Mononucleosis
Identification--An acute viral syndrome characterized clinically by fever, sore throat (often with exudative pharyngotonsillitis), lymphadenopathy (especially posterior cervical) and splenomegaly; characterized hematologically by mononucleosis and lymphocytosis of 50% or greater, including 10% or more atypical cells; and characterized serologically by the presence of heterophile and Epstein-Barr virus (EBV) antibodies.
Recovery usually occurs in a few weeks, but a very small proportion of individuals can take months to regain their former level of energy. There is no evidence that this is due to abnormal persistence of the infection in a chronic form.
In young children the disease is generally mild and more difficult to recognize. Jaundice occurs in about 4% of infected young adults, although 95% will have abnormal liver function tests; splenomegaly occurs in 50%.
Duration is from 1 to several weeks; the disease is rarely fatal. The disease is more severe in older adults. The causal agent, EBV, is also closely associated with the pathogenesis of several lymphomas and nasopharyngeal cancer (see Malignant neoplasms associated with infectious agents). Fatal immunoproliferative disorders involving a polyclonal expansion of EBV infected B-lymphocytes may occur in persons with an X-linked recessive immunoproliferative disorder; they can also occur in persons with acquired immune defects, including patients infected with HIV, transplant recipients and persons with other conditions requiring long-term immunosuppressive therapy.
About 10%--15% of infectious mononucleosis cases are heterophilenegative. A heterophile-negative form of a syndrome resembling infectious mononucleosis is due to cytomegalovirus and accounts for 5% to 7% of the "mono syndrome" (see Cytomegalovirus infections); other rare causes are toxoplasmosis and herpesvirus type 6 (see Exanthema subitum following rubella). A mononucleosis-like illness may occur early in HIV-infected patients. Differentiation depends on laboratory results that include the EBV IgM test; only EBV elicits the "true" heterophile antibody. EBV accounts for over 80% of both heterophile positive and heterophile negative cases of the mononucleosis syndrome.
Laboratory diagnosis is based on the finding of a lymphocytosis exceeding 50% (including 10% or more abnormal forms), abnormalities in liver function tests (AST) or an elevated heterophile antibody titre after adsorption of the serum on guinea pig kidney. The most sensitive and commercially available test is the absorbed horse-RBC test; the most specific of the common tests the beef-cell hemolysin test; and the most frequently used procedure a commercial, qualitative slide agglutination assay. Very young children may not show an elevation of the heterophile titre, and heterophile-negative and clinically atypical forms rarely occur in the elderly. If available, the IFA test for IgM and IgA antibody specific for viral capsid antigen (VCA) or antibody against "early antigen" of the causal virus is helpful in diagnosis of heterophile-negative cases; antibody specific for the EBV nuclear antigen (EBNA) is usually absent during the acute phase of illness. Therefore, a positive anti-VCA titre and a negative anti-EBNA titre are diagnostic responses of an early primary EBV infection.
Infectious agent--Epstein-Barr virus, human (gamma) herpesvirus 4, closely related to other herpesviruses morphologically, but distinct serologically; it infects and transforms B-lymphocytes.
Occurrence--Worldwide. Infection is common and widespread in early childhood in developing countries and in socioeconomically depressed population groups, where it is usually mild or asymptomatic. Typical infectious mononucleosis occurs primarily in industrialized countries, where age of infection is delayed until older childhood and young adulthood, so that it is most commonly recognized in high school and college students. About 50% of those infected develop clinical infectious mononucleosis; the others are mostly asymptomatic.
Reservoir--Humans.
Mode of transmission--Person-to-person spread by the oropharyngeal route, via saliva. Young children may be infected by saliva on the hands of nurses and other attendants and on toys, or by prechewing of baby food by the mother, a practice in some countries. Kissing facilitates spread among young adults. Spread may also occur via blood transfusion to susceptible recipients, but ensuing clinical disease is uncommon. Reactivated EBV may play a role in the interstitial pneumonia of HIV infected infants and in hairy leukoplakia and B-cell tumours in HIV-infected adults.
Incubation period--From 4 to 6 weeks.
Period of communicability--Prolonged; pharyngeal excretion may persist in cell-free form for a year or more after infection; 15%--20% or more of EBV antibody-positive healthy adults are long-term oropharyngeal carriers.
Susceptibility--Susceptibility is general. Infection confers a high degree of resistance; immunity from unrecognized childhood infection may account for low rates of clinical disease in lower socioeconomic groups. Reactivation of EBV may occur in immunodeficient individuals and result in elevated antibody titres to EBV but not heterophile antibody, and possibly to the development of lymphomas.
Methods of control--
A. Preventive measures: Undetermined. Use hygienic measures including handwashing to avoid salivary contamination from infected individuals; avoid drinking beverages from a common container to minimize contact with saliva.
B. Control of patient, contacts and the immediate environment:
1) Report to local health authority: Official report not ordinarily
justifiable, Class 5 (see Reporting).
2) Isolation: Not applicable.
3) Concurrent disinfection: Of articles soiled with nose and
throat discharges.
4) Quarantine: Not applicable.
5) Immunization of contacts: Not applicable.
6) Investigation of contacts and source of infection: For the
individual case, of little value.
