Third plague pandemic

The conventional emergence of the Third Plague Pandemic in Yunnan

The pandemic usually given a birth year of 1855 has plague records in Yunnan reaching back to 1772 — and it did not reach the world for another four decades.

A date with no outbreak attached

No securely documented single outbreak began on a known day in 1855. The conventional date marks a mid-nineteenth-century phase in which plague intensified and became endemic across parts of southwestern China.

Historical research places recognisable plague in Yunnan much earlier: local cases were recorded from the late eighteenth century, with one medical review citing Dali in 1772.

What was moving in Yunnan in the mid-1850s

Military conflict and the increased movement of troops, provisions and refugees in Yunnan during the mid-1850s likely amplified regional transmission.

The escalating Hui Muslim rebellion — later known as the Panthay Rebellion — contributed to that population movement, though its own starting date also varies by account.

There was no single verified ignition: long-standing plague foci interacted with Qing-era economic expansion, trade routes, environmental conditions and wartime movement to produce a sustained regional upsurge.

The global phase came in 1894

Plague did not become a worldwide pandemic in 1855. Its major global dissemination began after it reached Canton and Hong Kong in 1894, and it spread gradually through southern China over the intervening decades.

Carol Benedict traces the Yunnan epidemic to the late eighteenth century; other researchers describe an upsurge at the end of the 1850s or endemicity during the 1850s and 1860s. Some scientific studies date the third-pandemic lineage or transmission process to 1772, while historians reserve "pandemic" for the global phase from 1894.

Historical Yunnan sources used changing disease terms, so retrospective identification of individual early outbreaks as bubonic plague requires caution.

Sources

Researched 23 Aug 2026 7 sources 2 audit passes Date disputed

How this was checked

Researched from the web into a fact sheet, rewritten from that sheet, then audited against it by a different model. How the pipeline works →

Date disputed. Sources disagree; the research places it at ~1855.

What the sources leave uncertain

“1855” is a conventional periodization, not a well-attested day or necessarily the first Yunnan outbreak.
Carol Benedict traces the Yunnan epidemic to the late eighteenth century; other researchers describe an upsurge at the end of the 1850s or endemicity during the 1850s–1860s.
Some scientific studies date the third-pandemic lineage or transmission process to 1772, while historians reserve “pandemic” for the global phase beginning in 1894.
Historical Yunnan sources used changing disease terms, so retrospective identification of individual early outbreaks as bubonic plague requires caution.