The COVID-19 pandemic led to worldwide handwashing, masking, social distancing, and lockdowns. Although this was designed to prevent the spread of COVID-19, it affected many other viruses as well, essentially preventing the 2020-2021 flu season. It may have even eradicated a strain of flu: wild influenza B/Yamagata has not been definitively seen anywhere in the world since April 2020.

However, there have been sporadic cases of influenza B/Yamagata as recently as October 2022; it's unknown whether these are wild or vaccine derived.

In 1980, the World Health Organization (WHO) declared smallpox eradicated. At present, this is the only infectious disease to be eradicated in humans (an animal disease, rinderpest, was declared eradicated in 2011). Typically, the WHO waits some number of years without seeing a wild case to declare a disease eradicated -- the last known smallpox case was in 1977 (3 years prior to announcing it was eradicated); for rinderpest, it was 2003 (8 years).

The WHO has also declared two strains of wild polio to be eradicated, most recently in 2019. (Note that vaccine-derived cases of these strains of polio continue to circulate.)