2012 -- The Minnesota Department of Health has reported detection of
3 infections with an influenza A H1N2 variant (“H1N2v”) virus with
the pandemic M gene from the 2009 H1N1 virus. These cases were
reportedly associated with prolonged contact with pigs at a fair.
H1N2 viruses normally circulate in pigs, not people, but rare human
infections with this virus have been detected in the past. This
virus is different from the H3N2v virus that, as of today, is
reported to have caused 296 human infections across 10 U.S. states
since July 2012. These additional human infections underscore the
fact that swine influenza viruses can spread to people after close
contact with infected pigs, and support the importance of ongoing
surveillance for both human and swine influenza viruses.
H1N2 Variant Virus Detected in Minnesota
According to the state of Minnesota, each of the 3 people infected
with the H1N2v virus had exhibited pig(s) or spent prolonged time
with pig(s) at the Minnesota State Fair. Two of the three people had
underlying health conditions that placed them at high risk of
serious flu complications; one of the two people with high risk
factors was hospitalized, highlighting again the importance of the
CDC recommendation that people with high risk factors avoid close
contact with pigs and pig arenas at fairs this season. All 3 people
have recovered from their illnesses.
People who are at high
risk of serious flu complications include children younger than 5
years, people 65 years and older, pregnant women, and people with
certain long-term health conditions (like asthma and other lung
disease, diabetes, heart disease, weakened immune systems, and
neurological or neurodevelopmental conditions). A full list of high
risk factors is available on the CDC seasonal flu site.
addition to avoiding pigs and pig arenas at fairs this year, as
always, people with high risk conditions who develop flu-like
symptoms should seek prompt medical attention. The H1N2v virus
should be susceptible to both currently recommended influenza
antiviral drugs [oseltamivir (TamifluŽ) and zanamivir (RelenzaŽ)].
CDC has confirmed the Minnesota samples as H1N2v viruses.
Sequencing of the viruses indicates these H1N2 variant viruses are
very similar to those found in humans previously; with the exception
of the addition of the pandemic M gene. This is the first time this
virus has included the M gene from the 2009 H1N1 pandemic virus when
isolated from a person. Genetic analysis shows that the
hemagglutinin (H) of this virus is similar to human seasonal
influenza viruses that circulated in people as recently as 2007, so
there would likely be protective immunity against this particular
virus in the human population.
The University of Minnesota
Veterinary Diagnostic Lab also isolated an H1N2 virus from swine
sampled at the Minnesota State Fair. Sequencing at National
Veterinary Services Laboratories in Ames, Iowa, confirmed that it
matches the human isolates from Minnesota. According to the USDA
Swine Influenza Surveillance program, very similar H1N2 viruses –
also containing the pandemic M gene – have been found in pigs since
early 2010 in Minnesota and a number of other U.S. states.
For more information about swine influenza, see Information on Swine
Influenza/Variant Influenza Viruses.