Adapted from information available from the Center for Disease Control (CDC)

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 and countries have been reporting cases of illness from this virus. As of 10 May 2009, there were 4400 cases reported in 29 countries. In the United States, there were 2254 cases in 44 states. By our observation, these numbers have increased exponentially from last week.

Is this new H1N1 virus contagious?
CDC has determined that this new H1N1 virus is contagious and is spreading from human to human. However, at this time, it is not known how easily the virus spreads between people. Typically, flu viruses spread through ‘droplet nuclei’. This means that any secretions from the respiratory system, whether visible or invisible, can transmit the virus.

What are the signs and symptoms of this virus in people?
The symptoms of this new influenza A H1N1 virus in people are similar to the symptoms of regular human flu and include fever, cough, sore throat, body aches, headache, chills and fatigue. A significant number of people who have been infected with this virus also have reported diarrhea and vomiting. Also, like seasonal flu, severe illnesses and death has occurred as a result of illness associated with this virus.

How severe is illness associated with this new H1N1 virus?
It’s not known at this time how severe this virus will be in the general population. CDC is studying the medical histories of people who have been infected with this virus to determine whether some people may be at greater risk from infection, serious illness or hospitalization from the virus. In seasonal flu, there are certain people that are at higher risk of serious flu-related complications. This includes young children, pregnant women, people with chronic medical conditions and people 65 and older. It’s unknown at this time whether certain groups of people are at greater risk of serious flu-related complications from infection with this new virus. CDC also is conducting laboratory studies to see if certain people might have natural immunity to this virus, depending on their age.