North America 27 Sep 2026 · Dr Natalya Mathur
ENCLAI ID ENCLAI-2026-0000450-3 · Cite

Chikungunya in the US: 447 cases in the year to September

ENCLAI SURVEILLANCE BRIEFING · 27 SEPTEMBER 2026Chikungunya in the US: 447 cases in theyear to SeptemberChikungunya fever · The US · reported cases18reported cases in the 30 days to 27 September▲ 12% more than the 30 days before (16)16The 30 daysbefore22Same 30 days, ayear earlier44790 days to 27September2402026 so farThree 30-day windows22A year earlier1630 days before18Last 30 daysLargest counts, last 12 monthsBrazil61,135Colombia13,640Argentina12,184Mexico669The US447France20720 countries with a reported count in this windowWhat this briefing shows1Reported cases rose from 16 to 18 between the two latest 30-daywindows, 12% more.2The latest count of 18 is below the 22 reported in the same 30 daysa year earlier.3The US accounts for 0.4% of the chikungunya cases reported toENCLAI worldwide in 2026 and ranks 4 of 17 reporting countries.Read with care: reports to official surveillance, not people and not a rate. A change between30-day windows can come from reporting timing as much as from transmission.Source: official surveillance reports compiled by ENCLAI · data as of 2026-09-27 ·enclai.net/newsVerify every figure against the source data before use; ENCLAI does not guarantee accuracy orcompleteness.
  1. Reported cases rose from 16 to 18 between the two latest 30-day windows, 12% more.
  2. The latest count of 18 is below the 22 reported in the same 30 days a year earlier.
  3. The US accounts for 0.4% of the chikungunya cases reported to ENCLAI worldwide in 2026 and ranks 4 of 17 reporting countries.
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Largest included reported counts (6 of 20 countries) · 2025-09-27 through 2026-09-27 · source-record dates; coverage varies
Brazil61,135
Colombia13,640
Argentina12,184
Mexico669
United States447
France207
Chikungunya fever — United States · reported surveillance count · 2025-09-27 through 2026-09-27 · inclusive source-record dates
Chikungunya fever — United States · reported surveillance count · 2026-08-28 through 2026-09-27 · inclusive source-record dates
Chikungunya fever — United States · reported surveillance count · 2026-07-28 through 2026-08-27 · inclusive source-record dates
Chikungunya fever — United States · reported surveillance count · 2025-08-28 through 2025-09-27 · inclusive source-record dates
Chikungunya fever · combined reported surveillance count · 2025-09-27 through 2026-09-27 · inclusive source-record dates
Chikungunya fever · weekly reported-count series · Weeks starting 2026-06-22 through 2026-09-07
Largest included reported counts (6 of 20 countries) · 2025-09-27 through 2026-09-27 · source-record dates; coverage varies

The full briefing

Full 2026 picture: Chikungunya fever in United States — reported cases by year, monthly records and every briefing for this pair.

The US reported 447 chikungunya cases in the year to 27 September. 18 of them came in the 30 days to 27 September, against 16 in the 30 days before. The same 30 days a year earlier had 22.

Why it matters

The US accounts for 0.4% of the chikungunya cases reported to ENCLAI worldwide so far in 2026. It ranks 4 of 17 reporting countries.

The numbers

PeriodReported cases
Last 30 days (to 27 September)18
The 30 days before that16
Same 30 days a year earlier22
Year to 27 September447
2026 so far (ENCLAI export)240
The card shows chikungunya in the US. It compares the last 30 days with the 30 days before, as reported to ENCLAI.
The card shows chikungunya in the US. It compares the last 30 days with the 30 days before, as reported to ENCLAI.

What the source says

These figures come from official surveillance reports. They count reports, not people. They are not an incidence rate, the rate of new cases in a population. They do not cover the whole population. The reporting periods do not match these dates exactly. Some reports are incomplete or still in progress. Some run past the window. Some reports do not say which date they use: symptom onset, notification, or confirmation.

Caveats

  • A change between two 30-day windows can come from reporting timing as much as from transmission. The source does not say which.

Where to learn more

Chikungunya fever in the US: the 2026 picture · Chikungunya fever worldwide · the US: all diseases · How to read these counts

Retained reporting context

Included reporting countries

Chikungunya fever

88,594

combined reported surveillance count

2025-09-27 through 2026-09-27 · inclusive source-record dates

For Chikungunya fever, the combined reported surveillance count across the 20 countries with positive reported counts in this selection is 88,594. The selection uses source-record dates 2025-09-27 through 2026-09-27, inclusive. This covers only these reporting countries; source periods and completeness vary.

Exact included country membership
CountryReported countSource-record dates
Argentina12,1842025-09-27 through 2026-09-27
Australia832025-09-27 through 2026-09-27
Bulgaria12025-09-27 through 2026-09-27
Brazil61,1352025-09-27 through 2026-09-27
Colombia13,6402025-09-27 through 2026-09-27
Germany82025-09-27 through 2026-09-27
Finland172025-09-27 through 2026-09-27
France2072025-09-27 through 2026-09-27
United Kingdom152025-09-27 through 2026-09-27
Hong Kong612025-09-27 through 2026-09-27
Italy282025-09-27 through 2026-09-27
Madagascar292025-09-27 through 2026-09-27
Mexico6692025-09-27 through 2026-09-27
Philippines262025-09-27 through 2026-09-27
Poland112025-09-27 through 2026-09-27
Puerto Rico12025-09-27 through 2026-09-27
Singapore22025-09-27 through 2026-09-27
Taiwan292025-09-27 through 2026-09-27
United States4472025-09-27 through 2026-09-27
U.S. Virgin Islands12025-09-27 through 2026-09-27

Snapshot 2026-09-27

Weekly reporting history

Chikungunya fever

weekly reported-count series

Weeks starting 2026-06-22 through 2026-09-07

A retained retrospective weekly reported-count series across included reporting countries. Country membership and reporting completeness can vary by week. Missing weeks remain gaps. This is a separate report-series measure; it does not establish exact incidence or laboratory confirmation.

Retained weekly report series
WeekReported count
2026-06-22 through 2026-06-28218
2026-06-29 through 2026-07-0596
2026-07-06 through 2026-07-122
2026-07-13 through 2026-07-192
2026-07-20 through 2026-07-263
2026-07-27 through 2026-08-026
2026-08-03 through 2026-08-090
2026-08-10 through 2026-08-167
2026-08-17 through 2026-08-2311
2026-08-24 through 2026-08-305
2026-08-31 through 2026-09-066
2026-09-07 through 2026-09-131

Snapshot 2026-09-26

Sources and limitations

  • Window. Each quantity keeps its recorded source-selection dates and coverage notes. Dated batches and weekly or genomic observations retain their separate measures. Publication or capture dates do not establish case onset, equal cohorts or period completeness.
  • Denominator. The retained counts do not establish complete populations, equal reporting cohorts or incidence rates. Source period bounds and definitions can differ.
  • Case definition. Case definitions are set nationally and change over time. Counts for the same disease in different countries may not be counting the same thing.
  • Revisions. Agencies restate figures. Values here are as reported at the time of publication; see the update history below.

ENCLAI counts reflect verified records available from reporting sources for the stated window. They are not estimates of total incidence and should not be interpreted as medical advice. Full methodology: the dataset.

Review and corrections

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