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Infectious Diseases

Influenza Season is Here

Fighting the Flu

Tissue boxEvery winter, millions of people will suffer from influenza, a highly contagious infection - more commonly known as the flu. Caused by a virus (germ) that infects the nose, throat, and lungs, "the flu bug" is spread from person to person mostly by the coughing and sneezing of infected persons. The period before symptoms start ranges from 1-4 days, with an average of 2 days.

Adults typically are infectious from the day before symptoms begin and can remain infectious as much as 5 days after illness starts. Children can spread viruses for around 10 days. Severely immunocompromised persons can shed virus for much longer periods of time.

Preventive Medicine

To reduce your risk of influenza, follow these simple steps:

However, your best line of defense for remaining healthy during the flu season is a yearly flu vaccine. Vaccination can reduce your chance of contracting influenza, minimize your symptoms if infection does occur following the vaccine, and help prevent the spread of the infection to others.

Find the Flu Shot in Your Area

Types of Vaccines

Influenza viruses often change, making it hard to predict which strain will strike in a given year. In the spring of each year, health officials around the world work with laboratories to predict which one of the many different strains of influenza viruses will be circulating the following flu season. During this time, a new flu vaccine is developed to include 3 major current strains, including 2 A strains and 1 B strain. Influenza A and B are the two types of influenza viruses that cause epidemic human disease, also known as seasonal influenza. This vaccine is inactivated and cannot itself cause infection.

With a scheduled appointment, you can receive a flu shot at your doctor's office. Mild side-effects, including a headache or low-grade fever, may occur for a day following the vaccination. (Flu Clinic Locator)

FluMist is a new nasal spray flu vaccine that was licensed in 2003. Unlike flu shots, which are made from killed viruses, the nasal vaccine is made from live, but weakened viruses. Because of this, FluMist is advised only for healthy people aged 5 to 49. Persons in older age groups or those with immune system defects should receive the traditional inactivated vaccine.

Is it too late to get a flu vaccination?

In September, the flu shot (inactivated influenza vaccine) is offered to people at high risk. October through November is the best time to get vaccinated as flu activity typically starts in December. In the United States flu activity generally peaks between late December and early March. After November there is still benefit from getting the vaccine even if flu is present in your community.

Vaccine should continue to be offered to unvaccinated people throughout the flu season as long as vaccine is still available. Once you get vaccinated, your body makes protective antibodies in about two weeks. Because of the dwindling supplies of flu shots, the CDC recommends those with greatest need and highest risk be given the vaccination first.

Who Should Get Vaccinated?

The Centers for Disease Control and Prevention (CDC) in Atlanta cautions that the following people are at high risk of becoming seriously ill from influenza and should be vaccinated each year:

1. People at high risk for complications from the flu, including:

2. People who live with or care for those at high risk for complications from flu, including:

Who Should Not Be Vaccinated?

People with a severe allergy to eggs SHOULD NOT get the flu shot. Developed in medical labs, the viruses used in flu vaccines are grown in eggs. People who are allergic to eggs may experience a serious reaction to the vaccine.

People with asthma should avoid the nasal mist vaccine, and those who have developed an allergic reaction to previous vaccinations should avoid either vaccine type - shot or mist.

Influenza or a Bad Cold?Sick in Bed

While many symptoms of influenza and colds are similar, influenza comes on suddenly, resulting in increasing weakness. Influenza is NOT stomach flu. Fatigue and a dry cough caused by influenza can last for weeks.

Influenza's Symptoms

Can't tell if it is a cold or the flu? Visit the National Institute of Allergy and Infectious Diseases flu fact sheet.

Children and the Flu

Sick ChildBecause an estimated 92 children ages 5 and younger die of influenza annually in the United States, it is important to recognize and treat symptoms in children quickly. Children and adolescents with a fever should not be given aspirin. Tips for Treating the Flu may help your child feel better in the meantime.

In addition to the symptoms of influenza listed for adults, children at times can have middle ear infection (otitis media), nausea, and vomiting. There are lots of viruses that cause respiratory illnesses, so you can't tell by symptoms alone if you have influenza or some other virus.

Seeking Medical Help

Emergency Warning Signs (Informational purposes only)

In children, some emergency warning signs that need urgent medical attention include:

In adults, some emergency warning signs that need urgent medical attention include:

Seek medical care immediately, either by calling your doctor or going to an emergency room, if you or someone you know is experiencing any of the signs described above or other unusually severe symptoms. When you arrive, notify the receptionist or nurse about your symptoms.

For the most current information about Influenza:

What You Should Know About the Flu (CDC)

Influenza (the Flu): Questions & Answers (CDC)

Influenza Symptoms, Protection, and What to Do If You Get Sick (CDC)

Key Facts about Influenza and the Influenza Vaccine (CDC)

Find the Flu Shot in Your Area (www.Flu.gov) 

Focus on the Flu (National Institute of Allergy and Infectious Diseases)

Flu Information (US Food and Drug Administration)

Get Ready for Flu Blog (American Public Health Association)

National Immunization Information Hotline
1-800-232-2522

Flu?Get the Shot (National Institute on Aging)
1-800-222-2225

For more information:

Go to the Infectious Diseases health topic, where you can:

This article is a NetWellness exclusive.

Last Reviewed: Feb 20, 2007

Kurt B Stevenson, MD, MPH Kurt B Stevenson, MD, MPH
Professor of Infectious Diseases
College of Medicine
The Ohio State University