The flu is a respiratory illness caused by infection with the influenza virus. The virus is spread from person-to-person through contact with contaminated respiratory droplets (i.e., coughing and sneezing). Symptoms appear abruptly about one to four days later. Patients may experience fever, chills, headache, tiredness, muscle aches and pains, cough, sore throat, nasal congestion and/or runny nose.
There are several strains of the virus. Most serious cases of human infection are caused by strains of influenza A and influenza B. Flu season occurs during the winter months, usually starting in November and running through March, with peak incidence in December, January, and February. In otherwise healthy people, symptoms usually go away within a week or two. However, in the elderly, people with weak immune systems, or those with underlying disease, influenza can lead to serious complications, such as pneumonia, bronchitis, sinus infections, or exacerbation of underlying illness.
In an average year, the flu causes 114,000 hospitalizations and 20,000 deaths. In severe, global outbreaks, the number of deaths can be exceedingly high. According to the National Foundation for Infectious Diseases, an outbreak of influenza A in 1918, caused 500,000 deaths in the U.S. and 20 million worldwide. A 1968 outbreak caused more than 50,000 deaths in the U.S. Those over 65 account for more than 90 percent of deaths from the flu.
Preventing the Flu
One of the most important ways to prevent the flu is with a flu shot. The vaccine may also prevent complications of infection. Since different strains of the flu tend to circulate every year, a flu shot must be given annually. The vaccine is composed of three strains of the flu virus that are most likely to circulate in a given year. This year, the flu shot will contain two strains of type A and one of type B: A/Moscow/10/99 (H3N2)-like, A/New Caledonia/20/99 (H1N1)-like, and B/Hong Kong/330/2001-like strains.
It takes a few weeks for the body to build up enough immunity after the shot. So the vaccine is best given before the start of flu season – usually during October and November. People who are at highest risk of developing severe illness or complications from the flu should get the vaccine in October. That includes those 65 and older, children six months to 23 months, patients with a chronic medical condition, and women who will be more than three months pregnant during flu season. Health care workers and household contacts or caregivers of those who are at high risk for the flu complications should also get a flu shot in October. Flu shots are also recommended for healthy people 50 to 64 (many in this group have at least one underlying medical problem that could be exacerbated by the flu) and anyone who wants to avoid getting the flu. However, experts recommend the last two groups wait until November to get their shots to ensure vaccine availability for those who need it most. A flu shot is not advised for people who are allergic to eggs (the vaccine is grown in an egg culture) or other components of the vaccine, people who had a previous reaction to a flu shot, and those with a potentially paralyzing neurological condition, called Guillain-Barre syndrome. Anyone with a current illness and fever should postpone a flu shot until the symptoms are gone.
Predicting Flu Risk
A flu vaccine is an important component in the fight against the flu. But unfortunately, it doesn't provide a 100 percent guarantee against infection. A person can be infected with a strain of the virus not included in the vaccine. And even when exposure occurs to one of the vaccine strains, those with weak immune systems, such as the elderly, may still be susceptible to illness. Researchers at Eastern Virginia Medical School are working on a test that may help predict whether a person is at risk for contracting the flu – even after immunization with the vaccine. In the current study, investigators are looking at two groups of older individuals - healthy patients and those with congestive heart failure. Blood samples are drawn before and after an injection with the flu vaccine. Each blood sample is placed in a culture dish with a live flu virus. Blood contains both red cells and white cells (the cells that fight infection). The researchers will examine and compare the reactions of the cells in the blood samples to the flu virus before and after vaccination. Hopefully, the blood test will show how well an individual's immune system responds to the flu virus. That information may lead to the ability to identify patients or groups of patients who are most at risk of getting the flu, even after immunization. Doctors can then take extra steps to reduce the risk of infection, such as giving antiviral medication during outbreaks or peak flu season.
If you have any questions of concerns about your need for a flu shot, talk with your family health care provider.
For general information on influenza and the flu vaccine: Centers for Disease Control and Prevention, www.cdc.gov
National Foundation for Infectious Diseases, www.nfid.org