Again and again it happens that humans fall ill with diarrhoea or have to vomit because they have come into contact with virus-contaminated liquids. This happens, for example, in swimming pools, hospitals, during floods or when collecting faeces and urine in dry toilets. Many infectious diseases are transmitted to humans by means of an intermediate reservoir such as water, blood or urine. Even today, several million children die every year from digestive-system diseases and respiratory infections – above all in countries with a weak infrastructure.

But the exact method and in what quantity viruses living in water are absorbed through human skin have until now scarcely been investigated. “In order to model the spread of virus diseases, one must know the probability of infection after one has come into contact with a polluted liquid,” explains Ana Karina Pitol, who is working on her doctorate at Eawag on just this topic.

Risk models identify infection hotspots

Microbiologist Pitol has developed a model based on laboratory experiments that describes exactly this process – how viruses are transmitted to human skin from liquids. The result is partially dependent on the virus concentration in the liquid and how much liquid remains on the skin. In order to get numbers as realistic as possible, Pitol worked with human cadaver skin as well as genuine, infectious viruses. “Normally, one carries out such experiments with model viruses that are not dangerous for humans as well as with synthetic skin,” explains Pitol. But: with this method one gets results that are too inexact, she found in comparative experiments.