Pathogen migrates north into Alaskan oysters

Gastroenteritis caused by Vibrio parahaemolyticus is normally associated with oysters harvested in warm-water estuaries, not the arctic waters of Alaska. So American scientists were surprised to isolate the pathogen from sick passengers on board cruise ships in Prince William Sound. The scientists, who were investigating a large outbreak of diarrhoea, identified 22 affected passengers from three separate cruises during July 2004. The illness was clearly linked to oysters from a local farm (adjusted odds ratio 5.2; 95% CI 1.47 to 18.54), even though the sick passengers had eaten only one oyster each on average. A media appeal in Alaska identified 52 more people who had become ill soon after eating Alaskan oysters.

Credit: NEW ENGLAND JOURNAL OF MEDICINE

This outbreak occurred 1000 km further north than any previous outbreaks, and the researchers think ocean warming may be partly responsible. On the index farm, water temperatures in summer have risen by a steady 0.2°C a year since 1997. In 2004, water temperatures stayed above 15°C throughout July and August for the first time. Public health authorities will now have to rethink their surveillance strategy for V parahaemolyticus, not least because the contaminated oysters responsible for this outbreak contained 3000 times fewer bacteria than the safe threshold for shellfish set by the US Food and Drug Administration.

N Engl J Med 2005;353: 1463-70

Excess deaths from heart attack remain unexplained

Americans admitted to hospital with a heart attack in December are more likely to die than those admitted at other times of the year. It's unclear why, but some observers suspect the excess deaths have something to do with suboptimal treatment during the winter holiday season, when many hospitals are understaffed. To investigate this possibility, researchers analysed data from a national database of Medicare patients admitted for heart attack between 1994 and 1996.

Patients admitted in December were …