@article{:/content/10.2807/esm.10.06.00548-es, author = "Petrov, M and Hadjieva, N and Kantardjiev, T and Velinov, Tz and Bachvarova, A", title = "", journal = "", year = "", volume = "", number = "", eid = , pages = "", url = "https://www.eurosurveillance.org/content/10.2807/esm.10.06.00548-es", doi = "https://doi.org/" }