Antiviral Drugs & The Flu

By the Center for Disease Control
October 7, 2004

Three antiviral drugs (amantadine, rimantadine, and oseltamivir)are approved and commercially available for use in preventingflu.All of these medications are prescription drugs, and adoctor should be consulted before the drugs are used. Whenused for prevention, they are about 70% to 90% effectivefor preventing illness in healthy adults.

Four antiviral drugs (amantadine, rimantadine, zanamavirand oseltamivir) have been approved for treatment of theflu. If taken within 2 days of getting sick, these drugscan reduce the symptoms of the flu and shorten the time youare sick by 1 or 2 days. They also can make you less contagiousto others. All of these drugs must be prescribed by a doctorand taken for 5 days. Antiviral drugs are effective onlyagainst influenza viruses. They will not help the symptomsassociated with the common cold or many other flu-like illnessescaused by viruses that circulate in the winter.

All of the antiviral drugs are different in terms of whocan take them, how they are given, any dosing changes basedon age or medical conditions, and sideeffects. Your doctorswill help decide whether you should get antivirals and whichone you should get.

Use of Antiviral Drugs

Antiviral drugs are most often used to control flu outbreaksin institutions, for example in nursing homes, or in hospitalwards, where people at high risk (see below) for complicationsfrom flu are in close contact with each other. Antiviralsalso have been used on cruise ships or similar settingsto control outbreaks of the flu.

In the event of an outbreak, public health practice is tocombine the use of flu vaccine and antivirals. In a nursinghome during an outbreak, for example, residents and staffare given the flu vaccine and antivirals to prevent flu untilthe vaccine takes effect (about 2 weeks). This practice continuesas long as influenza is occurring in that setting.

Doctors also can prescribe antivirals for flu to peoplenot living in institutional settings, but treatment mustbegin within 2 days of the onset of symptoms for it to beeffective. Also, while all antivirals lessen the symptomsof illness and shorten the duration of illness, only 1 (oseltamivir)has been shown in a study to reduce some complications requiringantibiotics.

When considering antivirals, it’s important to rememberthat most healthy people recover from the flu without complications.

Antiviral Drugs for People at High Risk for Complications

Some people are considered to be at high risk from complicationsof flu. This includes

Note that none of the antivirals are approved for use inchildren less than 1 year of age.

*Children 6-23 months of age are at increased risk for influenza-relatedhospitalization.

Who Should Get Antiviral Drugs

For Treatment:If you get sick with flu-like symptoms this season, yourdoctor first may give you a test to find out whether youhave influenza. (Symptoms of flu include: fever (usuallyhigh), headache, tiredness, a sore throat and dry cough,nasal congestion, and body aches.) Your doctor also willconsider a number of things before making a treatment decision,such as your risk for complications from flu.

For Prevention: In the event of a flu outbreakin a home, institution, or community, your doctor may chooseto give antivirals to you as a preventive measure, especiallyif you are at high risk for complications from the flu. Also,if you are in close contact with someone who is consideredat high risk for complications from flu, you may be givenantiviral drugs to prevent passing flu to the high-risk person.

Antiviral Drugs: Summary of Side Effects - Amantadinean d Rimantadine

Among some healthy adults and children, side effects can includecentral nervous system (CNS) side effects such as nervousness,anxiety, difficulty concentrating, and lightheadedness,and gastrointestinal side effects like nausea and lossof appetite. CNS side effects happen more often among personstaking amantadine than among persons taking rimantadine.Among some other persons with long-term illnesses, moreserious side effects, such as delirium, hallucinations,agitation, and seizures, can occur. Side effects usuallydiminish and disappear after 1 week.

Zanamivir

This drug is inhaled and can cause side effects, especiallyin those with asthma or other chronic lung disease. Decreasedrespiratory function and bronchospasm have been reportedwith use of zanamivir. Zanamivir is generally not recommendedfor use in persons with underlying lung disease such as asthmaand chronic obstructive pulmonary disease. Other side effectsreported by less than 5% of those who have used this drugare diarrhea, nausea, sinusitis, nasal infections, bronchitis,cough, headache, and dizziness.

Oseltamivir

The side effects reported most often in those people who tookthis drug were gastrointestinal (i.e., nausea and vomiting).Nausea and vomiting may be less severe if oseltamivir is takenwith food.
Click on the link below for more detailed information aboutantiviral drugs for influenza:
Prevention and Control of Influenza, Recommendations of theAdvisory Committee on Immunization Practices (ACIP) Morbidityand Mortality Weekly Report (MMWR), April 25, 2003 / Vol.52 / No. RR-08.

Click on the link below for more detailed information about antiviral drugs for influenza:
Prevention and Control of Influenza, Recommendations of the Advisory Committee on Immunization Practices (ACIP) Morbidity and Mortality Weekly Report (MMWR), April 25, 2003 / Vol. 52 / No. RR-08.

Antiviral Drug Links

U.S. Food and Drug Administration (FDA) website, antiviral drugs for influenza pages:

Antiviral Information

Resources

Influenza Information by Telephone and U.S. Mail
If you do not have access to the Internet, you may call the toll-free number 888-CDC-FACTS (888-232-3228). Once the system has answered, you may bypass other disease information not specific to influenza by pressing options 2, then 2, then 1, then 3, then 4, then 3, and then 3. At the prompt that asks if you want a current copy of the ACIP recommendations, please leave your name and address, and the document will be mailed to you.

*Note: This link leads outside the CDC site to another federal agency or CDC partner site. Any links from these sites to nonfederal organizations' links do not constitute an endorsement of these organizations or their programs by CDC or the federal government, and none should be inferred. CDC is not responsible for the content of the individual organization Web pages found at these links. The link will open the page in a new browser window.

Questions & Answers: Breastfeedingand the Flu

January 12, 2004

What precautions should I take to protect my babyif I have the flu and am breastfeeding?

Nursing mothers who have the flu should take thefollowing steps before every breastfeeding and when handlingtheir infants:

•  Put on a surgical mask. (You can purchase surgicalmasks in most drugstores.)

•  Wash your hands thoroughly, and dry them witha clean towel or paper towels. (Information about hand hygienecan be found at: www.cdc.gov/od/oc/media
/pressrel/fs021025.htm.)

•  Leave your breasts covered until you have puton a surgical mask and washed your hands. You can then beginbreastfeeding.

•  Do not remove your surgical mask until youare done breastfeeding and you have put your baby down.

How long should I continue to take theseprecautions?

Continue to take these precautions atevery feeding for 7 days following the first dayof your illness (when you first noticed flu symptoms).

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More than 200 different viruses are known to cause the common cold.

Influenza virus is responsible for acute upper respiratory disease, usually accompanied by fever and myalgia. Virions are usually roughly spherical and about 200nm in diameter. The envelope contains rigid "spikes" of haemagglutinin and neuraminidase which form a characteristic halo of projections around negatively stained virus particles. Flu virus photos - University of Cape Town

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