Secondary case patients of an index patient with
influenza A/H1N1 were found to be coinfected with strains of influenza A/H1N1
and A/H3N2 that were closely related to existing strains, according to a recent
The researchers recounted the path of novel influenza
A/H1N1 from its emergence in Mexico in early 2009 to a 23-year-old patient in
central Cambodia who was diagnosed with pH1N1 in October of that year. Three
children who resided in his home and the teacher of the children then developed
a cluster of influenza-like illnesses.
Results of a genetic analysis using reverse
transcriptase polymerase chain reaction electrospray ionization mass
spectrometry indicated that two of the secondary case patients were coinfected
with influenza A/H3N2 and pH1N1. It was further determined via phylogenetic
analysis of the hemagglutinin genes from these isolated viruses that the
strains were closely related to existing pH1N1 and A/H3N2 viruses circulating
in the region, according to the results.
Patrick J. Blair, PhD, of the department of
respiratory diseases at the Naval Health Research Center in San Diego, told
Infectious Diseases in Children that the incident may be cause for
further attention to be paid to co-circulating influenza viruses. The
concern is that an easily transmissible and highly lethal influenza could
result in a novel virus and increase the risk of pandemic, Blair said.
According to the researchers, genetic recombination was
not evident within plaque-purified viral isolates on full-genome sequencing,
and dual influenza infections may reassert in areas where they are
co-circulating. They said the risk for zoonotic and seasonal influenza viruses
is suggested in this incident.
The manuscript mentions (but does not document)
the potential risk of recombination between
A/H5N1 when they coinfect a susceptible host such as swine or
humans, Blair said.