U.S. health officials are investigating the mysterious case of a person in Utah who contracted Zika while caring for an elderly man infected with the virus who died last month.

 One major hurdle is thwarting efforts to measure the extent of the Zika epidemic and its suspected links to thousands of birth defects in Brazil: accurate diagnosis of a virus that still confounds blood tests.

 The world's first malaria vaccine has cleared one of the final hurdles prior to being approved for use in Africa.

 Tweaking the brain's immune system with a drug has prevented mice developing dementia, a study shows.

 HIV is evolving to become less deadly and less infectious, according to a major scientific study.

US researchers have revealed another baby carrying the HIV virus, which leads to Aids, may have been cured through early treatment.