B Virus (Macacine Herpesvirus 1, Herpes B) Clinical Presentation

Updated: Oct 22, 2021
  • Author: Sandra G Gompf, MD, FACP, FIDSA; Chief Editor: Pranatharthi Haran Chandrasekar, MBBS, MD  more...
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The incubation period of B virus infection ranges from 2 to 30 days, with progression of symptoms over 7 to 10 days. After potential exposure to B virus in humans, the individual exposed and the primate (if available) should be monitored (see Laboratory Studies).

Early symptoms (variably present) may include the following [1] :

  • Pain or pruritus at exposure site
  • Vesicles or ulcers at or near exposure site
  • Local lymphadenopathy or lymphadenitis

Intermediate symptoms (variably present) may include the following [1] :

  • Fever
  • Malaise
  • Diffuse myalgias
  • Headache
  • Numbness or paraesthesias at or near exposure site
  • Nausea and/or abdominal pain
  • Persistent hiccups

Late manifestations may include the following [1] :

  • Persistent headache
  • Alteration of mentation
  • Focal neurological symptoms

Physical Examination

Findings of B virus infection include progressive neurologic deterioration that suggests a multifocal hemorrhagic encephalitis or encephalomyelitis. This finding contrasts with the temporal lobe localization of herpes simplex encephalitis. The progression of signs and symptoms may be modified by early antiviral therapy. Asymptomatic human B virus infection is unknown, if not nonexistent. Typical physical signs include the following [1] :

  • Meningismus
  • Confusion progressing to coma
  • Brain stem findings, which may include diplopia, dysarthria, dysphagia, cerebellar signs (including ataxia), and/or cranial nerve palsies
  • Signs of meningoencephalomyelitis, which may include seizures, hemiparesis or hemiplegia, progressive ascending paralysis, and/or transverse myelitis
  • Non-CNS signs, which may include conjunctivitis, chorioretinitis, and/or sinusitis


Aseptic meningitis results in a moderate lymphocyte pleocytosis and erythrocytes, moderately elevated cerebrospinal fluid (CSF) protein level, and normal CSF glucose. In humans, B virus can be grown from CSF, skin lesions, and urine.

Nonfatal cases of human B virus infection may result in complete recovery, but residua are common and include the following:

  • Extremity paresis or plegia
  • Aphasia
  • Dysarthria
  • Residual chorioretinitis

Because of prolonged or long-term use of antiviral therapy in surviving patients, the frequency of asymptomatic or symptomatic reactivation and/or viral shedding occur is unclear. [1]