Some of Brazil's most isolated communities are helping scientists unravel the genetics of malaria and anaemia.
Child health was tested
Both are significant killers in Acre - Brazil's most westerly province, which is 90% rainforest.
Researchers from the University of Sao Paulo have made the long journey to assess the health of children in two towns.
The project is the subject of the BBC World Service programme Health Matters, to be broadcast this week.
Dr Marcelo Urbano Ferreria is leading the research in Asis Brasil, a traditional Amazonian town mainly home to rubber-tappers and their families, and Acrelandia, a more modern town set up in the 1970s to service the logging industry.
The population of Brazil has its origins in a wide variety of different races - immigrants from Europe and Africa mixing with indigenous peoples.
The researchers ultimately believe that understanding the complex genetic background of these children could help improve treatments for common diseases.
Their large-scale health screening programme will find those most at risk from anaemia, and hopefully enable their diets to be improved.
Dr Ferreria said: "The purpose is not just to quantify the health problems but also to identify causes.
"For example anaemia is prevalent, but the causes seem to be changing, not just access to food rich in iron, but also changes in dietary patterns."
Jose Sebastian Bocalo Rodriz, the Mayor of Acrelandia, told Health Matters that children in the town faced many health problems.
He said: "In the urban area it's children's diseases such as diarrhoea and respiratory infections.
"The healthcare system is improving, but it's still not enough. We need more health professionals, though it's much better than in other local areas."
Acrelandia now has two health clinics - a vast improvement from the days when serious illness meant a seven-hour drive to the state capital.
The results of the study suggest that one in five children in the town are malnourished, while 35% of them are anaemic, and quarter have intestinal parasites, despite mothers being given anti-worm drugs to give to their children.
Dr Ferreira said: "Based on these results we will try to suggest some interventions, to be carried out through local health services, not just providing drugs but also advice on nutrition."