Brazilian purpuric fever (BPF) is an illness of children caused by the bacterium Haemophilus influenzae biogroup aegyptius which is ultimately fatal due to sepsis. BPF was first recognized in the São Paulo state of Brazil in 1984. At this time, young children between the ages of 3 months and 10 years were contracting a strange illness which was characterized by high fever and purpuric lesions on the body. These cases were all fatal, and originally thought to be due to meningitis. It was not until the autopsies were conducted that the cause of these deaths was confirmed to be infection by H. influenzae aegyptius. Although BPF was thought to be confined to Brazil, other cases occurred in Australia and the United States during 1984–1990.
Haemophilus species are non-spore-forming gram-negative coccobacilli . They lack motility and are aerobic or facultatively anaerobic. They require preformed growth factors that are present in blood, specifically hemin (X factor) and NAD or NADP (V factor). The bacterium grows best at 35–37 °C and has an optimal pH of 7.6. Haemophilus species are obligate parasites and are part of the normal flora of the human upper respiratory tract.