直近の過小評価に注意

米国：外来受診者中のILI患者の割合
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Information on outpatient visits to health care providers for
influenza-like illness (ILI) is collected through the U.S. Outpatient
Influenza-like Illness Surveillance Network (ILINet). ILINet
consists of outpatient healthcare providers in all 50 states,
Puerto Rico, the District of Columbia and the U.S. Virgin Islands.
Approximately 85 million patient visits were reported during the
2020-21 season. Each week, approximately 3,000 outpatient
healthcare providers around the country report to CDC the
number of patient visits for ILI by age group (0-4 years, 5-24
years, 25-49 years, 50-64 years, and ≥65 years) and the total
number of visits for any reason. A subset of providers also
reports total visits by age group. For this system, ILI is defined
as fever (temperature of 100°F [37.8°C] or greater) and a cough
and/or a sore throat. The case definition no longer includes
“without a known cause other than influenza”. Sites with
electronic health records use an equivalent definition as
determined by public health authorities. Since ILINet monitors
visits for ILI and not laboratory-confirmed influenza, it will
capture visits due to any respiratory pathogen that presents with
ILI symptoms. These data should be evaluated in the context of
other surveillance data to obtain a complete and accurate
picture of influenza virus activity.

Nationwide during week 5, 1.7% of patient visits reported through ILINet were due to respiratory illness that included fever plus a
cough or sore throat, also referred to as ILI. This percentage is below the national baseline. One of the 10 HHS regions (Region 7) is
above its region-specific baseline, and the remaining regions are below their baselines. Multiple respiratory viruses are co-circulating,
and the relative contribution of influenza virus infection to ILI varies by location.

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https://www.cdc.gov/flu/weekly/index.htm

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