A Deadly, Spreading Migration; Global warming brings new diseases up North.

Byline: William Underhill

The Danish angler never saw his killer. Earlier this summer the 62-year-old (whose name was never released by Danish authorities) was fishing with a friend in the Baltic Sea when a microscopic marine bug entered his system, probably through a cut or scrape. Within a week he was dead, one arm already amputated. His attacker: Vibrio vulnificus, a flesh-eating bacterium that normally makes its home in the warmer waters of the Gulf of Mexico. Although the bug is not always fatal, it can be especially dangerous to the old or the weakened.

Was this a freak accident caused by a rogue organism? Maybe not. Some scientists argue that last summer's soaring temperatures are part of a warming trend that is encouraging a slew of heat-loving organisms to extend their habitats into the once chillier North. Recent tests in Germany showed that Vibrio vulnificus was present in more than nine out of 10 samples of Baltic Sea water. "Microorganisms aren't clever," says Tove Roenne, a doctor with Denmark's National Board of Health. "They just do whatever the temperature tells them to do."

Plenty of victims can testify to the consequences. The authorities on the Italian Riviera were forced to close beaches this summer after more than 100 holidaymakers were hospitalized following exposure to Ostreopsis ovata , tropical algae that can cause rashes and diarrhea. Farm animals, too, have suffered. Cattle herds in Northern Europe this summer came down with the region's first cases of potentially fatal Blue Tongue disease, a midge-borne ailment previously associated only with the Mediterranean region.

The link between global warming and the spread of warmth-loving diseases is not ironclad. Blue Tongue disease might have found its way north through a zoo animal. And this isn't the first time that Vibrio vulnificus has surfaced in the Baltic. Infections were reported during the ...