Influenza surveillance

Influenza Season of 1999-2000: Closure and Summary

The Oregon State Public Health Laboratory (OSPHL) is pleased to announce the beginning of its annual inter-season moratorium on complimentary rule/out influenza specimen testing. We can anticipate suspension of this hiatus some time next autumn. Watch for the announcement of the opening date for the 2000-2001 season in the CD Summary.

The 1999–2000 season was a curious one. It got off to a record early start, with the first documented case reported by staff of the Providence Portland Medical Center Infectious Disease Laboratory. The culture-confirmed patient was a resident of Clackamas County with onset in mid-October. This was (seasonally speaking) the earliest documented influenza case in modern Oregon history (last two decades of the second millennium). And this was no fluke: four other cases were reported with onsets by the first week of November. Cases peaked by onset during week one of 2000 with the last reported case occurring in mid-March.

After that, however, things kind of wandered off course for what some feared would be a bad year. In all, only 30 isolates were confirmed during the extended season by the OSPHL, ranking 13th among the previous 20 seasons (range 0-180). The 530 specimens submitted to OSPHL was slightly above the mean of 510 and ranked 7th (range 118-860). The recovery rate of 5.7% ranked 19th (range 4%-32%). All of the 1999–2000 isolates were type A. Of the nine that have been subtyped, eight were H3N2; one was H1N1.

Reports of culture-confirmed or antigen-positive patients as well as inpatients with a diagnosis of influenza-like illness were also received from staff of the Providence Portland Medical Center Infectious Disease Laboratory and from clinical epidemiologists of Legacy Portland Hospitals. Forty-six patients had culture-confirmed type A influenza and 36 others were suspected of having influenza. Receipt of these voluntary case reports enhanced assessment of influenza activity in Oregon.

Lab surveillance is critical in establishing the viral strains in circulation, with attendant implications for prophylaxis, treatment and vaccine preparation. While this season is history, lab and epidemiological services are always available for unseasonal cases or clusters of influenza-like illness. Don't hesitate to call 503-731-4024.

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