PORT JACKSON — A modeling study published July 9 in the journal Nature Human Behaviour concludes the 1789 smallpox outbreak in Australia was brought by the British “First Fleet” in 1788. The research challenges long-standing historical theories regarding the origins of the disease that devastated Indigenous populations shortly after European arrival.

The study rejects the hypothesis that the outbreak originated through contact with Indonesian islanders fishing in northern Australia. Instead, the analysis points to the British expedition as the vector for the virus that spread through Indigenous communities.

Modeling of the outbreak in Indigenous communities near Port Jackson indicated the outbreak originated there. This geographic focus aligns with the initial settlement activities of the British colonizers rather than distant northern coastal interactions.

Computer modeling indicated that a smallpox outbreak originating on the north coast could not have spread to Southeast Australia due to thousands of miles of uninhabited desert separating the regions. The physical barriers rendered the northern transmission theory geographically implausible according to the study's simulations.

There were no recorded cases of smallpox on the First Fleet during the voyage. The absence of active infections among the crew and convicts during the transit has led researchers to investigate other mechanisms of transmission.

The likely source of the outbreak were vials of dried smallpox scabs that British medics kept for inoculations. These medical supplies were part of the standard equipment carried by the fleet's medical personnel.

Inoculation was a precursor to smallpox vaccines, which Edward Jenner invented in the 1790s. The practice involved introducing material from smallpox sores to induce immunity, a method that carried risks of causing the disease if not managed correctly.

The study indicates that vials of smallpox scabs may have been replenished when the fleet stopped at Cape Town, South Africa, or Rio de Janeiro, Brazil. These stops provided opportunities for the medical stores to be refreshed before the final leg of the journey.

The Fleet traveled for eight months from Portsmouth, England, to Botany Bay. The British “First Fleet” consisted of 11 ships: two naval vessels, six convict transports, and three ships for provisions.

The Fleet initially landed at Botany Bay but moved to Sydney Cove in Port Jackson due to poor land and water conditions. This relocation placed the settlement in the area where the modeling suggests the outbreak began.

“There is very strong evidence that it was the First Fleet,” said Matthew Cody Nitschke, an expert in computer modeling at Flinders University in Adelaide and a co-author of the study. Nitschke helped develop the computational models that tracked the potential spread of the virus.

“The idea that it came from the North and arrived at exactly the time [as the First Fleet] was always improbable,” said Henry Reynolds, a historian. Reynolds supported the findings by noting the temporal coincidence of the fleet's arrival and the outbreak.

The study estimates approximately 220,000 Indigenous people died from the 1789 smallpox outbreak. This figure shows the catastrophic demographic impact of the disease on the native population.

Alan Williams is an archaeologist at the private firm EMM Consulting and a co-author of the study. Williams contributed archaeological context to the interdisciplinary research team.

The Fleet is 11 ships that left Great Britain to found the penal colony that became the first European settlement in Australia. The study provides a new explanation for how smallpox entered the continent, attributing it to medical practices of the British medics rather than external contact with northern neighbors.

Australia is located in East Asia & Pacific and is classified by the World Bank as a high income economy. The findings revise the historical understanding of the disease's introduction, suggesting that the tools intended for medical protection may have inadvertently caused a widespread epidemic among Indigenous communities.