Analyzes of two major domestic surveys in KwaZulu-Natal, South Africa, are shedding light on the dynamics of HIV transmission in the South African province that is hardest hit by the HIV / AIDS pandemic. Adolescents and young women contract HIV from older men, with a large margin in these age groups, while older people generally contract HIV from women in their age group. Men and women who migrate only fifty miles from home are more likely to become positive than those who remain in their community.
The two recently published studies, each using data from large household surveys in two different areas of KwaZulu-Natal. Migrations and disparate-age relationships have already been identified as factors driving the HIV epidemic in southern Africa, but these analyzes have been thoroughly sophisticated in order to clarify and reinforce evidence of how these factors act.
Age intervals between sexual partners - study
The first study, by Tulio de Oliveira, Ayesha Kharsany and colleagues, is published online before the HIV Lancet. The data come from a random sample, for the HIV test.
The researchers used phylogenetic analysis to identify the transmission links - in other words, groups of individuals who carried strains of HIV samples genetically similar and probably contracted HIV each other. Phylogenetic analysis showed estimates were as closely related to samples of viral strain of HIV in different individuals are compared with samples of HIV.
Of note, subjects who were well adherent to treatment and had a low viral load were not included in the phylogenetic analysis because the technique was still not completely reliable, excluding individuals with viral loads below 1000 copies / ml . In fact, this has the advantage of excluding people under treatment who are not likely to transmit HIV - the sample for phylogenetic analysis is skewed to people with recent infections, many of them undiagnosed.
A total of 9812 individuals participated in the study, of which 3969 were HIV-positive. Of these, 1589 had a viral load with more than 1000 copies / ml and provided blood samples that were sequenced successfully for phylogenetic analysis.
Four hundred and sixty-nine of these samples were pooled into 202 transmission groups, of which ninety subgroups included at least one woman and one man. These ninety groups were then analyzed at even greater depth.
Age intervals between sexual partners - the main conclusions
Ninety groupings were possible 188 pairings between men and women. A comparison of all possible pairs in age and sex categories identified two particular patterns.
First, twenty percent of the pairings were between men aged 25 to 40 years and women aged 15-25. Second, thirty-one percent of pairings were between men and women who were both aged between 25-40.
In other words, men aged 25-40 are the main source of HIV _contração_ in adolescents and young women.
Many of these men probably contracted the HIV infection of women aged 25 40 the years, the group with the highest HIV prevalence.
Over time, when the current group of adolescent girls and young women reach their thirties, they will have become the next group of women with high HIV prevalence and likely to perpetuate the cycle of HIV transmission for men in their thirties - which will infect the next cohort of adolescent girls and young women. (See the newspaper graph paper illustrating the transmission cycle).
Age differences between men and women in transmission clusters were large for younger women, but not for older women. Women aged 15-20 had male partners, an average of 11,5 years older; women aged 21-25 had 7,0 partners years older; women aged 26-30 had 1,5 partners years older; women aged 31-35 had 1,7 partners years older.
Of men aged 25-40, which were linked to a younger woman, 40% were also associated with a woman in her own age group.
People that were broadcast groups were often unaware of their infection, not taking treatment and had a high viral load.
internal migration - study
Labor migration is another key issue behind the HIV epidemic in South Africa, with a major impact on sexual partnerships between men and women. The second study, by Adrian Dobra, Frank Tanser and colleagues is published in the January issue of AIDS. Data from a longitudinal cohort of all households in a predominantly rural area within the Umkhanyakude district of KwaZulu-Natal.
The community is characterized by frequent migration to other parts of South Africa, marital low rates, multiple sexual partners and high rates desoropositividade positive for HIV that have not been diagnosed.
All households were visited annually (between 2004 and 2014) and the researchers interviewed and tested for HIV all household members over the age of 15 years of age who agreed to participate. Information on migration, which have been carefully recorded everywhere, noting when and where people migrated and from which region to that region. When members of the household were absent, the researchers asked family members and friends about their whereabouts.
The analysis focuses on 17.743 individuals who were tested for HIV twice or more as part of the study and can therefore analyze the relationship between HIV infections and migration.
internal migration - the main conclusions
Within the cohort analyzed, about one in five men and women in their twenties migrated at least once and usually for periods between 8 and 24 months. A quarter of all migrations were to places within a range of 100 km and the main destinations of these migrations were:
- Richards Bay (the 55km away)
- Durban (205km) and
- Johannesburg / Pretoria (473km).
Migration to nearby destinations were associated with an increased risk, especially for men:
- Men who migrated from 40km in one year had one 50% increased risk of acquiring HIV (hazard ratio 1,5).
- Men who migrated around 169km in one year had a 75% higher risk.
- Men who went from 44% of their time away from the community of origin would run a 50% higher risk of contracting HIV.
Risk for women was associated with the more migration and more time than men:
- Women who migrated 109km in one year had a 50% higher risk of contracting HIV.
- Women who migrated 652km had a 75% higher risk.
- Women who spent more than 90% of their time away from the community at home had a 50% higher risk.
"Mean migratory distances per year and increased periods of out-of-community living represent in rural study areas the major risk factors for HIV acquisition, such as increased numbers of sexual partners, increased likelihood of sexual behavior risk, family withdrawal, friends, community and social norms, increased vulnerability, or lower socioeconomic status, "say the authors.
In 21 International AIDS Conference (AIDS 2016) in Durban this yearFrank Tanser - one of the authors of the study - said that phylogenetic analyzes done in this district also highlighted the importance of migration. A number of new infections throughout the local area can be linked back to individuals living in 'hot spot' communities, adjacent to the highway.
Especially as migrants are often diagnosed late and have difficulty engaging with and Retension on health care, the researchers say HIV testing and treatment services in South Africa need to be better tailored to the needs of migrants.
Originally posted in 14 for December of 2016 in Migration and age differences between male and female partners fueling the HIV epidemic in South Africa
Translated, revised, edited by Claudio Souza in 17 December 2016.
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