Reactive markers of HIV, hepatitis B, hepatitis C and syphilis among people who use drugs in Sofia, Bulgaria: a cross-sectional bio-behavioural survey
A 2024 cross-sectional survey in Sofia, Bulgaria, reveals that two-thirds of people who use drugs carry at least one reactive marker for HIV, hepatitis B, hepatitis C, or syphilis, with injection history and age being the strongest correlates for high hepatitis C and HIV prevalence, highlighting the need for integrated testing and treatment services.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
In the crowded streets of Sofia, Bulgaria, a hidden health crisis plays out among people who use drugs. For decades, public health experts have known that sharing needles to inject drugs is a fast track to serious infections. Two of the most dangerous are HIV, which attacks the immune system, and hepatitis C, a virus that damages the liver. These viruses travel easily through blood, and when a needle is shared, even a tiny drop of infected blood can pass the disease from one person to another. While these infections can also spread through sexual contact, the risk skyrockets when people inject drugs together. In many parts of the world, the rate of these infections among people who inject drugs is far higher than in the general population. Understanding exactly how widespread these infections are in a specific city, and who is most at risk, is the only way to design services that actually work to stop the spread and save lives.
A team of researchers recently set out to map this landscape in Sofia. They did not sit in an office waiting for people to come to a clinic; instead, they went out to the places where people who use drugs gather. Working with a local non-profit organization, they approached 480 adults who had used illicit drugs in the month before the study. The researchers asked them detailed questions about their lives, their drug use, and their housing, and then collected a small drop of blood from each person. This blood was tested on the spot with rapid tests to see if it contained markers for HIV, hepatitis B, hepatitis C, and syphilis. The goal was not just to count infections, but to understand the story behind the numbers: who is carrying these viruses, how long they have likely been carrying them, and what factors in their daily lives put them at risk.
The results revealed a heavy burden of infection. Two out of every three people in the study carried a reactive marker for at least one of these blood-borne infections. The most common finding was hepatitis C. About 64 percent of all participants showed signs of having been exposed to the virus at some point in their lives. However, the story changed dramatically when the researchers looked at who had ever injected drugs versus those who had not. Among the people who had injected drugs, nearly 90 percent had been exposed to hepatitis C. In contrast, only about 19 percent of those who used drugs but never injected them showed signs of the virus. This stark difference confirmed that for hepatitis C, the act of injecting is the primary driver of infection in this community.
HIV told a different, though still serious, story. About 13 percent of all participants tested positive for HIV antibodies. Again, the risk was much higher for those who had injected drugs, with 17 percent testing positive, compared to just 5 percent of non-injectors. What made the HIV data particularly striking was how it did not follow the same pattern as hepatitis C. While hepatitis C infections piled up steadily as people got older and spent more years injecting, the rate of HIV did not rise with age in the same way. This suggests that hepatitis C has been circulating in this group for a very long time, accumulating over decades, whereas HIV may have entered the network more recently and spread in a different pattern. The researchers also found that people who were currently homeless or did not have a stable place to live were significantly more likely to have HIV, pointing to the deep connection between housing instability and the risk of infection.
The study also shed light on other infections. Syphilis and hepatitis B were found in only a small number of people, and unlike HIV and hepatitis C, their presence did not seem to be linked to whether a person had injected drugs. Instead, syphilis was more common among women, suggesting it spreads primarily through sexual contact in this group rather than through needles. This distinction is crucial because it means that a single approach to prevention cannot solve all the problems; different strategies are needed for different viruses.
Perhaps the most important finding was about the overlap between HIV and hepatitis C. Of the people who tested positive for HIV, 87 percent also tested positive for hepatitis C. This high level of co-infection means that treating these patients requires a unified approach. Separating services for HIV and hepatitis would be inefficient and would likely miss many people who need help. The researchers noted that while the rapid tests showed who had been exposed to hepatitis C, they could not tell who currently had an active, infectious virus. About a quarter of people who get hepatitis C clear it on their own, and others may have been cured by treatment but still show antibodies. Therefore, the next step for Sofia is to perform more detailed testing to find out exactly how many people need immediate medical treatment.
The study also highlighted a gap between what is available and what is happening on the ground. Almost everyone in the study said they could get new, sterile needles whenever they needed them. Yet, a significant number still reported using needles that had been used by someone else. This suggests that the problem is not a lack of equipment, but rather the difficult circumstances in which people use drugs. Factors like police presence, the urgency of withdrawal, or the lack of a safe place to use drugs can force people to share equipment even when clean needles are nearby. The researchers concluded that to truly protect this population, services must be integrated, housing must be addressed, and the focus must shift from simply distributing needles to ensuring people have the safety and stability needed to use them correctly. The data paints a clear picture of a community carrying a heavy load of preventable diseases, one that can only be lifted through coordinated, compassionate, and integrated care.
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