May 1955: First issue of Virology; first English-language journal dedicated to virology

4 May 1984: HTLV-III, later HIV, identified as the cause of AIDS by Robert Gallo and coworkers

5 May 1939: First electron micrographs of tobacco mosaic virus taken by Helmut Ruska and coworkers

5 May 1983: Structure of influenza neuraminidase solved by Jose Varghese, Graeme Laver and Peter Colman

8 May 1980: WHO announced formally the global eradication of smallpox

11 May 1978: SV40 sequenced by Walter Fiers and coworkers

12 May 1972: Gene for bacteriophage MS2 coat protein is sequenced by Walter Fiers and coworkers, the first gene to be completely sequenced

13 May 2011: Boceprevir approved for the treatment of chronic hepatitis C virus (HCV) infection, the first direct-acting antiviral for HCV

14 May 1796: Edward Jenner inoculated James Phipps (pictured) with cowpox

15/16 May 1969: Death of Robert Rayford, the earliest confirmed case of AIDS outside Africa

18 May 1998: First World AIDS Vaccine Day

20 May 1983: Isolation of the retrovirus LAV, later HIV, by Luc Montagnier, Françoise Barré-Sinoussi and coworkers

23 May 2011: Telaprevir approved for the treatment of chronic HCV infection

25 May 2011: WHO declared rinderpest eradicated

31 May 1937: First results in humans from the 17D vaccine for yellow fever published by Max Theiler and Hugh H. Smith