Investigation following disease in triathletes is now completed
8 October 2010
Illness was probably caused by seawater swallowed during the swimming competition of the triathlon
Many participants in the first Danish Ironman-distance triathlon, The Challenge Copenhagen Triathlon, held in Copenhagen on 15 August, reported that they had become ill with diarrhea and abdominal pain after the competition.
The day before the competition, Copenhagen was hit by strong torrential rain, which meant that swimming bans were issued several places in the area around Copenhagen the next day. Therefore, there was also speculation in the media as to weather the triathlon participants could have become ill from swimming in the sea the morning after the heavy rains.
Questionnaire from the Statens Serum Institut
In collaboration with the triathlon organizers the Statens Serum Institut launched a survey among the participants. The aim was to find out if there had been an actual disease outbreak and, if so, to try to identify the etiology and investigate if seawater was the likely source of infection.
Preliminary results of the survey questionnaire
Statens Serum Institut has now completed the questionnaire investigation and although data analysis has not yet been concluded it is never-the-less possible to answer some of the key questions.
Among those who completed the entire course, more than half, 778 participants, completed the questionnaire. Fifty-five percent stated they became ill shortly after the competition and among these, 70 percent reported to have had diarrhea.
It is well-known that some people may experience stomach problems as a direct result of the extremely physical exertion the body is exposed to, in an Ironman competition and in the questionnaire 20 percent of the participants stated that they thought, their symptoms might be due to exhaustion.
A large proportion of those who reported being sick, however, had prolonged symptoms, and the average duration of diarrhea was four days.
Seawater has probably led to illness
Participants were also asked if they thought, they had swallowed seawater during the swimming competition. There was a clear correlation between having swallowed seawater and the risk of becoming ill.
There was however no correlation between disease and various kinds of food and snacks that was served or distributed before and during the competition.
Results of laboratory analysis
A number of participants had a stool sample submitted for microbiological analysis after the competition, in either Denmark or in a laboratory in their home country (about half of the participants in the contest does not live in Denmark).
Several participants were found to have an infection with either campylobacter or a special diarrhea-causing E. coli bacteria (ETEC). Campylobacter is the most common pathogenic intestinal bacteria in Denmark and is usually transmitted through food, but sometimes also with drinking water.
However, in the majority of examined stool samples no disease-causing microorganisms were found. It is also noteworthy that many participants stated they got sick already on the day of the competition, which is otherwise not typical for bacterial and viral infections that give gastrointestinal illness.
Provisional conclusion of the survey
The survey has shown that there was in fact a large outbreak of gastrointestinal illness after the Ironman-distance competition held in Copenhagen August 15th 2010.
Furthermore, the questionnaire results show, that it was probably seawater swallowed during the swimming competition that caused disease.
Some participants have become ill from bacterial infections, but there has probably also been toxins or other substances in the seawater, causing gastrointestinal symptoms after a short incubation period and also the hard physical exertion may in some participants have contributed to the symptoms.