Epidemiology of CMV Infection

Cytomegalovirus is a double-stranded DNA virus belonging to the human herpesvirus family (1,5). The other members include herpes simplex virus (HSV), varicella zoster virus (VZV), and Epstein-Barr virus (EBV). While the herpesviruses are 

It is rare for patients with CD4+ counts greater than 200 cells/mm3 to develop this disease, although it could potentially occur in an individual who previously had a very low CD4+ count less than 50 cells/mm3 who is initially experiencing a favorable response to HAART with rapid elevation of the CD4+ count (4). 

Highly active antiretroviral therapy, also known as HAART, refers to a combination of medications to treat HIV infection including protease inhibitors and/or nucleoside analogues. It has been defined as an antiretroviral regimen that can be expected to reduce the viral load to less than 50 copies per milliliter in treatment of naive patients (23). The use of HAART in developed countries commenced in 1995 1996 and it has markedly improved survival in AIDS. The increased CD4+ lymphocyte cell count and the decreased HIV viral load in the peripheral blood secondary to HAART in patients who respond to this therapy, results in a reduction of all opportunistic infections including CMV retinitis (4). Since the introduction of HAART, there has been reduction in the incidence of primary and relapsing CMV disease, CMV viral load and antigenemia (24). The North American incidence of CMV retinitis in the post-HAART era has decreased to approximately one-fourth that of the pre-HAART era (4,24 27). 

CMV disease may still develop or relapse when HAART is not effective or the CD4+ count remains low. As well, incomplete immune recovery may not fully protect against CMV retinitis. Furthermore, HAART medications may not be easily obtained, especially in some underdeveloped countries. For these reasons, CMV retinitis continues to be a prevalent and serious opportunistic infection in AIDS. It is important to be aware of the features and treatment options for this potentially multisystemic infection in AIDS and other immunocompromised individuals. The treatment of CMV retinal infection remains challenging, especially due to the multiple side effects of anti-CMV medications. 

---