Measles in Sudan: Diagnosis, Epidemiology and Humoral Immune Response

Despite the availability of safe and effective live attenuated vaccines, measles remains endemic in many developing countries. Little is known about the pathogenesis of measles virus (MV) infections in the areas of itsendemicity, largely due to the limited infrastructure and political instability. Whereas measles in industrialised countries is often considered an “innocent” childhood disease, measles case-fatality rates are often well above 1% in developing countries, and can be even higher in outbreak situations (5). Oneexplanation for this observation is that measles is associated with a transient immunosuppression resulting in an increased susceptibility to other infectious agents: the infectious pressure of many human pathogens is substantially higher in developing countries than in the industrialised world. Incombination with vitamin deficiencies (e.g. vitamin A) and inadequate case management this increases the risk of MV infection developing into a serious life-threatening disease (3). However, prior to or co-infections with otherpathogens could also play a role in modifying the specific immune responseto MV infection. In particular the high prevalence of parasitic infections inmany developing countries could affect the development of the cellular immune system towards a dominance of T-helper (Th) cells producing type 2 cytokines such as IL-4, IL-5 IL-10 and IL-13. Such responses have beenassociated with immunosuppression (197), and counterbalance Th responsesproducing type 1 cytokines (such as IL-12 and interferon-γ) which sustaincytotoxic T cell (CTL) response and have been associated with clearance ofMV infection (198). Towards the control and eventual eradication of measles more insight will be required in the pathogenesis of measles in areas of its endemicity. However, another reason to study measles in these regions is that it allows the development and validation of alternative surveillance methods. Surveillance will become of crucial importance during the next decade(s),since several organisations including the World Health Organisation (WHO), United Nation Children’s funds (UNICEF), the American Red Cross and the Centres for Disease Control (CDC) have recently joined forces to proceed toa phase of accelerated measles control which should result in a substantialreduction in measles mortality (118), (www.measlesinitiative.org). It has been shown that in areas with decrease MV circulation the clinical diagnosis of measles becomes increasingly unreliable, and other rash-causing diseases such as those caused by infection with rubella virus, parvovirus B19, orhuman herpesvirus-6 are often mistaken for measles (199). We have studied diagnostic, virological and immunological aspects ofmeasles in suburban Khartoum, Sudan. Prospective studies were carried outin two cohorts of clinically diagnosed measles cases.