Because heterosexual transmission of HIV is responsible for a large percentage of HIV infections, there is an expected risk that an HIV positive person will infect a negative partner if they have unprotected sex. But what continues to baffle many including medical personnel is the increasing incidence of discordance in relationships; that is, a situations where a positive person does not infect a partner despite the odds. This peculiarity looks worrisome especially as researchers are yet to come up with an explanation for this situation, although a couple of indicators have been suggested for this occurrence.
Serodiscordance is a situation where a couple’s sero (blood) status is not compatible. This scenario began to emerge as the incidence of a wife testing positive and husband negative was seen by health practitioners in HIV work.
“The discordant rate is increasing. It is as high as 45 per cent in PMTCT clinic,” says Professor Isaac Adewole, a gynaecologist at the University College Hospital, Ibadan. In his experience at the Prevention of Mother to Child Transmission of HIV (PMTCT) at UCH, professor Adewole recounts that many homes have been broken as a result of this discovery.
“Medicine is meant for happiness and not for breaking homes,” he says. “We have experienced several cases of sero-discordance, and we are often faced with the challenge not to cause unhappiness or break homes, because most of the husbands accuse their wives of unfaithfulness and send them out.”
A colleague concurred with the professor’s findings, saying: “In about 20% of the mothers that I have managed, their spouses were HIV negative,” according Dr. Ebun Adejuyigbe Department of Peadiatrics, Obafemi Awolowo University, Ile-Ife, Nigeria.
Unfaithfulness, which is the most common reason one partner may test HIV positive while the other remains negative, does not completely explain the medical possibilities. Professor of Gynaecology, Dr Sagay, said that despite ongoing research, the causes are still largely unknown. Some causes have been traced to the interrelation of the several factors ranging from transmission rates due to anatomical structure of male and female genitals where men are less vulnerable to contracting the virus than women; virulence of HIV strains; circumcision factors and level of sexual experience at the point of marriage.
The biological or anatomical structure of the female genital is such that an HIV positive man can easily transmit HIV to the woman during unprotected sex, even just at first meeting, while a woman who is positive may not transmit virus to the man. (The surface area of the vagina is wider and contains more body fluid.)Thus, transmission rate is twice as high from a man to a woman than from a woman to a man. As a result, the positive wife might not easily transfer the virus to her husband even during several intercourse periods, if she had been infected before or during marriage.
Apart from this, male circumcision is another factor that may prevent the man from the infection. Men who are circumcised are more unlikely to be infected than men who are not.” Circumcision plays a major role. Men who are circumcised have more difficulty contracting HIV through unprotected sex than men who are not,” Prof Sagay says. This discovery has led communities that don’t circumcise their males to embark on circumcision as an HIV prevention strategy.
The virulence of HIV strain an HIV positive person carries also plays a role in serodiscordance. If a woman acquired the infection either before marriage, the virulence of the HIV strain determines the transmission rate. Researchers have established that certain strains are more virulent and are therefore more efficiently transmitted than others. If, for example, the wife has the HIV that has a less tricky recombinant character the chances of infecting the man is greatly reduced. She may have unprotected sex several times and the virus does not cross over to the man.
Sexual experience of the woman at the time of marriage is another factor. Women are more vulnerable to HIV due to reasons ranging from biological to social economic, cultural and religious factors. Young women are likely to have sexual relations with older men with more advanced sexual experience than their male counterparts, before marriage. As a result, by the time she decides to get married, she might have acquired the infection, unknown to her.
An important factor to be considered in discordance also is length of cohabitation as married couples. In most of the hospital case studies, the longest time of living together is so far 2 years. It is unclear whether the longer the cohabitation period, the lesser rates of discordance will be.