Born in
Finland (then part of Sweden), Orreus was trained at
Åbo and relocated to Russia in 1755. He continued medical training in Moscow and is believed to have taken part in the
Seven Years' War. On August 2, 1768
Catherine II of Russia awarded him the
Doctor of Medicine diploma, the first of its kind ever issued in Russia. However the plague infiltrated mainland Russia, causing the
epidemic of 1770–72 that peaked in Moscow in September and October 1771. Orreus was summoned to Moscow by
Grigory Orlov, the statesman placed in charge of emergency anti-plague action. Orlov and Orreus arrived in the city September 26, 1771, at the peak of the outbreak. Orreus was assigned to manage
quarantine hospitals in Moscow. At first, he opposed
Afanasy Shafonsky and denied the plague nature of the Moscow epidemic, but despite bitter medical dispute the course of events persuaded Orreus to admit the facts. He summarized his experience during the plague in a 1784 treatise
Descriptio pestis, quae anno 1770 in Jassia et 1771 in Moscua grassata est (
A Description of Plague that Ravaged Iaşi in 1770 and Moscow in 1771). In 1776 Orreus retired from state service and settled on his estate near
Saint Petersburg. His experiments with agricultural novelties were publicized in the
Proceeds of the Free Economic Society. He also authored
A Brief Essay on Fever, Diarrhea and Bloody Flux and other Diseases Prevalent among Soldiers, printed in the Russian language at Saint Petersburg in 1808. ==References==