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What the flu is

The H1N1 influenza virus was first detected in people in the United States in April 2009. It is spreading from person-to-person worldwide, probably in much the same way that regular seasonal influenza viruses spread. On June 11, 2009, the World Health Organization signaled that a pandemic of 2009 H1N1 flu was under way.

Illness with the new H1N1 virus has ranged from mild to severe. While most people who have been sick have recovered without needing medical treatment, hospitalizations and deaths from infection with this virus have occurred.

About 70 percent of people who have been hospitalized with the 2009 H1N1 virus have had one or more medical conditions previously recognized as placing people at high risk of serious seasonal flu-related complications. This includes pregnancy, diabetes, heart disease, asthma and kidney disease.

Although it was originally called "Swine Flu," further study has shown that the H1N1 virus is very different from what normally circulates in North American pigs.

More info about H1N1 from CDC

Who gets the flu

Anyone can get the flu (even healthy people) and anyone can have serious problems from the flu. Students, faculty and staff should be encouraged to talk with their health care providers to determine if they are at higher risk for flu complications, especially if they have been in close contact with others who are sick with flu or flu-like illness.

Some groups are at higher risk for complications from the flu. These include children younger than 5 years of age, pregnant women, people of any age with chronic health conditions (such as asthma, diabetes, or heart disease) and people 65 years of age and older.

Typical flu season

Influenza can cause mild to severe illness, and at times can lead to death. Every year in the United States, on average, 5 percent to 20 percent of the population gets the flu, more than 200,000 people are hospitalized from flu complications and about 36,000 people die from flu-related causes. Most people who get sick from flu recover after about a week. Those who have serious complications or die usually have a pre-existing chronic disease or other factors that make them more vulnerable.

The difference between seasonal and H1N1 flu

There are two kinds of influenza causing concerns this year: seasonal flu and the newer H1N1 flu. Although the symptoms of both types of flu are similar, there are some important differences.

Seasonal flu

Seasonal flu is one of a number of influenza viruses that occur globally each year, usually peaking during the late fall and winter. Vaccine for seasonal flu is created annually based on predictions of which three versions of the virus are most likely to occur. Vaccine is currently available in a variety of medical and community locations.

With seasonal flu, certain people are at higher risk of serious complications if they get the flu. This includes people 65 years and older, children younger than 5 years old, pregnant women and people of any age with certain chronic medical conditions.

H1N1 flu

Early data on H1N1 illnesses suggest that young adults 18 to 24 are getting H1N1 in higher numbers than are older adults.

Adults older than 64 years do not yet appear to be at increased risk of 2009 H1N1-related complications. CDC laboratory studies have shown that no children and very few adults younger than 60 years old have existing antibody to 2009 H1N1 flu virus; however, about one-third of adults older than 60 may have antibodies against this virus. It is unknown how much, if any, protection may be afforded against 2009 H1N1 flu by any existing antibody.

High-risk groups

Children younger than 5
Children and adolescents (younger than 18) who are receiving long-term aspirin therapy and who might be at risk for experiencing Reye's syndrome after flu infection
Pregnant women
Children and adults who have asthma, other chronic pulmonary, cardiovascular, hepatic, hematological, neurologic, neuromuscular or metabolic disorders such as diabetes
Children and adults with suppressed immune systems

How flu spreads

Spread of 2009 H1N1 virus is thought to occur in the same way that seasonal flu spreads. Flu viruses are spread mainly from person to person through coughing or sneezing by people with influenza. Sometimes people may become infected by touching something with flu viruses on it and then touching their mouth or nose.

People infected with seasonal and 2009 H1N1 flu may be able to infect others one day before getting sick and up to five to seven days after. This can be longer in some people, especially children and people with weakened immune systems.