In Nigeria, HIV prevalence (1.4 percent among adults) is relatively low. However, with the country’s huge population (estimated at 211 million), HIV infection still remains a public health issue – one that requires a systematic and tailored intervention. One of such specially-designed interventions is a study to identify new modes of HIV transmission.
It was done by the National Agency for the Control of AIDS (NACA), in collaboration with development partners, as part of strategies to halt the spread of infections.
To this end, the Mode of Transmission Study (MOT), which focused on identifying the sources of new HIV infections and was first conducted in 2009, was repeated using an updated model known as the Incidence Pattern Model (IPM).
According to NACA Director-General, Dr. Gambo Aliyu, this was done to support efforts geared towards preventing new HIV infections using information that was accurate in order to identify clearly where new infections are occurring and among which population group.
It is noteworthy to state that data from the 2018 Nigeria AIDS Indicator Impact Survey (NAIIS), which estimated HIV prevalence at 1.4 per cent, supplied most of the information on population size and characteristics used for the study. The key population (KP) size, prevalence rate for key populations and the number of new infections by states spread were estimated from the recent KP study.
The IPM model disaggregates the population by factors known to be associated with HIV acquisition, including sex, marital status, geographic location, male circumcision status, ART status and key risk behaviours. It is a method that uses results from trials or observational studies to develop initial estimates of incidence by population group and then applies a Bayesian framework to estimate the distribution of new infections that best matches the data and official estimates of the total number of new adult infections.
Most of the information on population size and characteristics was drawn from 2018 NAIIS population size and prevalence estimates for key populations were from the recent populations study. The model was calibrated to the number of new infections by states in 2020 as estimated by the national HIV estimate team.
Findings of the study on patterns of new HIV infections estimated that the largest number of new infections in the adult population is estimated to occur among Never Married Females and Never Married Males (young people). The next largest number of new infections occurs among Female Sex Workers (FSM) and Men who have Sex with Men (MSM).
According to the study, these four population groups account for about 91 per cent of all new infections among adults in Nigeria. Key populations (FSW, MSM and PWID), which represent less than two percent of the total population, account for about 11 percent of new infections.
The study listed how to reduce transmission: increase condom use with casual partners; the 35.3 per cent condom use at last sex with last non-regular partner should be increased with focused condom marketing and/or expanded access; increased HIV testing services; and improved treatment cascade would reduce HIV spread.
That is not all. Child infections due to mother-to-child transmission represent the second-largest source of new infections, accounting for 22 per cent of all new infections. In many states, child infections account for an even larger proportion – up to 50 per cent.
Among other things, findings have shown further that the distribution of new infections varies by state. In Nigeria, 20,000 new child infections take place yearly. Coverage of PMTCT services is low – only 44 per cent.
Main obstacle may be that only about 60 per cent of pregnant women received antenatal care from a skilled provider. Efforts are needed to identify high risk women to motivate them to attend ANC and get tested; while more needs to be done to expand PMTCT services beyond health facilities into the communities.
However, a large proportion of new infections generally occur among never married individuals or in sero-concordant negative couples; just as overall picture shows that young people and female sex workers appear to be playing an important role in the dynamics of the incidence. It was recommended that a study of formation and dissolution of partnerships among these groups may help in illuminating the dynamics.
Condom use at last sex is high, but consistent condom use is around 50 per cent. Another issue is that key populations get most of their information from radio and TV. The study suggested that expansion of PrEP (or pre-exposure prophylaxis or medicine people at risk for HIV take to prevent getting HIV from sex or injection drug use) could have an impact. It added that stigma and discrimination also limit access to services; while calling for programmes to address internalised stigma among key populations might be useful.
Also, mother-to-child transmission represents a large source of new infections nationally and is the largest source in several states. The study said most of women who attend antenatal care (ANC) get tested for HIV, but over 60 per cent of pregnant women do attend ANC. Increasing ANC attendance would benefit not only in reducing HIV transmission but also in the overall health of the child and the mother, the study concluded.
Overall picture is that the infection is decreasing among population, but increasing among never married population (largest source of new infections).
Also, the population is mostly young with a median age of 22 for females and 25 for men. The second largest source of new infections is newborns.
However, according to NACA boss, the study is another confirmation that Nigeria is willing to work hard and close the gaps as quickly as possible. He enthused that the findings of the study would further help the agency and partners redirect resources for maximum yields as Nigeria looks forward to attaining epidemic control with more targeted interventions.
“The policy implication is that efforts will be made to target the following population groups: the never married population, which is the largest source of new infections and is mostly between 17 and 34 for females and 19-31 for men. Special efforts are needed to be made to reach this population in schools, workplaces, gathering spots and through social media.
“For the new infections through newborns due to low coverage of PMTCT, efforts will be targeted at encouraging women to attend ANC especially in high prevalence states. Increased efforts especially for the highest risk FSW and MSM, which have shown that even though the population is small, prevalence remains high among sex workers and MSM in spite of high levels of reported condom use,” the NACA chief added.