Influenza update 2000.

Between 30,000-40,000 Americans die annually as a result of influenza epidemics. Spread primarily through the respiratory tract, influenza's classic signs and symptoms are the abrupt onset of fever, myalgia, headache, sore throat, malaise, and nonproductive cough. The elderly and patients with underlying medical illnesses may be at risk for secondary complications. Influenza is caused by an RNA myxovirus that exists in types A, B, and C; however, the A and B types are responsible for most human illness. The Centers for Disease Control and Prevention tracks the viruses' regular pathway through the US each year as they emerge first in Alaska and spread through the lower 48 states, peaking in activity during the winter months. Influenza is preventable by vaccination (efficacy 70%, depending on individual immune status) and is recommended for everyone at increased risk of complications from influenza between 6 months and 50 years of age, and universally for those over the age of 50. The composition of the vaccine has been changed for 2000-2001 to include two new type-A strains and one new type-B. Currently four drugs are available for the treatment of influenza. Early diagnosis can help reduce the inappropriate use of antibiotics and provide the option of using antiviral therapy. Bacterial infections can have similar symptoms or be complications of influenza and should be suspected and treated appropriately if present.