The flu is a contagious, respiratory illness caused by influenza viruses. It can cause mild to severe illness, and at times can lead to death. The best way to prevent seasonal flu is by getting a seasonal flu vaccination each year.
Every year in the United States, on average:
Some people, such as older people, young children, pregnant women and people with certain health conditions such as asthma, diabetes or heart disease are at increased risk for serious complications from seasonal flu illness.
This flu season, scientists believe that a new and very different flu virus (called novel 2009 H1N1) may cause more people to get sick than during a regular flu season. It also may cause more hospital stays and deaths than regular seasonal flu.
Symptoms of seasonal flu include:
Complications of flu can include bacterial pneumonia, ear infections, sinus infections, dehydration and worsening of chronic medical conditions such as congestive heart failure, asthma or diabetes.
Flu viruses are thought to spread mainly from person to person through coughing or sneezing of people with influenza. Sometimes people may become infected by touching something with flu viruses on it and then touching their mouth or nose. Most healthy adults may be able to infect others beginning one day before symptoms develop and up to five to seven days after becoming sick. That means that you may be able to pass on the flu to someone else before you know you are sick, as well as while you are sick.
The best way to prevent seasonal flu is to get a seasonal flu vaccination each year. There are two types of flu vaccines:
About two weeks after vaccination, antibodies develop that protect against influenza virus infection. Flu vaccines will not protect against flu-like illnesses caused by non-influenza viruses.
Yearly seasonal flu vaccination should begin in September, or as soon as the seasonal flu vaccine is available, and continue throughout the flu season into December, January and beyond. This is because the timing and duration of flu seasons vary. While seasonal flu outbreaks can happen as early as October, most of the time seasonal flu activity peaks in January or later.
In general, anyone who wants to reduce their chances of getting seasonal flu can get vaccinated. However, certain people should get vaccinated each year either because they are at high risk of having serious flu-related complications or because they live with or care for high-risk persons. During flu seasons when vaccine supplies are limited or delayed, the Advisory Committee on Immunization Practices makes recommendations regarding priority groups for vaccination.
People who should get a seasonal flu vaccination each year include:
Some people should not be vaccinated without first consulting a physician. They include:
If you have questions about whether you should get a flu vaccine, consult your health-care provider.
-National Institute of Allergy and Infectious Diseases
2009 H1N1 Flu
What is 2009 H1N1?
2009 H1N1 is a new influenza virus causing illness in people. This new virus first was detected in people in the United States in April 2009. This virus is spreading from person-to-person worldwide, in much the same way that regular seasonal influenza viruses spread.
How does 2009 H1N1 virus spread?
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 – such as a surface or object – with flu viruses on it and then touching their mouth or nose.
Can I get 2009 H1N1 more than once?
Getting infected with any influenza virus, including 2009 H1N1, should cause your body to develop immune resistance to that virus so it's not likely that a person would be infected with the identical influenza virus more than once. (However, people with weakened immune systems might not develop full immunity after infection and might be more likely to get infected with the same influenza virus more than once.) However, it's also possible that a person could have a positive test result for flu infection more than once in an influenza season. This can occur for two reasons:
What are the signs and symptoms of this virus?
The symptoms of 2009 H1N1 flu virus include fever, cough, sore throat, runny or stuffy nose, body aches, headache, chills and fatigue. Some people may have vomiting and diarrhea. People may be infected with the flu, including 2009 H1N1, and have respiratory symptoms without a fever. Severe illnesses and deaths have occurred as a result of illness associated with this virus.
How severe is illness associated with 2009 H1N1 flu virus?
Illness with 2009 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.
In seasonal flu, certain people are at "high risk" of serious complications. About 70 percent of people who have been hospitalized with this 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.
Young children are also at high risk of serious complications from 2009 H1N1, just as they are from seasonal flu. And while people 65 and older are the least likely to be infected with 2009 H1N1 flu, if they get sick, they are also at "high risk" of developing serious complications from their illness.
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.
How does 2009 H1N1 flu compare to seasonal flu in terms of its severity and infection rates?
With seasonal flu, we know seasons vary in terms of timing, duration and severity. Seasonal influenza can cause mild to severe illness, and at times can lead to death. Each year, in the United States, on average 36,000 people die from flu-related complications and more than 200,000 people are hospitalized from flu-related causes. Of those hospitalized, 20,000 are children younger than 5 years old. More than 90 percent of deaths and about 60 percent of hospitalization occur in people older than 65.
When the 2009 H1N1 outbreak was first detected in mid-April 2009, CDC began working with states to collect, compile and analyze information regarding the 2009 H1N1 flu outbreak, including the numbers of confirmed and probable cases and the ages of these people. The information analyzed by CDC supports the conclusion that 2009 H1N1 flu has caused greater disease burden in people younger than 25 years of age than older people. At this time, there are relatively fewer cases and deaths reported in people 65 years and older, which is unusual when compared with seasonal flu. However, pregnancy and other previously recognized high-risk medical conditions from seasonal influenza appear to be associated with increased risk of complications from this 2009 H1N1. These underlying conditions include asthma, diabetes, suppressed immune systems, heart disease, kidney disease, neurocognitive and neuromuscular disorders and pregnancy.
How long can an infected person spread this virus to others?
People infected with seasonal and 2009 H1N1 flu shed virus and may be able to infect others from one day before getting sick to five to seven days after. This can be longer in some people, especially children and people with weakened immune systems and in people infected with the new H1N1 virus.
What can I do to protect myself from getting sick?
This season, there is a seasonal flu vaccine to protect against seasonal flu viruses and a 2009 H1N1 vaccine to protect against the 2009 H1N1 influenza virus. A flu vaccine is the first and most important step in protecting against flu infection.
Take these everyday steps to protect your health:
What is the best technique for washing my hands to avoid getting the flu?
Washing your hands often will help protect you from germs. CDC recommends that you wash your hands with soap and warm water for 15 to 20 seconds. When soap and water are not available, alcohol-based disposable hand wipes or gel sanitizers may be used. You can find them in most supermarkets and drugstores. If using gel, rub your hands until the gel is dry.
-Centers for Disease Control