Herpes simplex virus type 2 in sub-Saharan Africa and the potential impact of helminth immune modulation

Abstract

Herpes simplex virus type 2 (HSV-2) and helminth infections are among the most widespread infectious diseases in sub-Saharan Africa (SSA). Helminths are known to modulate host immune responses and consequently impact the severity and outcomes of unrelated diseases, including allergies, autoimmune conditions, and infectious diseases. In this way, helminths may modulate essential immune responses against HSV-2 during co-infection and may alter susceptibility to and pathology of HSV-2. However, the epidemiology of STH/HSV-2 co-infections is understudied, and whether helminths influence the host immune response to HSV-2 is not well understood. In this perspective piece, we briefly examine the current knowledge on helminth immune modulation of important pathogens that are endemic to SSA, arguing that it is important to explore HSV-2 and helminth co-infections to elucidate potential interactions between HSV-2 and helminths. This is particularly relevant in SSA, where both pathogens are highly prevalent.

Keywords: HSV-2; HSV-2 outcomes; co-infection; helminth immune modulation; helminths; sub-Saharan Africa.

Figure 1

Estimated numbers (n) and proportions (%) of STH PC required for pre-SAC and SAC, Status of Schistosomiasis in endemic countries, and HSV-2 infections. STH PC: Soil-transmitted helminths Preventive Chemotherapy [Data presented is the estimated number of Pre-school Aged (Pre-SAC) and School-Aged Children (SAC) requiring PC for STHs in 2022^a; % Proportion = Estimated number of STH PC/Estimated number of Global STH PC x 100]; Schisto: Status of Schistosomiasis in endemic countries in 2022^b; % Proportion = Estimated number of Schistosoma/Estimated number of Global Schistosoma PC x 100]; HSV-2: Herpes Simplex Virus Type II [Data presented is the estimated number of people within the 15-49 year age group that were infected with HSV-2 in 2016^c; % Proportion = Estimated number of HSV-2/Estimated number of Global HSV-2 x 100, Source of WHO regions map^d. ^aSource: Adapted from (World Health Organisation, 2024c). ^bSource: Adapted from (World Health Organisation, 2024a). ^cSource: Adapted from (James et al., 2020). ^dSource: Adapted from (Our World in Data, 2023).