Current Trends Update: Influenza Activity -- United States

Beginning in mid-January 1986, school outbreaks of influenza-like illness have been reported from many states. Confirmation of influenza as the etiologic agent for most of these outbreaks is not yet available. School outbreaks of influenza type B in Georgia and Iowa provide examples of the rapid spread of influenza among schoolchildren.

In Georgia, during the week ending January 18, type B virus was isolated from four Atlanta-area students in two influenza-like outbreaks at a college and an elementary school, where absenteeism peaked at 30%. During the week ending January 25, outbreaks of influenza-like illness were reported from schools in all areas of Georgia.

In Iowa, during the week ending January 18, seven type B influenza viruses were isolated from nine students among those with influenza-like illnesses in outbreaks in Marion County. Four type B viruses were isolated from 10 students tested in Webster County, and five type B viruses were isolated from four of 11 students tested and from a teacher in a Madison County school outbreak. During the week ending January 25, school outbreaks of influenza-like illness were reported from all areas of Iowa, with absentee rates in many schools in the 15%-25% range.

Influenza type B virus infections do not appear to be restricted to children and working-aged adults. A nursing-home outbreak has now been confirmed in Connecticut from January 3 to January 20, where 37 (32%) of the 115 residents developed influenza-like illnesses. An earlier nursing-home outbreak has been reported (1).

Tallies of patients with influenza-like illnesses seen by sentinel physicians* nationwide continued at intermediate levels averaging 8.0 for the reporting week ending January 8, 1986, and 7.7 for the reporting week ending January 15.

For the week ending January 25, five states (Delaware, Minnesota, New Jersey, North Carolina, and Virginia) and the District of Columbia reported widespread outbreaks of influenza-like illness, and 13 states (Connecticut, Idaho, Illinois, Iowa, Kansas, Kentucky, Maryland, Michigan, Oklahoma, Oregon, Pennsylvania, Wisconsin, and Utah) reported regional outbreaks. This represents an increase from the preceding week when only Delaware reported widespread outbreaks, and six states reported regional outbreaks.

Arkansas, Connecticut, Iowa, Michigan, Tennessee, Virginia, and the District of Columbia have recently reported their first influenza isolates--all type B--of the season. Thirty-two states and the District of Columbia have now reported influenza virus isolates this season (Figure 2). Twenty-eight states and the District of Columbia have reported type B isolates; 14 have reported type A(H3N2); and one, Hawaii, has reported type A(H1N1).

The percentage of pneumonia and influenza (P&I) deaths reported from the 121 U.S. cities for the week ending January 25 was 6.1%, compared with 6.2% for the preceding week. These are the first weeks that the P&I percentage has reached 6.0% since March 1985. Reported by State and Territorial Epidemiologists; State Laboratory Directors; N Swack, PhD, State Hygienic Laboratory, University of Iowa, Iowa City; J Patterson, JD Smith, E Weir, T Munro, Div of Public Health, Georgia Dept of Human Resources; E Moses, Virus Laboratory, University of Arkansas for Medical Science, Little Rock; N Fithian, B Jones, M Zweig, Dept of Epidemiology and Public Health, Yale University School of Medicine, New Haven, Connecticut; Statistical Svcs Br, Div of Surveillance and Epidemiologic Studies, Div of Field Svcs, Epidemiology Program Office, WHO Collaborating Center for Influenza, Influenza Br, Div of Viral Diseases, Center for Infectious Diseases, CDC.

Reference

1. CDC. Update: influenza activity--United States--and the role of rapid virus typing in improving amantadine use. MMWR 1986;35:46-7. *Cases reported by those members of the American Academy of Family Physicians Research Panel who serve as sentinel physicians for influenza.

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