Elsevier

Annals of Epidemiology

Volume 20, Issue 12, December 2010, Pages 958-963
Annals of Epidemiology

Brief Communication
Geographic Heterogeneity of Prevalence of the Human Herpesvirus 8 in Sub-Saharan Africa: Clues About Etiology

https://doi.org/10.1016/j.annepidem.2010.07.098Get rights and content

Purpose

Human herpesvirus 8 (HHV-8, or Kaposi sarcoma [KS]-associated herpesvirus, KSHV) is a necessary but insufficient cause of KS, as KS develops in few HHV-8-infected persons. In sub-Saharan Africa, marked differences in the geographic distribution of HHV-8 and KS suggest that environmental cofactors influence HHV-8 transmission, control, and progression to KS. However, a direct comparison of HHV-8 prevalence estimates is complicated because studies used different serologic assays and analytic methods. We assessed HHV-8 seropositivity in several African countries with heterogeneous environments and varying KS incidence using a unified approach.

Methods

HHV-8 antibodies were measured among 3196 adults (aged 20+ years) and 2404 children (aged <20 years) from five studies in four sub-Saharan countries in Africa. Serum samples were tested by the same laboratory using K8.1 and orf73 enzyme immunoassays.

Results

Children’s HHV-8-seropositivity ranged from 18.1% in Kampala, Uganda, to 33.8% in North Mara, Tanzania, increasing steeply with age in all populations. Among adults, HHV-8-seropositivity ranged from 23.5% in Nigeria to 70.6% in rural West Nile, Uganda. It was higher in males and rural areas.

Conclusions

Our data indicate that geographical exposures, gender, age, and factors correlated with rural residence impact HHV-8 seropositivity in sub-Saharan Africa.

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

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