The answer to typhus is antibiotics, specifically Doxycycline. But the more you use an antibiotic, the more likely the disease will mutate.
There were 167 cases of typhus from January 1, 2018, through February 1 of this year, up from 125 in 2013 and 13 in 2008, according to the California Public Health Department.
https://www.theatlantic.com/health/archive/2019/03/typhus-tuberculosis-medieval-diseases-spreading-homeless/584380/
Mostly homeless people. A growing illness and potentially no more medicine that works = potential plague.