Epidemiology
Reported cases of B virus infection in humans are rare. There have been around 50 reported cases of human infection since the virus was first identified in 1932; among these cases, 21 have been fatal.[5]
The majority of infections have originated from the bite or scratch from an infected macaque monkey, from a percutaneous injury contaminated by macaque body fluids (e.g., via needlestick or cut in the laboratory or veterinary setting), or from infected body fluid or materials entering broken skin. There has also been at least one published report of fatal B virus infection resulting from a splash to intact mucosa without associated injury.[3]
In the US, a large number of non-human primates are kept as pets despite strong opposition to the importation of exotic animals by a number of US organisations, including the Department of Agriculture and Centers for Disease Control and Prevention (CDC).[6] Pet macaque bites inflicted on people visiting a pet macaque owner or inflicted by pet macaques that have escaped confinement are occasionally reported to the CDC. There have been at least four published reports of children bitten by macaques; a 2-year-old boy bitten by a bonnet macaque kept by a neighbour as a pet; a 7-year-old girl bitten while trying to feed a macaque in a park; a 4-year-old boy bitten in a zoo; and a 10-year-old girl bitten whilst on holiday in Bali, Indonesia.[6][7][8] One small study revealed that 4 of 6 pet macaques involved in biting humans were seropositive for B virus; the owners of the remaining 2 macaques refused requests for testing.[9] Analysis of the history of these macaque encounters with adults and children revealed that 4 of 9 (44%) children were bitten compared with only 3 of 12 (25%) adults.
Bites from macaques who roam freely in temples, parks, and other settings in southern Asia (most notably Indonesia, Nepal, and India) are periodically reported to the CDC and B Virus Research and Resource Laboratory (BVRRL), and there has been at least one reported case of a macaque bite in a temple in Bali.[10] Two studies of temple macaques in Indonesia and Nepal showed that 64% and 82% of temple macaques, respectively, were infected with B virus.[11][12]
Only one case of human-to-human transmission has been documented; the case, which was reported in a study of a B virus outbreak involving 4 people in Florida, resulted from direct physical contact with lesions.[13] Among the four people, three were animal handlers (two suffered bite wounds and one had close contact with the sick macaque, but was not injured or exposed to other body fluids and did not develop symptoms). The fourth person was the wife of one of the animal handlers. She used an ointment to treat her husband's lesions and subsequently used it on herself to treat contact dermatitis. The dermatitis progressed to pruritic lesions that were laboratory confirmed to contain B virus. All symptoms and viral shedding resolved with treatment. The study found no evidence of B virus infection among 130 close contacts of the 4 patients, healthcare workers, or primate workers. Moreover, even though B virus seroprevalence among adult macaques is >70%, only a few people in the study developed laboratory evidence of B virus infection. Thus, transmission of this virus, both human to human and primate to human, is quite rare.
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