Graduates and senior students from the Hong Kong College of Medicine (founded in 1887) were employed as assistants to the Government Bacteriologist between 1902 and 1912 to examine rats collected from different parts of the City of Victoria throughout the year for plague infection as part of the surveillance program for plague. In 1907, 23 out of 19500 rats collected from April to September were found to be infected with the plague bacillus. Later, rats were also examined for fleas Xenopsyllax cheopis pulex irritans, the species that carry the plague bacillus.
Note the lack of protective devices (gloves, masks, goggles, and gowns) on the assistants from poor awareness of the potential danger of infection at that time.