Kazan medical journalKazan medical journal0368-48142587-9359Eco-Vector8046610.17816/kazmj80466Research ArticleTo the clinic for undulating feverKhnyuninI. D.info@eco-vector.com15031932322-31711791809202118092021Copyright © 2021, Eco-Vector2021<p>Under the name of the undulating fever (Febris undulans), a kind of disease is described, characterized by prolonged fever lasting for several months and even, in some cases, more than a year, and the febrile periods are followed by periods of complete or relative apyrexia.</p>Kazan Medical archiveКазанский медицинский архив