3N2) variant and an evaluation of rapid influenza diagnostic tests for the detection of the virus.

From July 12 to Aug. 9, the CDC received reports of 153 cases of H3N2v infections, including 120 in Indiana and 31 in Ohio. Of the 138 reported cases for which demographic information was available, 128 occurred in people younger than 18. The median age of patients was 7. Two people were hospitalized as a result of their illness, and no deaths occurred.

One patient, in Hawaii, was exposed to swine on the job, and no additional illnesses were found in the state. The 152 other patients resided in 27 counties in Indiana, Ohio and Illinois, and all reported direct or indirect exposure to swine at agricultural fairs or in other settings.

"At this point, thereís no evidence of sustained efficient human-to-human spread in the community," said Joseph Bresee, MD, FAAP, chief of the Epidemiology and Prevention Branch in the CDCís Influenza Division. "This is not a pandemic situation. But of course, CDC is continuing to monitor the situation closely."

Bresee said "limited human-to-human transmission has been observed in the past and we expect some limited human-to-human spread may be observed in these current outbreaks." He said cases so far have been mostly mild, but more severe illness is possible as is the case with seasonal influenza.

Children younger than 5, adults 65 and older, pregnant women and people with chronic medical conditions or weakened immune systems are at increased risk for influenza complications and should avoid exposure to pigs and swine barns this summer, especially if ill swine have been identified, according to the researchers.

"Clinicians should consider antiviral treatment with oral oseltamivir or inhaled zanamivir in patients with suspected or confirmed H3N2v infection," the reportís authors wrote. "Antiviral treatment is most effective when started as soon as possible after influenza illness onset."

Diagnosis and detection

H3N2v viruses can be detected by qualified U.S. public health laboratories using the CDC Flu rRT-PCR Dx Panel, which is available in public health laboratories but is not a point-of-care test available to clinicians. Rapid influenza diagnostic tests frequently are used for the diagnosis of influenza infection in clinical settings, and the recent outbreaks of H3N2v virus have highlighted the need to evaluate commercially available, widely used tests for their ability to detect H3N2v viruses, according to the CDC.

As an initial assessment, CDC conducted an evaluation of seven Food and Drug Administration-approved RIDTs with seven H3N2v viruses. Of the seven tests, Directigen, Sofia, Veritor and Xpect detected all influenza A (H3N2)v viruses. BinaxNOW detected five of seven, and QuickVue detected three of seven. FluAlert detected only one of seven.

"Enhanced surveillance for influenza H3N2v virus infection is indicated, especially in regions and states with confirmed H3N2v cases," wrote the authors of the report.

"The initial goal of enhanced surveillance is to detect the source and geographic spread of these viruses, but once cases are detected, particular emphasis should be placed on detection of ongoing transmission within the community through investigation of close contacts of patients with confirmed cases. In addition, surveillance in hospitals will be important to determine whether severe illnesses are occurring as result of H3N2v infections."

Those "with increased risk for complications who develop influenza-like illness should see their healthcare provider promptly to determine whether treatment with antiviral medications is warranted," the authors wrote.

To read the full report, visit http://1.usa.gov/QWUrk4.

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