Arbovirus studies in nupeko forest, a possible natural focus of yellow fever virus in Nigeria I. Description of the area and serological survey of humans and other vertebrate hosts

Studies were conducted in a restricted area of gallery forest along the middle upper Niger River, Nigeria. Yellow fever neutralizing antibodies were found in 25% of the human population and in 57% of the monkeys tested. Both the abundance of monkeys and the ecological conditions in such forest appear to be favourable for year-round maintenance of yellow fever virus.