# Screw-worm fly outbreaks in Mexico

> Live situation record from CLSTR: https://clstr.news/situations/screw-worm-fly-outbreaks-in-mexico
> Updated: 2026-09-05T19:38:05.000Z. Sources: 7. Developments: 2.

Screw-worm fly (Cochliomyia hominivorax) outbreaks have caused significant agricultural and public health challenges across Mexico. In Chihuahua, the infestation expanded to 30 municipalities, primarily affecting livestock including bovine, equine, and canine species. Nationally, epidemiological reports identified 478 confirmed cases of human myiasis during 2025 and 2026.

In Querétaro, health authorities confirmed seven human cases in 2026, including one death in the municipality of Querétaro. In response to the spread, officials have activated epidemiological surveillance and sanitary response protocols, including continuous monitoring and investigation across medical units to prevent further transmission.

## Claims

- The Querétaro State Health Secretariat confirmed a new case of human myiasis caused by the screw-worm in a 69-year-old woman. (corroborated by 3 sources)
- The state has accumulated seven confirmed cases of human myiasis during 2026. (corroborated by 3 sources)
- One death due to human myiasis has been recorded in the municipality of Querétaro. (corroborated by 3 sources)
- The seven cases are distributed as follows: one in Amealco de Bonfil, two in Cadereyta de Montes, three in Querétaro, and one in San Juan del Río. (corroborated by 3 sources)
- Myiasis is an infestation caused by the larvae of the fly Cochliomyia hominivorax, commonly known as the cattle screw-worm. (corroborated by 3 sources)
- The state health authorities activated epidemiological surveillance and sanitary response protocols. (corroborated by 2 sources)

## Timeline

### 2026-09-05: Querétaro reports seven cases of human myiasis in 2026

Querétaro health authorities confirmed a seventh case of human myiasis caused by the screw-worm in 2026, following a new infection in a 69-year-old woman. One death has also been recorded in the state.

7 sources. https://clstr.news/cluster/quertaro-reports-seven-cases-of-human-myiasis-in-2026

### 2026-08-15: Screw-worm fly outbreaks affect multiple Mexican states

Screw-worm fly outbreaks are spreading in Mexico, affecting 30 municipalities in Chihuahua primarily in livestock and 56 municipalities in Veracruz regarding human myiasis cases.

5 sources. https://clstr.news/cluster/screw-worm-fly-outbreaks-affect-multiple-mexican-states

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Cite as: Screw-worm fly outbreaks in Mexico. CLSTR, https://clstr.news/situations/screw-worm-fly-outbreaks-in-mexico