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A 23-meter-long sailboat set off last week from Argentina for Antarctica’s Weddell Sea with eight scientists, lots of cloacal swabs, and a genetic fingerprinting machine aboard.

His spinal fluid was sent to a state laboratory that performs genetic fingerprinting on bacteria samples, where researchers later found Roberson had tested positive for listeria.

The cases were linked through genetic fingerprinting, which indicates they likely have a common source of infection.

"It's easy to say whether something's there or not with genetic fingerprinting," explained Newcastle University's Prof David Graham, who is involved in the development of that test.

Disease detectives searching for clues to human-created disease outbreaks seek smoking guns such as a genetic fingerprinting link of laboratory samples to samples obtained from diseased patients.