Diseases such as typhus, smallpox, typhoid, malaria, tuberculosis and STDs seem to be nonexistent during the 19th and 20th century in Russia. It seems the bigger issues were social and political upheavals, famine, and the increase use of alcohol and tobacco. Why is this case? Countries such as England during the Industrial Revolution and pre-war era were dealing with massive public health problems that lead to plague, typhus and smallpox. In the United States, polio was also a large issue. Is the climate of Russia an explanation?
There are a few issues that factored into the fortunes of Muscovy in avoiding many of the major plagues that affected the rest of the world. Climate indeed was certainly a factor, in that it is more difficult for infectious diseases to spread in such a northern location. But also factoring into it was the much lower population density of Muscovy. Few large cities existed, and those that did were separated by large distances that discouraged travel except along the great North-South River systems. East-west travel, on the other hand, was entirely overland and difficult even during prime traveling periods.
The difficulty of east-west travel goes in hand with the deep seated xenophobia present in Muscovite society. Travel outside of the forested zone was practically non existent for Muscovites, and few Europeans came to Muscovy. That is not to say trade did not exist, but it was certainly not the commerce that was maturing in Western and Central Europe.
And so that leaves North-South transmission, which was certainly an issue of concern for the tsar and his court. Fortunetly Muscovy already possessed an extensive line of fortifications along its southern border (an effort to stop, slow, or at least provide warning against the regular Tatar raids that emanated from the Crimea/Ukrainian steppe) which provided a handy tool for preventing the spread of disease too. As Boeck (one of my personal favorite historians) points out, these fortifications, along with other aspects of Muscovite society, display some of the earliest prototypes of modern borders, complete with border guards and passports. Voivodas (governors) of fortress-towns like Voronezh, Ryazan, and Tula were regularly instructed to stop foreigners and inspect them for signs of plague, and to quarantine them if necessary.
So to summarize, Medieval Russia and Russia in its later evolutions was (and to some extents still is) a society that is particuarly well endowed in dealing with infectious disease, through both its isolation and early developed sense of borders.
For more I recommend: Boeck, Brian J. “Containment vs. Colonization: Muscovite approaches to settling the steppe” in Peopling the Russian Periphery. Edited by Nicholas Breyfogle et al. Routledge Chapman & Hall, 2009.