Rain and bigger storms could be the cause of more stomach bugs in certain countries, according to new research.
Torrential rain leads drains to overflow, releasing germ and virus riddled water into waterways and if this water is swallowed while engaging in watersports for example, it can make people sick.
According to research, it is more likely to be viruses that cause people to be ill rather than the germs.
The research was carried out as part of a project called Viroclime which aims to improve tools for tracking harmful viruses from human sewage in European waters.
It looked at viruses from five European sites including Spain, Hungary, Sweden, and Greece and one site in Brazil.
There are two types of virus which could act as a signal to more serious water-based diseases - one belongs to the winter vomiting bug family, the other to noroviruses.
"If we had better data, which EU project Viroclime can gather, and we analyse the data using a health risk-based approach, we could get better estimated disease burdens from recreational water exposures," Mark Sobsey, a virologist from the University of North Carolina, said.
However, he added that testing water for viruses is still difficult and costly.
Scientists believe that being able to monitor viruses in water could help them predict the effects of climate change and to develop new health protection measures to suit such change.
It could also help predict a rise in the number of stomach illnesses by exploiting the link to rainfall.