From Illuminati-Manga:

What do two Japanese detectives, a naked man on a city street, and a roundworm from Botswana all have in common? In the first volume of Manhole, Ken Mizoguchi and Nao Inoue investigate a string of bloody and mysterious murders, but their work uncovers a deadly biological agent which poses a threat of epidemic proportions. An unlikely lead starts them in the pursuit of a mysterious self-titled photographer, but meanwhile the infections keep spreading. The series may be best described as the thrilling combination of a detective story with biological horror.