Just wondering over dinner if Perry/other foreigners brought global diseases with them when the country opened up, and couldn’t find an answer. Like how conquistadors brought small pox to North America. If not, what gave the population resistance to the diseases of the last 200 years?
Really thank /u/ParallelPain for salvaging my old comment.
I'll just add a brief comment on the possible (or sometimes assumed) relationship between open-up of ports after Perry and mass outbreak in the end of Tokugawa Shogunate.
It is true that Japan experienced several large-scale outbreaks of different infectious diseases during 1850s and 1860s after the arrival of Perry, and some Japanese are said to have blamed coming foreign ships for a possible source of these outbreaks. According to a famous episode, people of the suburb of Edo (now Tokyo) were reported to witness a strange chimera of tiger - wolf - racoon dog (虎狼狸) (see the linked ukiyoe illustration) or fox fay-beast (Kitsune) with multiple tails that caused the disease, and some of them believed that this beast came from USA (Fujita 2020: 68f.).
The source of the cholera nation-wide outbreak in Japan 1858 indeed came from an U.S. steam frigate Mississippi dropped in Nagasaki on her way from China Sea to USA.
On the other hand, large-scale outbreak of measles also broke out around Edo in 1862 when the 3rd outbreak - 1858 had been the 2nd - of cholera during Tokugawa Shogunate overwhelmed Japan, but we don't know the exact source of this outbreak. Measles had been known in Japan for long.
References:
Please see this answer by /u/y_sengaku.
As for small pox specifically, Japan was never cut off from mainland Eurasia. Small pox arrived in Japan in the 8th century and had ravaged the archipelago ever since until it was eradicated.
