Brief CommunicationGeographic Heterogeneity of Prevalence of the Human Herpesvirus 8 in Sub-Saharan Africa: Clues About Etiology
Introduction
Human herpesvirus 8 (HHV-8, also known as Kaposi sarcoma (KS)-associated herpesvirus, KSHV), is a necessary but insufficient cause of KS (1). Globally, HHV8 seropositivity varies by geography, and KS develops in only a very small proportion of HHV-8-infected persons, suggesting environmental or genetic cofactors influence risk. HHV-8 seropositivity is highest in sub-Saharan Africa, intermediate in Mediterranean countries, and low in North America and Northern Europe. HHV-8 spreads via contact with infected saliva during childhood in areas with high HHV-8 seroprevalence and high KS incidence. In contrast, HHV-8 transmission is associated with homosexual contact in areas of low HHV-8 and KS incidence (2). Whether HHV-8 transmission is associated with heterosexual contact is less clear, with some studies providing supportive evidence 3, 4 whereas others do not (5).
The varying geographic distributions of HHV-8 seropositivity and KS incidence remain puzzling, especially in sub-Saharan Africa. For example, HHV-8 seropositivity is high in Eastern and Central Africa (70%–90%) where KS is endemic; but seropositivity is low in Western, Northern, and Southern Africa (10%–20%) (6), where KS is rare. Yet pockets of high HHV-8 seropositivity have been reported in The Gambia (65%) in Western Africa and in Botswana (80%) in Southern Africa, although KS seems to be rare in those countries. However, a direct comparison of HHV-8 seropositivity for different populations is complicated because studies used different serologic assays, with no gold standard to define HHV-8 seropositivity.
We therefore re-analyzed five of our HHV-8 seroepidemiology studies, conducted in four countries in sub-Saharan Africa with diverse geographical features, using a unified approach to obtain new, comparable estimates of HHV-8 seropositivity. We assessed variation of HHV-8 seroprevalence and possible cofactors. These estimates and associations may provide further clues to cofactors that may influence HHV-8 transmission, control, and progression to KS and help formulate novel hypotheses for the geographic variation of KS and HHV-8.
Section snippets
Study Populations
The data were from five studies conducted in four countries, Nigeria, Uganda, Kenya, and Tanzania, using archival serum samples collected between 1972 and 2002. In Lagos, Nigeria, during 1991, 1992, and 1994, 1888 adults and 219 children were enrolled, including a sample from the general population, patients attending a sexually transmitted disease (STD) clinic, and commercial sex workers (7). At Mulago Hospital in Kampala, Uganda, 599 children attending a sickle cell clinic and 517 of their
Results
Demographic characteristics of the five populations are described in Table 1, and HHV-8 seropositivity estimates are given in Table 2. HHV-8 seropositivity was much lower in Ugandan children from Kampala (18.1%), an urban area, than in children from the West Nile District (33.6%), a rural area, and it also was high in the children from East Africa (42.4%) and Tanzania (33.8%; Table 2), both rural areas. Notably, HHV-8 seropositivity was higher among Nigerian children (24.6%) than Ugandan
Discussion
We showed striking variation in HHV-8 seropositivity by age and geography, using data from five diverse populations in sub-Saharan Africa, subjected to the same testing and statistical procedures. Seropositivity increased steeply during childhood, consistent with intense HHV-8 transmission among children. This finding agrees with results by Butler et al. (15) suggesting significant and ongoing prepubertal HHV-8 infection among children in Eastern Africa. HHV-8 seropositivity increased with age
References (26)
Diagnosis and epidemiology of human herpesvirus 8 infection
Semin Hematol
(2003)Endemic Kaposi-sarcoma in Africa and local volcanic soils
Lancet
(1993)- et al.
Risk of classic Kaposi sarcoma with residential exposure to volcanic and related soils in Sicily
Ann Epidemiol
(2009) - et al.
Soil silicates and Kaposi’s Sarcoma in Sardinia
Lancet
(1995) - et al.
Identification of herpesvirus-like DNA sequences in AIDS-associated Kaposi’s sarcoma
Science
(1994) - et al.
Antibodies against human herpesvirus 8 in black South African patients with cancer
N Engl J Med
(1999) - et al.
Human herpesvirus 8: seroprevalence and correlates in prostitutes in Mombasa, Kenya
J Infect Dis
(2003) - et al.
Geographic variation in the prevalence of Kaposi Sarcoma-associated herpesvirus and risk factors for transmission
J Infect Dis
(2009) - et al.
Review of the distribution of Kaposi’s sarcoma-associated herpesvirus (KSHV) in Africa in relation to the incidence of Kaposi’s sarcoma
Br J Cancer
(2003) - et al.
Transmission of human herpesvirus 8 by sexual activity among adults in Lagos, Nigeria
AIDS
(2002)