40 Years Since Bulgaria’s First HIV Case: How the Virus Has Evolved and Is There a Unique Bulgarian Strain?

December 1 marks exactly 40 years since the first HIV-positive Bulgarian was registered. The second case involved a sailor. Both individuals are still alive. Such long-term control over the HIV virus is extremely rare worldwide, and in Bulgaria, these two cases stand out. How has HIV evolved over this time, and is there a uniquely Bulgarian strain of the virus?

It was back in 1985. The world was already coming to terms with a severe and deadly epidemic, and the case in Pleven was not unexpected.

Prof. Radka Argirova, virologist: "The first recorded case was not a Bulgarian citizen. He was a Nigerian student. He passed away literally within two days."

To prevent the epidemic from entering the country, Bulgarian authorities began mandatory testing for all arrivals from abroad – including foreigners, sailors, and international drivers.

Prof. Radka Argirova, virologist: "The first Bulgarian patient was one of the sailors from the Black Sea Fleet in Burgas. According to him, he had been infected at least two years earlier."

Mandatory testing also covered other high-risk groups, such as patients with haemophilia, due to their frequent need for blood transfusions.

Prof. Radka Argirova, virologist: "Haemophiliacs are a very high-risk group, and at the time we identified 10 cases among our haemophilia patients."

Over more than 40 years of circulation in the human population and under the pressure of several generations of antiretroviral drugs, the HIV virus has not significantly changed.

Assoc. Prof. Ivaylo Alexiev, Head of the National HIV Reference Laboratory: "The virus does not become more aggressive. It always tends to stay in its wild type. The mutations weaken it, but help it to escape the drugs."

Although it tends to revert towards its wild type, the virus accumulates changes that can be seen as characteristic of specific populations.

Assoc. Prof. Ivaylo Alexiev, Head of the National HIV Reference Laboratory: "There are unique variants found in the country. These are called circulating recombinant forms – which occur when a person is infected with more than one subtype."

These forms demonstrate that the first infected individuals introduced viruses from around the world into Bulgaria. Remarkably, despite highly effective therapies that practically eliminate the risk of transmission, the country still records new infections – 300 cases this year alone.