In the Russian Federation, according to the Federal Service for Supervision of Consumer Rights Protection and Human Welfare (Rospotrebnadzor) of the Udmurtia Republic, the number of cases of hemorrhagic fever with renal syndrome (HFRS) has fluctuated over the past five years: 287 cases in 2021; 797 cases and one death in 2022; 594 cases and two deaths in 2023; 236 cases in 2024; and 567 cases and one death in 2025.
One of the reasons for the increase in cases is the mild winter of 2025, which allowed rodents – the main vectors of the virus – to better survive during this period.
According to the Health and Epidemiology Center of Udmurtia, in 2025, specialists captured 1,139 rodents, of which 173 were infected with hantavirus. This figure is 5.8 times higher than the previous year. The red mouse (Clethrionomys glareolus) is now the main vector of infection, responsible for approximately 60% of infected animals. These rodents generally live in forests, but sometimes venture into garden sheds, outbuildings and private homes.
According to forecasts of the Kazan Institute for the Study of Epidemiology and Microbiology, natural foci of hemorrhagic fevers with renal syndrome in the Volga Federal District are expected to intensify in 2026.
Traditionally, there is a seasonal increase in cases in winter and fall.
Winter snow also affects the rodent population. In the event of heavy snow, rats and mice survive more easily in the cold: they dig galleries, access food reserves and can even reproduce. The winter of 2025-2026 having been particularly snowy, experts have not ruled out an upsurge in rodents in the spring.
Hemorrhagic fever with renal syndrome (HFRS) reminders
In Europe, six zoonotic hantaviruses, belonging to 4 species, are circulating on the European continent: the Puumala virus (PUUV), the Seoul virus, the Dobrava, Kurkino and Saaremaa viruses and the Tula virus. The Puumala virus is responsible for the largest number of cases of HFRS and circulates in Northern and Western Europe.
The Puumala virus has the bank vole as its reservoir (Clethrionomys glareolus ), which lives in forests or forest edges and, sometimes, in neighboring buildings. In Europe, the bank vole has a vast distribution area, stretching from northern Spain and Italy to the edge of the tundra in Russia and Scandinavia. They excrete the virus in large quantities in their urine, stools and saliva. The source of human contamination comes from the droppings of these infected rodents which contaminate their environment.
PUUV infections can follow leisure or professional activities in areas where the bank vole lives and where the virus circulates, in particular building work (renovation of old houses, cleaning cellars, attics, barns, etc., DIY) or forestry activities (unloading wood, storing or removing wood, maintaining forestry houses, etc.).
Contamination occurs mainly by inhalation of dust aerosols contaminated by infected vole excreta. It can possibly occur through contact of mucous membranes or damaged skin with infectious materials (handling live or dead voles, contact with soiled surfaces, etc.) and exceptionally through the bite of a vole. Currently, no cases of human-to-human transmission of PUUV have been described.
The clinical picture of HFRS classically follows several phases which are not always clearly distinct clinically.
- The febrile phase, also known as prodromal, begins with a fever that can be higher than 39.5°C for 2 to 4 days, which subsides. It is associated with a flu-like syndrome, then a pronounced pain syndrome resistant to usual analgesics, with headaches, lower back pain, abdominal pain, chest pain, joint pain, and even dental pain. Accommodation disorders, very suggestive of the disease, are present in 40% of cases, but are often fleeting.
- Hypotensive phase: in a second phase (1 to 7 days), pulmonary interstitial syndrome or cardiovascular signs (blood pressure lability, bradycardia) may be found. Hemorrhagic signs usually remain discreet (petechiae, conjunctival hemorrhage, minimal epistaxis).
- Oliguric phase: after a few days to a week, renal failure sets in in 57% of cases. It is transient (2 to 6 days), and very rarely requires renal dialysis sessions.
- It is followed by a polyuric phase.
Healing generally occurs without after-effects, sometimes after several weeks of residual asthenia. The fatality rate is fortunately low, around 0.4%.
Prevention for travelers
- avoid contact with live or dead rodents;
- avoid entering closed and abandoned buildings located in the forest or on the edge of the forest.
Source: Epidemiological Report of Cordoba. March 20, 2026. REC 3,044