Cohort profile: A Prospective Household cohort study of Influenza,Respiratory syncytial virus and other respiratory pathogens community burden and Transmission dynamics in South Africa, 2016–2018

PurposeThe PHIRST study (Prospective Household cohort study of Influenza, Respiratory Syncytial virus, and other respiratory pathogens community burden and Transmission dynamics in South Africa) aimed to estimate the community burden of influenza and respiratory syncytial virus (RSV) including the incidence of infection, symptomatic fraction, and to assess household transmission.ParticipantsWe enrolled 1684 individuals in 327 randomly selected households in a rural and an urban site over three consecutive influenza and two RSV seasons. A new cohort of households was enrolled each year. Participants were sampled with nasopharyngeal swabs twice‐weekly during the RSV and influenza seasons of the year of enrolment. Serology samples were collected at enrolment and before and after the influenza season annually.Findings to DateThere were 122 113 potential individual follow‐up visits over the 3 years, and participants were interviewed for 105 783 (87%) of these. Out of 105 683 nasopharyngeal swabs, 1258 (1%) and 1026 (1%) tested positive on polymerase chain reaction (PCR) for influenza viruses and RSV, respectively. Over one third of individuals had PCR‐confirmed influenza each year. Overall, there was influenza transmission to 10% of household contacts of an index case.Future PlansFuture planned analyses include analysis of influenza serology results and RSV burden and transmission. Households enrolled in the PHIRST study during 2016–2018 were eligible for inclusion in a study of SARS‐CoV‐2 transmission initiated in July 2020. This study uses similar testing frequency to assess the community burden of SARS‐CoV‐2 infection and the role of asymptomatic infection in virus transmission.     

High risk of occult hepatitis B virus infection in HIV-positive patients from South Africa.

This was a retrospective, unmatched case control, laboratory-based study, investigating the impact of human immunodeficiency virus (HIV) infection on the outcome of routine laboratory detection of HBsAg and prevalence of active HBV infection in 295 samples from 167 HIV-positive and 128 HIV-negative patients. The samples were tested for HBV (HBsAg, anti-HBc, anti-HBs, HBeAg and anti-HBe) and anti-HIV 1 and 2 (Axsym assays, Abbott Laboratories), as part of routine diagnosis. A nested PCR assay, with detection limit of 800 copies/ml and employing independent sets of primers to core and surface genes, was used to investigate HBV DNA. Quantification of HBV DNA was determined with the Cobas Amplicor HBV Monitor assay (Roche Diagnostics). Of the 295 samples, the frequency of anti-HBc was almost similar; 82% for the HIV-negatives and 85% for the HIV-positives, indicating that both groups were equally exposed to HBV infection. The HIV-positives had a higher rate of anti-HBs (76.0% versus 47.7%) and a lower rate of HBsAg carriage (16.2% versus 35.2%), suggesting that HIV-positive individuals are less likely to experience chronic HBV infection. However, analysis of HBV DNA indicated that many of the anti-HBs positives (20.5% versus 8.2%) and HBsAg-negatives (22.1% versus 2.4%) had active HBV infection in the HIV-positive group. There was a statistically significant difference in the prevalence of HBV DNA in the HBsAg-negatives between the two groups (Odds ratio: 11.52; chi-square: p=0.00006). Additionally, 33.3% (5/15) of sera with "anti-HBc alone" serological pattern were HBV viremic in the HIV-positive group, compared to 0% (n=31) in the HIV-negatives. Quantification of HBV DNA from HBsAg-negative/HIV-positive patients demonstrated low level HBV viremia (below 10,000 copies/ml). In conclusion, these findings strongly support that HIV infection is a risk factor for occult HBV infections.     

Increased exposure to hepatitis B virus infection in HIV-positive South African antenatal women

The prevalence of markers for hepatitis B virus (HBV) exposure and active infection in HIV-positive (n=710) and HIV-negative (n=710) pregnant South African women was investigated. The following statistically significant increases in the HIV-positive group were found: anti-hepatitis B core antigen (anti-HBc) (37.3% versus 28.6%; odds ratio [OR]: 1.49); anti-hepatitis B surface antigen (anti-HBs) (29.5% versus 20.1%; OR: 1.66); exposure based on hepatitis B surface antigen (HBsAg) and anti-HBc (39.2% versus 30.1%; OR: 1.49); and exposure based on anti-HBs, anti-HBc and HBsAg (37.1% versus 24.5%; OR: 1.82). However, there was no increase in active HBV infections, with 2.4% of the HIV positives and 2.2% of the HIV negatives being HBV DNA positive. Although the impact that HIV has had on the prevalence of HBV in this population group is not as pronounced as that found in areas of low endemicity (where up to seven-fold increases have been reported), there is a statistically significant increased exposure to HBV.