This virus causes an acute febrile illness known as infectious mononucleosis (glandular fever), which occurs worldwide in adolescents and young adults. EBV is probably transmitted in saliva and by aerosol.
The predominant symptoms are fever, headache, malaise and sore throat. Palatal petechiae and a transient macular rash are common, the latter occurring in 90% of patients who have received ampicillin for the sore throat. Cervical lymphadenopathy, particularly of the posterior cervical nodes, and splenomegaly are characteristic. Mild hepatitis is common, but other complications such as myocarditis, meningit s, mesenteric adenitis and splenic rupture are rare. Although some young adults remain debilitated and depressed for some months after infection, the evidence for reactivation of latent virus in healthy individuals is controversial, although this is thought to occur in immunocompromised patients.
EBV infection should be strongly suspected if atypical mononuclear cells (glandular fever cells) are found in the peripheral blood. It can be confirmed during the second week of infection by a positive Paul-Bunnell reaction, which detects heterophile antibodies (IgM) that agglutinate sheep erythrocytes. False-positives can occur in other conditions such as hepatitis, Hodgkin’s disease and acute leukaemia. Specific EBV IgM antibodies indicate recent infection by the virus. The Monospot test is a sensitive and easily performed screening test. Clinically similar ill-nesses are produced by CMV and toxoplasmosis but these can be distinguished serologically.
The majority of cases require no specific treatment and recovery is rapid. Corticosteroid therapy is advised when there is neurological involvement, e.g. encephalitis, meningitis, Guillain-Barre syndrome or when there is marked thrombocytopenia or haemolysis. Corticosteroid therapy has also been used when malaise and intermittent fever are prolonged but this is not recommended. EBV is also considered to be the major aetiological agent responsible for Burkitt’s lymphoma and nasopharyngeal carcinoma. Human herpesvirus type 6 This recently discovered human herpesvirus infects T lymphocytes, occurs worldwide, and exists as a latent infection in over 90% of the adult population. The virus causes roseola infantum (exanthem subitum) which presents as a high fever followed by generalized macular rash in infants. Reactivation in the immunocompromised may lead to severe pneumonia.
Supportive management only is recommended for the common infantile disease. Ganciclovir can be used in the immunocompromised.
These small viruses tend to produce chronic infections, often with evidence of latency. They are capable of inducing neoplasia in some animal species and were among the first viruses to be implicated in tumorigenesis. Human papillomaviruses, of which there are many types, are responsible for the common wart and have been implicated in the aetiology of carcinoma of the cervix (types 16 and 18). The human BK virus, a polyomavirus, is generally found in immunosuppressed individuals and may be detected in the urine of between 15 and 40% of renal transplant patients, in patients receiving cytotoxic chemotherapy and in those with immunodeficiency states. A related virus, IC, is the cause of progressive multifocal leukoencephalopathy (PML) which presents as dementia in the immunocompromised and is due to progressive cerebral destruction resulting from accumulation of the virus in brain tissue.
Human parvovirus B19 produces:
• Erythema infectiosum (fifth disease), a common infection in schoolchildren. The rash is typically on the face (slapped-cheek appearance). The patient is well and the rash can recur over weeks or months.
• Asymptomatic infection occurs in 20% of children.
• Moderately severe self-limiting arthropathy .
• Aplastic crises in patients with chronic haemolysis, e.g. sickle cell disease.
• Chronic infection with anaemia in immunocompromised subjects.
This disease has been eradicated following an aggressive vaccination policy and careful detection of new cases.
This is a laboratory virus and does not occur in nature in either humans or animals. Its origins are uncertain but it is thought to be a derivative of the cowpox virus used by Jenner for vaccination against smallpox. Vaccination is now not recommended except for laboratory personnel handling certain poxviruses for experimental purposes.