A study involving Otago University has found that a number of African people were misdiagnosed with malaria, then treated for it, after being hospitalised with fevers.
More than 800 severely ill patients in Tanzania were analysed to understand how they got a fever.
Professor John Crump of Otago University said the results show that fewer than 2% of those tested did actually have malaria.
He said invasive bacterial infections such as typhoid fever and some infections associated with animals such as leptosporosis were common, but they were not considered nor diagnosed.
Professor Crump said the results of the study have already influenced the way hospitals diagnose and treat fevers in Tanzania.
But, he said, the study signals a need for more research into the causes of fever in the tropics and appropriate treatment.