Diarrhoea is the leading cause of death in the world with 2.2 million deaths every year. The majority of deaths are among children in developing countries, but the travellers encounter the disease as well. The studies on the aetiology have suffered from serious methodological deficiencies and the results are even controversial. At the same time, the current diagnostic methods are inadequate. The investigators have recently developed novel multiplex RT-PCR methods to cover the majority of diarrhoeal pathogens. The present study is a collaboration between Finland and Sweden/Guinea-Bissau. The aim is to characterize the causative agents of diarrhoea (a) in Finnish volunteers before and after a travel to tropical areas and, (b) in inhabitants of endemic areas in Guinea-Bissau. For these purposes stool samples will be collected from volunteers of different age groups and from healthy volunteers as well as those with diarrhea both in Guinea-Bissau and in Finland. In addition to pathogens, other intestinal microbes and antimicrobial resistance will be investigated

Inclusion Criteria:

1. Accepting to participate and willing to deliver 2 stool samples.
2. With diarrhea: the first 10 children and 10 adults presenting each month at the health facility Without diarrhea: In Bissau matched controls drawn from the registration system at Bandim Health Project. In Finland controls selected at the health facilities participating.

Exclusion Criteria:

• Not willing or able to deliver the stool samples

1. children and adults with diarrhea reporting to Bandim Health Centre
2. age and sex mached children and adults without diarrhea from Bandim
3. children and adults with a recent travel history and suffering from diarrhea reporting to Postitalo Travel Clinic
4. children and adults without diarrhea and no recent travel history reporting to Postitalo Travel Clinic