This decrease is attributed to the introduction of new antiviral drug combinations. The spread of the AIDS epidemic, particularly into rural areas, has resulted in coinfections with different infectious agents, producing a variety of novel pathologies. Several subtypes of HIV, as well as novel recombinations, have been reported. The incidence of hepatitis B is declining as a result of vaccination, while that of hepatitis C is increasing. A high prevalence of hepatitis D exists in some regions of the Amazon, where in conjunction with hepatitis B, it is believed to be the principal cause of Labrea black fever.
Influenza is a major concern.
The vast forests that still cover large areas of Brazil are home to many known and unknown viruses. The Evandro Chagas Institute in Belem alone has isolated more than 183 new arboviruses. Among new viruses causing fatal infections recently discovered in Brazil are Rocio virus, which causes encephalitis, and Sabi virus, which causes hemorrhagic fever. Several cases of hantavirus infection have also been reported, but on these and other occasions, the lack of a biosafety level 4 laboratory in the country impeded further work. Bacterial Diseases Enteric bacterial infections are an important cause of illness in Brazil.