Visitors to the World Athletics Championships in Finland have had to brave wind and rain, and officials say they now face the possibility of catching the world's first mobile phone virus.
Officials in Finland, home to the world's largest mobile phone maker, Nokia, said there had been outbreaks of the Cabir virus at Helsinki's Olympic Stadium.
Jarmo Koski, a security official at telecoms firm TeliaSonera, said: "At most we are speaking about dozens of infections but during a short period and in one spot this is a huge number."
Cabir, first reported in June last year, uses Bluetooth to jump between mobile phones.
That means it can spread over distances of up to 10m, which in a packed stadium could include dozens of phones.
The recipient needs to accept a download to be infected and, while telecoms security officials say the risk of catching a mobile virus is small, thousands of phones have already been hit around the world.
Antti Vihavainen, head of the mobile unit at antivirus software firm F-Secure, said: "There must be a lot of infected phones at the stadium and a lot of Bluetooth traffic."
It is the early version of Cabir, which can infect only one phone at a time. Later versions of Cabir are much more fierce," he added.
Since it was invented, the virus has so far spread to more than 20 countries, from the US to Japan and from Finland to South Africa.
F-Secure said there are 55 viruses or other malicious programs spreading between mobile phones and other mobile devices.
Cabir drains the power of the infected phone as it tries to replicate itself on nearby mobiles but the most damaging viruses could disable a phone, requiring a factory reset.
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