Author(s): Sara A Healy 1 2 3 , Sonia Gupta 4 , Ann J Melvin [*] 5 3
antiviral treatment; coinfection; drug resistance; HBV; hepatitis B; HIV; pediatrics; vaccine
Epidemiology of HIV/HBV coinfection
Approximately 350 million people are chronically infected with HBV, and 500,000-1,200,000 die each year of HBV-related disease and hepatocellular carcinoma [1-3] . Although the prevalence varies from population to population, approximately 5-10% of HIV-infected adults worldwide also have chronic HBV infection, defined as persistence of hepatitis B surface antigen (HBsAg) for >6 months. HIV/HBV coinfection in some sub-Saharan African populations is believed to be significantly higher [3-5] .
Prevalence of HIV/HBV coinfection in pregnant women
Given that HIV and HBV have common transmission routes (perinatal, horizontal, parenteral, sexual) and that endemic regions of both often overlap, as might be predicted, a number of studies have shown that the prevalence of HBV infection among HIV-positive individuals is significantly higher than in HIV-negative individuals [6-9] . However, information on the magnitude of HBV positivity of different risk groups, including people living with HIV/AIDS, is scarce, especially in high-risk populations, such as pregnant women. Recently, with the availability of nationally approved combination antiretroviral therapy (cART) programs, there has been increased concern regarding the potentially high prevalence of HBV coinfection in HIV-positive pregnant women. This concern has spawned further evaluations into the true seroprevalence of HBV infection on a national level, including in African countries that were previously underrepresented (Table 1) [10-22] . As demonstrated in Table 1, prevalence of HBV monoinfection among pregnant women in Africa ranges from 4.0 to 17.1%, and prevalence of HBV/HIV-coinfected pregnant women in Africa is variable with a range from 0.4 to 7.1%.
Prevalence of HIV/HBV coinfection in children
The prevalence of chronic viral hepatitis in HIV-infected children is not well characterized. The authors of this paper examined literature on the coinfection of HIV and HBV in children published since 2000. A Medline search was conducted using Ovid's online search engine. Keywords included 'HIV,' 'AIDS,' 'hepatitis B' and 'children.' The starting year was defined as 2000 and the end date was not defined. Any 'related article' hyperlinks were followed for each retrieved article. The reference list of the retrieved articles was also used to identify related literature. No language priority was chosen. The results of this search yielded the studies listed in Table 2 [23-34] . In highly endemic ([greater than or equal]8% of the population are HBsAg positive) areas of Africa and Asia, most HBV infections occur in the first 5 years of life  . It has been estimated that three million people from sub-Saharan Africa are coinfected with HIV and HBV, many of them may be immunotolerant children [29,36] . Given that both HBV and HIV can be transmitted perinatally and infants exposed to HBV are more likely to develop chronic HBV infection, HBV infection in HIV-infected children would be expected to be higher than the prevalence in the general pediatric population.
Coinfection & risk of transmission
Perinatal transmission worldwide is the most common mode of HBV transmission. However, mother-to-infant transmission...