7) Specific treatment: None. Nonsteroidal anti-inflammatory
drugs, or steroids given in small doses in decreasing amounts
over about a week are of value in severe toxic cases and in
patients with severe oropharyngeal involvement and airway
encroachment.
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Recovery usually occurs in a few weeks, but a very small proportion of individuals can take months to regain their former level of energy. There is no evidence that this is due to abnormal persistence of the infection in a chronic form.
In young children the disease is generally mild and more difficult to recognize. Jaundice occurs in about 4% of infected young adults, although 95% will have abnormal liver function tests; splenomegaly occurs in 50%.
Duration is from 1 to several weeks; the disease is rarely fatal. The disease is more severe in older adults. The causal agent, EBV, is also closely associated with the pathogenesis of several lymphomas and nasopharyngeal cancer (see Malignant neoplasms associated with infectious agents). Fatal immunoproliferative disorders involving a polyclonal expansion of EBV infected B-lymphocytes may occur in persons with an X-linked recessive immunoproliferative disorder; they can also occur in persons with acquired immune defects, including patients infected with HIV, transplant recipients and persons with other conditions requiring long-term immunosuppressive therapy.
About 10%--15% of infectious mononucleosis cases are heterophilenegative. A heterophile-negative form of a syndrome resembling infectious mononucleosis is due to cytomegalovirus and accounts for 5% to 7% of the "mono syndrome" (see Cytomegalovirus infections); other rare causes are toxoplasmosis and herpesvirus type 6 (see Exanthema subitum following rubella). A mononucleosis-like illness may occur early in HIV-infected patients. Differentiation depends on laboratory results that include the EBV IgM test; only EBV elicits the "true" heterophile antibody. EBV accounts for over 80% of both heterophile positive and heterophile negative cases of the mononucleosis syndrome.
Laboratory diagnosis is based on the finding of a lymphocytosis exceeding 50% (including 10% or more abnormal forms), abnormalities in liver function tests (AST) or an elevated heterophile antibody titre after adsorption of the serum on guinea pig kidney. The most sensitive and commercially available test is the absorbed horse-RBC test; the most specific of the common tests the beef-cell hemolysin test; and the most frequently used procedure a commercial, qualitative slide agglutination assay. Very young children may not show an elevation of the heterophile titre, and heterophile-negative and clinically atypical forms rarely occur in the elderly. If available, the IFA test for IgM and IgA antibody specific for viral capsid antigen (VCA) or antibody against "early antigen" of the causal virus is helpful in diagnosis of heterophile-negative cases; antibody specific for the EBV nuclear antigen (EBNA) is usually absent during the acute phase of illness. Therefore, a positive anti-VCA titre and a negative anti-EBNA titre are diagnostic responses of an early primary EBV infection.
Infectious agent--Epstein-Barr virus, human (gamma) herpesvirus 4, closely related to other herpesviruses morphologically, but distinct serologically; it infects and transforms B-lymphocytes.
Occurrence--Worldwide. Infection is common and widespread in early childhood in developing countries and in socioeconomically depressed population groups, where it is usually mild or asymptomatic. Typical infectious mononucleosis occurs primarily in industrialized countries, where age of infection is delayed until older childhood and young adulthood, so that it is most commonly recognized in high school and college students. About 50% of those infected develop clinical infectious mononucleosis; the others are mostly asymptomatic.
Reservoir--Humans.
Mode of transmission--Person-to-person spread by the oropharyngeal route, via saliva. Young children may be infected by saliva on the hands of nurses and other attendants and on toys, or by prechewing of baby food by the mother, a practice in some countries. Kissing facilitates spread among young adults. Spread may also occur via blood transfusion to susceptible recipients, but ensuing clinical disease is uncommon. Reactivated EBV may play a role in the interstitial pneumonia of HIV infected infants and in hairy leukoplakia and B-cell tumours in HIV-infected adults.
Incubation period--From 4 to 6 weeks.
Period of communicability--Prolonged; pharyngeal excretion may persist in cell-free form for a year or more after infection; 15%--20% or more of EBV antibody-positive healthy adults are long-term oropharyngeal carriers.
Susceptibility--Susceptibility is general. Infection confers a high degree of resistance; immunity from unrecognized childhood infection may account for low rates of clinical disease in lower socioeconomic groups. Reactivation of EBV may occur in immunodeficient individuals and result in elevated antibody titres to EBV but not heterophile antibody, and possibly to the development of lymphomas.
Methods of control--
A. Preventive measures: Undetermined. Use hygienic measures including handwashing to avoid salivary contamination from infected individuals; avoid drinking beverages from a common container to minimize contact with saliva.
B. Control of patient, contacts and the immediate environment:
1) Report to local health authority: Official report not ordinarily
justifiable, Class 5 (see Reporting).
2) Isolation: Not applicable.
3) Concurrent disinfection: Of articles soiled with nose and
throat discharges.
4) Quarantine: Not applicable.
5) Immunization of contacts: Not applicable.
6) Investigation of contacts and source of infection: For the
individual case, of little value.
7) Specific treatment: None. Nonsteroidal anti-inflammatory
drugs, or steroids given in small doses in decreasing amounts
over about a week are of value in severe toxic cases and in
patients with severe oropharyngeal involvement and airway
encroachment.