Bulgarian Lev, the first known known case of a vaccine-derived strain of Listeria monocytogenes, was reported in Bulgarian medical authorities on Saturday.
The Bulgarian health ministry said the case was the first case of vaccine-induced Listeriosis in Bulgaria, adding that it was still in the early stages of testing.
Lev, a 39-year-old man, died after contracting the infection at a hotel in Bulgaria’s capital, Sofia, on Thursday.
The case was identified as Lev Nenchev, a resident of the city of Veliko-Sevastopol, in the country’s south.
“We have received reports of a serious case of L. monocyticum infection in a patient in Sofia,” the ministry said in a statement.
“Based on our experience and clinical knowledge, we believe that the patient may have contracted the vaccine-related illness in the hotel.”
The Bulgarian Health Ministry said that Lev was taken to the city hospital for an evaluation.
Lev was one of the first documented cases of L-cytovirus infection in the European Union, which has been battling the disease for several months.
According to the WHO, the infection is primarily a mild disease with symptoms similar to that of seasonal flu, with only mild symptoms.
It can be fatal if left untreated.
According the Bulgarian Ministry of Health, the number of confirmed cases of the virus has reached 6,724.
The World Health Organization (WHO) estimates that 1.3 million people in Bulgaria have contracted L. serovarib in 2015, and an additional 300,000 are at risk.
The European Food Safety Authority has warned that the risk of a resurgence of the infection remains high.