Acquisition of Cytomegalovirus Infection: an Update

Human cytomegalovirus (CMV) is a ubiquitous deoxyribonucleic acid virus that commonly infects a majority of individuals at some time during their life. Although most of these CMV infections are asymptomatic, certain patient groups are at risk to develop serious illness. Understanding the epidemiology of this virus is a key element in the development of strategies for preventing CMV disease. However, a number of features of this virus complicate such understanding. Following infection, CMV can remain latent, with subsequent reactivation; the factors controlling latency and reactivation and those factors which determine whether a CMV infection will be symptomatic are unknown. CMV disease can be acquired by natural routes, including horizontal and vertical transmission. Due to the ubiquity of CMV, the delineation of CMV transmission by these natural routes is complicated by the myriad of possible sources. Moreover, concerns over the risk of CMV transmission to the seronegative pregnant female have been raised in relation to preventing CMV transmission. By using molecular biologic techniques, much knowledge has been gained regarding the transmission of CMV disease by natural routes; however, a number of questions remain unanswered. The transmission of CMV infection by natural routes is therefore reviewed and the issues are highlighted. Primary infection, reactivation, and reinfection are the types of active CMV infections that can occur in an immunocompromised patient. In addition to natural routes of infection, introduction of presumably latently infected organs and requirements for multiple blood transfusions increase potential exposure to CMV in the immunocompromised patient. Understanding the epidemiology of CMV infections in the immunocompromised patient is difficult and in some instances controversial due to the complexity and interdependency of a number of factors which lead to CMV infection. In an immunocompromised individual, a major risk factor in developing overt CMV-related disease is associated with the serological status of an organ donor, the recipient, and the blood product given to these patients. In addition, a large body of inferential data supports the transmission of CMV by blood products or organs from seropositive donors; however, the mechanisms by which transmission occurs remain unclear. The possible sources and mechanisms of transmission of CMV infections in the immunocompromised host are reviewed. Lastly, strategies for the ultimate prevention of CMV disease are discussed in light of the epidemiology of CMV infections. To date, these strategies have included use of CMV-seronegative blood products or organs, antiviral agents, and vaccines.(ABSTRACT TRUNCATED AT 400 WORDS)