Crimean-Congo haemorrhagic fever (CCHF) is a pathogenic and often fatal arboviral disease with a distribution spanning large areas of Africa, Europe and Asia. The causative agent is a negative-sense single-stranded RNA virus classified within the Nairovirus genus of the Bunyaviridae family. Cases of CCHF have been officially recorded in Kazakhstan since the disease was first officially reported in modern medicine. Serological surveillance of human and animal populations provide evidence that the virus was perpetually circulating in a local enzoonotic cycle involving mammals, ticks and humans in the southern regions of the country. Most cases of human disease were associated with agricultural professions such as farming, shepherding and fruit-picking; the typical route of infection was via tick-bite although several cases of contact transmission associated with caring for sick patients have been documented. In total, 704 confirmed human cases of CCHF have been registered in Kazakhstan from 1948-2013 with an overall case fatality rate of 14.8% for cases with a documented outcome. The southern regions of Kazakhstan should be considered endemic for CCHF with cases reported from these territories on an annual basis. Modern diagnostic technologies allow for rapid clinical diagnosis and for surveillance studies to monitor for potential expansion in known risk areas.

Omsk haemorrhagic fever virus (OHFV) is the agent leading to Omsk haemorrhagic fever (OHF), a viral disease currently only known in Western Siberia in Russia. The symptoms include fever, headache, nausea, muscle pain, cough and haemorrhages. The transmission cycle of OHFV is complex. Tick bites or contact with infected small mammals are the main source of infection. The Republic of Kazakhstan is adjacent to the endemic areas of OHFV in Russia and febrile diseases with haemorrhages occur throughout the country—often with unclear aetiology. In this study, we examined human cerebrospinal fluid samples of patients with suspected meningitis or meningoencephalitis with unknown origins for the presence of OHFV RNA. Further, reservoir hosts such as rodents and ticks from four Kazakhstan regions were screened for OHFV RNA to clarify if this virus could be the causative agent for many undiagnosed cases of febrile diseases in humans in Kazakhstan. Out of 130 cerebrospinal fluid samples, two patients (1.53%) originating from Almaty city were positive for OHFV RNA. Screening of tick samples revealed positive pools from different areas in the Akmola region. Of the caught rodents, 1.1% out of 621 were positive for OHFV at four trapping areas from the West Kazakhstan region. In this paper, we present a broad investigation of the spread of OHFV in Kazakhstan in human cerebrospinal fluid samples, rodents and ticks. Our study shows for the first time that OHFV can not only be found in the area of Western Siberia in Russia, but can also be detected up to 1.600 km away in the Almaty region in patients and natural foci.

Orthohantaviruses are zoonotic pathogens that play a significant role in public health. These viruses can cause haemorrhagic fever with renal syndrome in Eurasia. In the Republic of Kazakhstan, the first human cases were registered in the year 2000 in the West Kazakhstan region. Small mammals can be reservoirs of orthohantaviruses. Previous studies showed orthohantavirus antigens in wild-living small mammals in four districts of West Kazakhstan. Clinical studies suggested that there might be further regions with human orthohantavirus infections in Kazakhstan, but genetic data of orthohantaviruses in natural foci are limited. The aim of this study was to investigate small mammals for the presence of orthohantaviruses by molecular biological methods and to provide a phylogenetic characterization of the circulating strains in Kazakhstan. Small mammals were trapped at 19 sites in West Kazakhstan, four in Almaty region and at seven sites around Almaty city during all seasons of 2018 and 2019. Lung tissues of small mammals were homogenized and RNA was extracted. Orthohantavirus RT-PCR assays were applied for detection of partial S and L segment sequences. Results were compared to published fragments. In total, 621 small mammals from 11 species were analysed. Among the collected small mammals, 2.4% tested positive for orthohantavirus RNA, one sample from West Kazakhstan and 14 samples from Almaty region. None of the rodents caught in Almaty city were infected. Sequencing parts of the small (S) and large (L) segments specified Tula virus (TULV) in these two regions. Our data show that geographical distribution of TULV is more extended as previously thought. The detected sequences were found to be split in two distinct genetic clusters of TULV in West Kazakhstan and Almaty region. TULV was detected in the common vole (Microtus arvalis) and for the first time in two individuals of the forest dormouse (Dryomys nitedula), interpreted as a spill-over infection in Kazakhstan.

Hemorrhagic fever with renal syndrome (HFRS) is a zoonotic disease associated with orthohantaviruses maintained in natural rodent hosts. This study assessed the detection and spatial distribution of hantavirus RNA among small mammals in the West Kazakhstan Region in 2025 and compared rodent surveillance findings with human HFRS occurrence. An observational cross-sectional analytical study was conducted in July and September 2025 in four districts. A total of 343 small mammals were captured and morphologically identified. Lung tissue samples from 329 animals collected in September were examined in 123 pooled testing units, whereas 14 animals collected in July were tested individually. Thus, 137 testing units representing 343 animals were evaluated by real-time and conventional RT-PCR. The minimum infection rate (MIR) was calculated as a descriptive minimum estimate, and a pooled-testing likelihood model was used to account for variation in testing-unit size. Hantavirus RNA was detected in 47/137 testing units, including 45 positive pooled units and two individually positive specimens. Based on 343 individual animals, the descriptive MIR was 13.7%. The model-based individual-level infection probability was estimated at 18.0% (95% profile-likelihood CI: 13.5–23.1%). Positive testing units were observed among the Ural field mouse (Apodemus uralensis), bank vole (Myodes glareolus), and common vole (Microtus arvalis). At the district level, the descriptive MIR ranged from 11.6% in Burlinsky to 19.0% in Chingirlauisky. Sampling sites overlapped spatially with settlements reporting human HFRS cases, including Utvinka, Daryinsk, and Rubezhinskoye; however, spatial coincidence does not establish direct transmission.

Hemorrhagic fever with renal syndrome (HFRS) is a zoonotic disease associated with orthohantaviruses maintained in natural rodent hosts. This study assessed the detection and spatial distribution of hantavirus RNA among small mammals in the West Kazakhstan Region in 2025 and compared rodent surveillance findings with human HFRS occurrence. An observational descriptive-analytical study was conducted in August–September 2025 in four districts. A total of 343 small mammals were captured and morphologically identified. Lung tissues were tested using 123 pooled testing units, while 14 specimens were tested individually during the same surveillance campaign. Thus, 137 testing units representing 343 animals were evaluated by real-time and conventional RT-PCR. The minimum infection rate (MIR) was calculated as a descriptive minimum estimate, and a pooled-testing likelihood model was used to account for variation in testing-unit size. Hantavirus RNA was detected in 47/137 testing units, including 45 positive pooled units and two individually positive specimens, corresponding to a descriptive MIR of 13.7%. The model-based individual-level infection probability was estimated at 18.0% (95% profile-likelihood CI: 13.5–23.1%). Positive testing units were observed among Apodemus uralensis, Myodes glareolus, and Microtus arvalis. At the district level, the descriptive MIR ranged from 11.6% in Burlinsky to 19.0% in Chingirlauisky. Sampling sites overlapped spatially with settlements reporting human HFRS cases, including Utvinka, Daryinsk, and Rubezhinskoye; however, spatial coincidence does not establish direct transmission.