B virus: Description, Causes and Risk Factors:
An herpesvirus, in the family Herpesviridae, affecting Old World monkeys, that is very similar morphologically to herpes simplex virus; fatal infection may occur in humans following the bite of an infected monkey, although other modes of transmission have also been documented.
B virus is a zoonotic agent that can cause fatal encephalomyelitis in humans. The virus naturally infects macaque monkeys, resulting in disease that is similar to herpes simplex virus infection in humans. Although B virus infection generally is asymptomatic or mild in macaques, it can be fatal in humans.
B virus is a naturally occurring infectious agent that is endemic among macaque monkeys (including rhesus macaques, pig-tailed macaques, cynomolgus monkeys, and other macaques). Animals become infected with the virus primarily through exposure of the mucosa or skin to oral or genital secretions from other monkeys. Vertical transmission of the virus to neonates is rare. Infected monkeys often have no or very mild symptoms, although oral and genital lesions may develop. The virus persists in the sensory ganglia for the Lifetime of the animal and can reactivate, resulting in the shedding of infectious virus from the oral, conjunctival, or genital mucosa of animals with or without visible lesions.
Infections due to B virus in humans are rare and occur as a result of exposure to either macaques or their secretions or tissues. The incubation period for infection in humans after an identi?ed exposure is reported to range from 2 days to 5 weeks; most well documented cases present 5-21 days after exposure. Some patients present with a progression of symptoms that ?rst appear near the site of exposure; others present with symptoms limited to the peripheral nervous system or CNS. A third presentation involves ?u-like illness with fever, chills, myalgias, and other non-speci?c symptoms, with no focal ?ndings, and it may later be followed by the abrupt onset of CNS symptoms.
After infecting humans, B virus replicates at the site of exposure and may result in the development of a vesicular rash at this site. Additional symptoms can include tingling, itching, pain, or numbness at the site; however, many patients have no symptoms at the site of infection. Some patients develop lymphadenopathy proximal to the site of inoculation. Within the ?rst 3 weeks after exposure, paresthesias may develop and proceed proximally along the affected extremity. Associated symptoms can include fever, myalgias, weakness of the affected extremity, abdominal pain, sinusitis, and conjunctivitis. Other organs, including the lung and liver, may be involved.
Because con?rmed cases of B virus infection have occurred in Animal caretakers who work with macaques but who do not recall obvious exposures, workers need to be aware that any episode of prolonged fever (for 148 h), ?ulike symptoms, or symptoms compatible with B virus infection, even in the absence of a known exposure, needs to be reported to their supervisor and to occupational health care personnel.
Symptoms ofinfection can include meningismus, nausea
, vomiting, persistent headache, confusion, diplopia, dysphagia, dizziness, dysarthria, cranial nerve palsies, and ataxia. Seizures, hemiplegia,hemiparesis, ascending paralysis, respiratory failure, and comamore commonly occur later in the course of infection.
Identi?cation of virus at the site of exposure or in a wounddoes not prove infection with the virus. However, a positiveculture or PCR result indicating the presence of viral DNAeither at a site not directly associated with the exposure (e.g.,the conjunctiva, in the case of a bite), or in a wound or at asite of exposure concurrent with symptoms compatible with Bvirus disease should be considered indicative of infection.
The use of PCR forthe detection of B virus might provide more-rapid results thandoes culture; however, there is less experience in how to interpret a positive PCR result, because it is not clear that replication-competent virus is present if a wound is found to bepositive for viral DNA by PCR analysis. B virus was not detectedby PCR in a published study of wound swab samples.
The most critical period for the prevention of B virus infection and other infections is during the ?rst few minutes after an exposure occurs. Both the adequacy and the timeliness of wound or mucosa cleansing are the most important factors for reducing the risk of infection. Primate workers should be instructed to immediately cleanse the skin or mucosa affected by bites, scratches, or exposure to any potentially infected material from macaques. Washing of the involved site should last for at least 15 min.
Eyes or mucous membranes potentially exposed to B virus should be irrigated immediately with sterile saline solution or water for 15 min. If reaching the nearest eye-washing station requires a delay of more than a few minutes, then a kit that contains a 1-L bag of sterile saline should be available at the work site. If the worker is based at a remote location, he or she should transport a 1-L bag of saline to that site, so there will not be a delay in cleansing the wound or mucosa.
Potentially exposed skin should be washed with povidone-iodine, chlorhexidine, or detergent soap. These solutions can destroy the virus lipid envelope and inactivate virus on the skin; however, they are too harsh to use when washing the eye or mucous membranes.
Three orally administered agents — acyclovir (ZoviraxSM
), valacyclovir (ValtrexSM
), and famciclovir (FamvirSM
) — are currently available for postexposure prophylaxis of B virus infection. These drugs have not been approved by The US Food and Drug Administration for treatment of B virus infection.
NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.