What is H1N1 ( swine flu)?
H1N1 (referred to as “ swine flu” early on) is a new influenza virus causing illness in
people. This new virus was first detected in people in April 2009 in the United States.
Other countries, including Mexico and Canada, have reported people sick with this new
virus. This virus is spreading from person-to-person, probably in much the same way that
regular seasonal influenza viruses spread.
Why is this new H1N1 virus sometimes called “swine flu”?
This virus was originally referred to as “swine flu” because laboratory testing showed
that many of the genes in this new virus were very similar to influenza viruses that
normally occur in pigs in North America. But further study has shown that this new virus
is very different from what normally circulates in North American pigs. It has two genes
from flu viruses that normally circulate in pigs in Europe and Asia and avian genes and
human genes. Scientists call this a “quadruple reassortant” virus.
Do pigs carry this virus and can I catch this virus from a pig?
At this time, there is no evidence that swine in the United States are infected with this
new virus. However, there are flu viruses that commonly cause outbreaks of illness in
pigs. Most of the time, these viruses do not infect people, but influenza viruses can spread
back and forth between pigs and people.
Are there human infections with this H1N1 virus in the U.S.?
Yes. Cases of human infection with this H1N1 influenza virus were first confirmed in the
U.S. in Southern California and near Guadalupe County, Texas. The outbreak intensified
rapidly from that time and more and more states have been reporting cases of illness from
this virus. An updated case count of confirmed novel H1N1 flu infections in the United