Scanning EM of Influenza Virus From: http://www.cdc.gov/ncidod/diseases/flu/fluvirus.htm

This year’s influenza season promises to be a bit more challenging than last. Ongoing efforts locally and nationally to increase vaccination rates, especially in high-risk populations, have met with success. While the success has been somewhat mixed, overall vaccination rates have increased steadily over the last decade. According to a report issued by the Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices, vaccination rates among elderly patients increased from 33% in 1989 to 63% in 1997. The vaccination rate for patients under age 65 at high risk for morbidity and mortality from influenza was less than 30% in 1997. Because of widespread manufacturing difficulties, the supply of influenza vaccine will be late in arriving and limited in its availability this year. It is likely that there will be a significant shortfall in vaccine supplies. Prioritizing utilization will be even more important this year than ever before.

Here are the highlights of the September 1^st PCHI Focus on the topic:

1. Prioritize Vaccine
    Administer vaccine first to people at high risk of complications from influenza. They include everyone 65 years of age and older and younger people with underlying medical conditions.

• Delay any flu shot campaigns until November
• In November, vaccinate high-risk patients, people who are 65 and older, immunocompromised, or have certain chronic conditions. Also vaccinate healthcare workers who might spread the flu to these high-risk patients.
• In December, give flu shots to unvaccinated healthcare workers and household members of high-risk patients.
• After December, give vaccine to healthy people age 50 and older and others who want to be vaccinated.

While vaccination is the most effective method of reducing the incidence of influenza, there are now 4 antiviral drugs with demonstrated efficacy in treatment. Two antivirals, amantadine and rimantadine, are both approved for use for prophylaxis.

Chemoprophylaxis:

The Drug Therapy Committee recommends the use of rimantadine (100mg orally twice daily) for unvaccinated patients with household or occupational contact. Rimantadine may be administered for up to 21 days for prophylaxis.

• 70-90% effective
• Although CNS side effects are seen, they are rare (1-3%)
• Given the limited data available for Relenza and Tamiflu for prophylaxis, the Drug Therapy Committee does not recommend them as first-line drugs. Use of Relenza and Tamiflu should be reserved for patients known to be intolerant of rimantadine or those with documented exposure to Influenza B infection.
• Doses should be reduced for patients with renal or hepatic dysfunction

Treatment:

The Drug Therapy Committee recommends the use of rimantadine (100mg orally twice daily for 5 days) for the treatment of influenza.

• Treatment can be expected to reduce the duration of illness by about 1 day
• Therapy must be started within 48 hours of the onset of symptoms
• Because of the difficulty in differentiating influenza from other viral illness, the use of the rapid antigen test is recommended prior to initiating antiviral therapy.
• Because of the limited data available for use of Relenza and Tamiflu in high-risk populations, side effects, ease of administration (Relenza by inhalation), and cost, the Drug Therapy Committee does not recommend them as first-line drugs. Use of Relenza and Tamiflu should be reserved for patients with known to be intolerant of rimantadine or those with documented Influenza B infection.

Selected References

1. Prevention and control of influenza. Recommendations of the Advisory Committee on Immunization Practices. MMWR 2000; 49(RR03);1-38 (http://www.cdc.gov/mmwr/preview/mmwrhtml/rr4903a1.htm)
2. Keyser L, Karl M, Nafziger A, Bertino J. Comparison of central nervous system adverse effects of amantadine and rimantadine used as sequential prophylaxis of influenza A in elderly nursing home patients. Arch Intern Med 2000;160(10):1485-1488.
3. Hayden F, Atmar R, Schilling M et al. Use of the selective oral neuraminidase inhibitor oseltamivir to prevent influenza. N Engl J Med 1999;341(18):1336-1343.

What you should know about the flu

Information for patients about influenza prevention and treatment

"The flu" is an infection of the respiratory tract caused by the influenza virus. Although it generally gets better on its own, the flu can cause severe illness in some people. It usually starts fairly suddenly with a fever, cough, sore throat, runny or stuffy nose, as well as headache, muscle aches, and often, extreme fatigue. Nausea, vomiting, and diarrhea are sometimes seen as well, especially in children. Most people who get the flu recover completely in 1 to 2 weeks. Unfortunately, some people can develop serious and potentially life-threatening medical complications, such as pneumonia.

The flu virus lives in the respiratory tract of infected persons and is spread when others come in contact with droplets carried in the air. These droplets are produced when a person with the flu sneezes or coughs. Avoiding or limiting contact with ill persons and frequently washing your hands can reduce, but will not eliminate, the risk of infection. Anyone who is coughing or sneezing should cover his or her nose and mouth with a handkerchief to limit spread of the virus. Your best protection from the flu is being vaccinated. The vaccine used is produced each year and is based on predictions made about which strain of virus will cause infections this year. Unfortunately, the production of vaccine this year has been very difficult. As a result, the vaccine will be late in arriving to your physician’s or nurse’s office. Even when your physician or nurse receives the vaccine, there may not be enough for everyone. Because of this shortage, it will be very important to administer the vaccine to people at very high risk for developing serious illness if they get the flu. The Centers for Disease Control and Prevention suggest the elderly and those with certain medical conditions should get vaccinated first. Your doctor or nurse will advise you if you fall into one of these groups.

If you do not receive a "flu shot", there are drugs available that can reduce your risk of coming down with the flu. There are 2 antiviral drugs (amantadine and rimantadine) that your doctor can prescribe in the event that you come into close contact with someone with the flu. The Drug Therapy Committee of the Massachusetts General Hospital recommends rimantadine (also known as Flumadine). Rimantadine is taken by mouth once or twice a day for as long as 21 days. It is between 70 and 90% effective in preventing the flu.

If you come down with the flu, there are 4 antiviral drugs (amantadine, rimantadine, Relenza and Tamuflu) which can be used to limit its duration. All work about the same, reducing the length of time of symptoms by about 1 day. The Drug Therapy Committee recommends the use of rimantadine for treatment of influenza as well. It is important that you start taking rimantadine and the other antiviral drugs within 2 days of feeling sick. Rimantadine and the other antivirals do not work for other kinds of viral illness. Your doctor or nurse may want to do a test to see if you have the flu first. This test involves swabbing the inside of your nose and may take a day for the results to be known. Bedrest, drinking plenty of fluids and taking acetaminophen (Tylenol and others) for fever and aches and pains are also appropriate.

The Massachusetts General Hospital is providing a toll-free number you can call to find out when the flu shots will be available. If you are coming to the Hospital for a flu shot, you should call 1-877-733-3737 to make certain that the vaccine has arrived and you are eligible to receive it.