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Current Trends Update: Influenza Activity -- United States

Since January 1, 1985, the number of reporting states with laboratory isolates of type A(H3N2) influenza virus has increased rapidly. On January 1, the total was eight states; on January 8, 13 states; and on January 15, 22 states (Figure 3). In addition to the previous report of a nursing-home outbreak in New York City (1), nursing-home outbreaks have now been reported in California and Pennsylvania. In Pennsylvania, four influenza virus isolates were recovered from elderly patients in an outbreak that affected about 40 (19%) of 210 nursing-home residents in early January in Crawford County. In California, 23 (46%) of the 50 residents of a nursing home in Santa Clara County had influenza-like illnesses in an outbreak in late December and early January. Reported by B DeArmond, MD, Santa Clara County Health Dept, California Dept of Health Svcs; J Schivers, MD, Regional Clinical Laboratories of Northwest Pennsylvania, Erie, B Kleger, PhD, Pennsylvania Dept of Health; State and Territorial Epidemiologists and State Laboratory Directors; Influenza Br, Div of Viral Diseases, Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: Reports of this year's influenza outbreaks indicate that persons of all ages are being infected with type A(H3N2) strains (1). The current information is consistent with past observations that, when outbreaks occur in nursing homes, high attack rates can occur. Although information about the vaccination status of the affected nursing-home residents has not been reported, previous studies, particularly during the A/Bangkok/1/79(H3N2) outbreaks in 1982-1983, showed that use of influenza vaccine greatly reduced the complications from influenza. Because the present type A(H3N2) strains now causing outbreaks are similar to the A/Philippines/2/82 component of the current vaccine, it is likely that similar protection will be conferred. Persons providing medical care to those at high risk of acquiring severe influenza should continue to offer influenza vaccine to those who have not yet received it. Under circumstances where influenza A virus is already active within the community, amantadine hydrochloride is recommended to provide protection for the first 2 weeks after vaccine administration, as well as to control outbreaks when they occur (2). Because renal function often decreases with age, a reduced dosage of 100 mg/day is generally advisable for persons aged 65 years and older to minimize the risk of toxicity (2,3). Amantadine treatment, begun within the first 1 or 2 days of illness, may also assist in the recovery process for persons with influenza A infection.


  1. CDC. Update: influenza activity--United States. MMWR 1985;34:6, 11.

  2. ACIP. Prevention and control of influenza. MMWR 1984;33:253-60, 265-6.

  3. Committee on Immunization, Council of Medical Societies, American College of Physicians. Guide for adult immunization. 1st ed. Philadelphia: American College of Physicians, 1985.

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