Tracing the spread of HIV back to its source


Express June 23, 2010

Safety measures need to be strictly implemented to control the transmission of the HIV infection in Pakistan through migrant labourers who contract the virus from sex workers abroad, urges a medical study.

In a research paper, “Evidence for a ‘Founder Effect’ among HIV-infected Injection Drug Users (IDUs) in Pakistan” published in Bio Med Central Infectious Diseases 2010, a team of doctors, comprising two Pakistani experts from Aga Khan University Hospital and the University of Karachi and two Hawaii-based American doctors, further researched the spread of HIV in a group of people to find out whether they had obtained the virus from a single source.

The research article also reported that the HIV subtype ‘A’ is the most prevalent epidemic in IDU communities in Karachi. After obtaining informed consent, three millilitres of blood was collected from a sample of 26 men from Karachi, of an average age of 24, who were previously diagnosed positive for HIV. These 26 men had been infected with HIV because of injected drug use.

After extracting DNA from their blood samples and testing them, the HIV gene from the 26 IDUs revealed highly congruent topologies. “The HIV-1 strains from Pakistan clustered closely with HIV-1 subtype ‘A’ sequences from Senegal and Uganda,” the study revealed. These strains are unlike the ones found in neighbouring India, which validated the study’s hypothesis of the founder effect being the identified pattern of the spread of the virus.

The founder effect refers to the creation of a group through a single person or element. “The strains circulating amongst the selected community of IDUs in Karachi are most likely a consequence of a single-source infection,” the study explained. They claimed that the close phylogenetic clustering and strong identity among the HIV sequences indicates a “founder effect” of HIV in this community of IDUs. “The HIV infection most likely was transmitted to the entire group through the exchange of contaminated needles.”

The medical experts indicate that the group of IDUs were infected after one of them came in contact with commercial sex workers in the Middle East. “[One of] the study subjects [...] previously reported to have had contact with commercial sex workers during a prolonged stay in Sharjah, United Arab Emirates. During the early 1990s, the subject in question was deported from the UAE after being tested positive for HIV in Sharjah, after which he developed a habit of injecting drugs,” according to the research article.

The rest of the IDUs were diagnosed positive for HIV in the year 2000 and later, which shows they were infected by the deported subject. “The patient could be a possible source of infection in this community,” the experts said.

Therefore, the study recommended that to control HIV transmission in the country, a structured programme to screen and educate Pakistani migrant workers regarding sexually transmitted infections is needed. “With constant human traffic across borders from Middle East, Afghanistan, and India, clear-cut policies on HIV prevention across borders are urgently warranted,” the researchers urged.

Published in The Express Tribune, June 24th, 2010.

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