Cracking the series of Transmission

  • September 19, 2017
  • 1:18 am
  • Sweekriti Nakhat
Epidemiology is the science which studies the modes of transmission of pathogenic agents, the causes of diseases, their impact on health, as well as the economical and the sociological consequences of outbreaks in populations.
Outbreaks are the result of a “three-link chain” like series of events called the “chain of transmission”.

Complete elimination of mother-to-child transmission of HIV seems achievable now..

While medical science has made big advances in the HIV/AIDS fight, it has failed to win the battle so far. But there is one bright spot. The complete elimination of mother-to-child transmission (MTCT) of the virus seems achievable. Currently, 5% of babies born to those who are HIV-positive get infected. Last December, the National AIDS Control Organisation (NACO) had given indications that it could bring that figure down to less than 2% by 2030. Worldwide, a transmission rate below 2% is considered elimination.

When there was a steep fall in her blood pressure ,Nayna (name changed), 28, was admitted to JJ Hospital in Mumbai . Even though her first child, a boy, had tested positive for HIV ,six months pregnant and HIV-positive, she had not registered herself at any health-care facility . “We counselled Nayna and her husband, also HIV+, until they realised the seriousness of the disease. She was started on medication immediately,” says Rupali Tople, counsellor at the hospital. “We promised her that were she to comply with our instructions, we would ensure that her second baby was HIV-negative.” In February, Nayna gave birth to a girl, who has tested negative since.

Key route of transmission

MTCT is the primary route of transmission of HIV among children. Babies are infected during pregnancy, labour, delivery or while breastfeeding. Without any intervention, the risk of transmission is 20-45%. But antiretroviral drugs and other strategies can bring it down considerably.

“India has now moved on to the most advanced regimen. With good drugs and thorough compliance, the viral load in a mother reduces drastically and thus helps control transmission to babies to a large extent,” says gynaecologist Dr. Rekha Daver, who is on NACO’s core committee for elimination of MTCT.

Earlier, Indian health providers offered ‘single dose therapy’, which involved administering the antiretroviral drug, nevirapine, to pregnant HIV-positive women two hours before delivery and to newborns within 72 hours of birth.

In 2014, the country moved on to follow the World Health Organisation (WHO) recommended ‘multidrug therapy’, which is a combination of three drugs — tenofovir, lamivudine and efavirenz (TLE).
Affected women need to take it all their lives and nevirapine syrup for six weeks only for their babies. “Nevirapine is known to cause drug-resistant HIV in mothers. With the new regimen, we not only think about the baby but also the mother,” Dr. Daver explains.

In 2015, Cuba became the first country in the world to receive validation from WHO that it had eliminated mother-to-child transmission of HIV and syphilis, followed by Thailand and Belarus.

Among African countries, Uganda claims to be in the pre-elimination stage. “The enormous population in India makes it challenging for health-care workers to reach out to every pregnant woman. On the other hand, pregnant women too often delay registering for antenatal care,” says gynaecologist Dr. Ashok Anand of JJ Hospital. He says registering early is necessary to detect and eliminate MTCT.

However people like Nayna are lucky. According to NACO, only about 52.7% of pregnant mothers seek skilled care out of an estimated 27 million pregnancies in a year. An estimated 35,200 pregnancies occur in HIV-positive women and more than 10,300 infected babies are born annually, without any intervention.

Reducing risk

Women generally are advised to breastfeed only for six months until their babies can develop their own antibodies against a range of illnesses. But some doctors recommend that HIV-positive women should not breastfeed as their milk harbours the virus.

“For patients from underprivileged classes, replacing the nutrition for the baby without breastfeeding is difficult. But we do advise it to affording patients,” says the Mumbai-based gynaecologist Dr. Suchitra Pandit.

Dr. Pandit notes that many women also opt for caesarean section surgeries to reduce the risk further. During a baby’s journey through the vaginal passage, contact with abrasions, secretions and blood, which contain the virus, increases the risk of transmission.

A clinical trial conducted in Europe had shown that elective caesarean section and no breastfeeding limits the transmission.

But Dr. Daver says that multidrug therapy is usually adequate to drastically reduce a mother’s viral load. “If a virus does reach the baby, nevirapine does the rest of the work,” she says.