Flu seasons usually begin in October and peak between December and February. In Tennessee in 2022–23, flu began in late September, and by November children were being hospitalized at rates close to the peaks of high-severity seasons. In November 2022, the state health department, CDC and Vanderbilt University Medical Center investigated what was happening across 14 of Tennessee's 95 counties in middle Tennessee.
Early and intense
Flu hospitalizations among people under 18 in Tennessee, 2022–23 against 2019–20 — the recent season with the highest peak for this age group — with the medium, high and very high thresholds. CDC.
- Hospitalizations: weekly rates reached 12.6 per 100,000 children under 5 and 6.9 per 100,000 people under 18 — above the high-intensity threshold and approaching very high.
- Emergency visits: in the week ending November 26, flu-like illness accounted for 31% of emergency department visits by people under 18 (past seasons' peaks: 14%–34%). For all ages it reached 15%, above every past peak (5%–13%).
Who was testing positive
Among 4,626 people tested at participating clinics during November 4–18:
| Children | Adults | |
|---|---|---|
| Tested | 2,164 (47%) | 2,462 |
| Positive | 33% | 20% |
| Had this season's flu vaccine | 23% | 34% |
| Given antivirals, if positive within 48 hours of symptoms | 41% | 55% |
Of 332 sequenced viruses, 179 (54%) were A(H3N2) and 153 (46%) A(H1N1)pdm09 — all genetically similar to the vaccine's components. Vaccination was low, not mismatched.
Spread at home
A follow-up survey reached 185 people with flu and their 480 household contacts. 151 (31%) of the contacts fell ill, 83 of them with symptoms of influenza-like illness.
| Contacts | Ill | Adjusted odds of illness |
|---|---|---|
| Under 18 | 76 of 170 (45%) | 2.5 times adults' (95% CI 1.6–4.0) |
| 18 and over | 75 of 310 (24%) | reference |
| Vaccinated | 48 of 174 (28%) | 1.0 (0.6–1.6) against unvaccinated |
| Unvaccinated | 103 of 306 (34%) | reference |
After adjusting for household size and vaccination, the secondary attack rate was 11.9% among child contacts and 5.1% among adults.
Limits
- The sample came from middle Tennessee over two weeks, and only 11% of those invited completed the survey.
- Tennessee does not require reporting to its immunization registry, so vaccination may be undercounted.
- The household model assumes every ill contact had flu, though other respiratory viruses were circulating.
What to do
Everyone 6 months and older should get a flu vaccine every season, avoid contact with people who are ill, and take antivirals when a clinician recommends them — prioritized for hospitalized patients, children under 2 and people with underlying conditions.
Sources
Based on Thomas CM, White EB, Kojima N, et al. "Early and Increased Influenza Activity Among Children — Tennessee, 2022–23 Influenza Season." MMWR; a work of the United States government in the public domain. The report gives the odds ratio for sharing a bedroom with an ill person as 2.11 with a 95% confidence interval of 2.59–2.80, which cannot contain its own estimate; that figure is left out here. The report's promotional graphic is not reproduced.
Licence: CC0 1.0 (public domain) · Adapted from www.cdc.gov
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