Influenza surveillance during winter 1997-1998 in Israel

Tamar Peled, Michael Weingarten, Noemi Varsano, Andre Matalon, Adi Fuchs, Robert D. Hoffman, Charna Zeltcer, Ernesto Kahan, Ella Mendelson, Tiberio A. Swartz

Research output: Contribution to journalArticlepeer-review

Abstract

Background: Each winter influenza activity is a major cause of morbidity and mortality both in Israel and worldwide. Objectives: To identify the influenza viruses active in Israel during the winter season and to assess the extent of influenza morbidity. Methods: Information was collected on a population of 18,684 individuals enrolled in two community clinics in central Israel. It included the total number of visits for acute respiratory infection - including influenza and influenza-like illness (ARI/flu-like) - during a 20 week surveillance period (23 November 1997 to 27 March 1998) and the percent of influenza virus isolates in nasopharyngeal specimens from a sample of patients with ARI/flu-like collected on a weekly basis during the same period. Results: A total of 5,947 visits for ARI/flu-like were recorded among 18,684 enrolled patients in two community clinics (18.1%). The progressive increase in the number of visits for ARI/flu-like reached a peak on week 2/98 with 597 visits and a rate of 31.95 visits per 1,000 population. After this, a decrease to the initial values was evident by week 12/98. Most affected patients were in the age groups 5-14 and 65 years and over, with a rate of 733.5 and 605.3 visits per 1,000 population, respectively. Influenza virus was isolated from 92 of the 426 nasopharyngeal specimens (21.6%). The most commonly detected strain was A/Sydney/5/97(H3N2) like (77.2%). The peak rate of isolates was recorded at the beginning of January (01/98). Conclusions: A/Sydney/5/97(H3N2) like-strain was the dominant influenza, virus. Its presence did not prevent the simultaneous activity of influenza A/H1N1 virus. The dynamic of the clinical disease as expressed by the weekly visit rate for ARI/flu-like was similar to the temporal pattern of the virological findings. The extent of morbidity suggests moderate epidemic activity.

Original languageEnglish
Pages (from-to)911-914
Number of pages4
JournalIsrael Medical Association Journal
Volume3
Issue number12
StatePublished - 2001
Externally publishedYes

Keywords

  • Community survey
  • Influenza
  • Surveillance
  • Virology

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