One case of human infection with a novel influenza A virus was reported by the Iowa Department of Public Health, according to FluView, a report from the Centers for Disease Control and Prevention for the week ending Jan. 9.
The case patient had onset of symptoms in September 2009, but did not require hospitalization and has fully recovered. The virus was identified as swine influenza A (H3N2) and investigated in November 2009.
No clear exposure to swine was identified, but no evidence of sustained human-to-human transmission with this virus was found. Early identification and investigation of novel influenza A cases is critical to evaluate the extent of the outbreak and possible human-to-human transmission, the CDC said. Surveillance for human infections with novel influenza A viruses is conducted year-round.
“I think if there was other transmission going on associated with this case we would have picked it up and we haven't," CDC spokesman Tom Skinner said.
A report released July 31, 2009, by the University of Pittsburgh Medical Center described H3N2.
Since 1968, it has been the dominant strain in most influenza seasons. It has been implicated in more severe annual flu outbreaks than seasonal H1N1, and it harbors almost universal resistance to the adamantane class of drugs, the UPMC stated.
Since early 2009, the UPMC reported, the H3N2 virus has been accumulating genetic changes that may diminish the protectiveness of the seasonal influenza vaccine.
A genetically drifted variant of the H3N2 strain of virus was uncovered in March. The mutated virus was first discovered in samples taken from an influenza outbreak within a nursing facility.
The emergence of this drifted variant of H3N2 underscores the vital need for continual surveillance of influenza isolates of all subtypes, as the propensity for this virus to alter its genetic components will also pose an obstacle to crafting efficacious vaccines, the UPMC reiterated.