Pediatricians and other clinicians should be on the lookout for influenza in patients with recent exposure to pigs after 2 cases of swine-origin influenza were identified in children late this summer, according to the national Centers for Disease Control and Prevention (CDC).

The 2 cases—1 in Indiana and 1 in Pennsylvania—have not been epidemiologically linked. Although the 2 cases are similar to 8 other swine-origin influenza A (H3N2) cases in the last 2 years, a key difference is that 1 of the 8 gene segments (matrix [M] gene) is from the 2009 influenza A (H1N1) virus, according to a CDC report. That genetic combination is unique and has not been reported previously in either swine or humans, so no information is currently available on how efficiently the virus will be able to transmit in swine and humans or between species, the report said. Genome sequencing is underway to completely characterize the genetic composition of these 2 swine influenza isolates.

The 2009 virus hit children particularly hard. The CDC estimates that the pandemic virus caused 1,000 pediatric deaths in 2009-2010.

If influenza is suspected with possible exposure to swine, the CDC is asking clinicians to obtain a nasopharyngeal swab and send it to a state public health laboratory for quick analysis. Also, empiric neuraminidase inhibitor antiviral treatment should be considered to quickly limit potential human transmission. Viruses in the 2 patients are resistant to amantadine and rimantadine but are susceptible to the neuraminidase inhibitor drugs oseltamivir and zanamivir, according to the report.

During the time that the influenza cases were confirmed, both Indiana and Pennsylvania had low levels of influenza activity.

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