Iran province logs a six-year decline in Crimean-Congo fever cases
A surveillance analysis of Sistan and Baluchestan finds confirmed and probable cases falling from a 2019 peak, with an 11% fatality rate and a clear winter clustering.
Reported Crimean-Congo haemorrhagic fever cases in Iran's Sistan and Baluchestan Province fell over six years to 2024, according to a surveillance analysis in the Eastern Mediterranean Health Journal, the WHO Regional Office for the Eastern Mediterranean's peer-reviewed journal [s1].
What the analysis found
The study examined suspected cases recorded from 2018 to 2024, drawn from the Communicable Disease Center of Zahedan University of Medical Sciences [s1]. Of 433 registered suspected cases over the period, 91 were laboratory-confirmed and 16 were classified as probable [s1]. The fatality rate among cases was 11% [s1].
The trend was downward. The highest annual count came in 2019, with 167 cases, and the lowest in 2024, with 15 [s1]. The authors describe this as a decreasing trend across the province [s1].
Cases also clustered by season. The analysis reports significantly more cases during the winter months, with a p-value below 0.001 [s1].
The ratio between the figures is worth noting: 91 confirmed and 16 probable cases out of 433 registered as suspected means most suspected cases were not ultimately confirmed as Crimean-Congo haemorrhagic fever [s1]. That is expected for a disease whose early symptoms overlap with many other febrile illnesses, and it is why laboratory confirmation, rather than the raw count of suspected cases, is the figure that carries the surveillance signal [s1].
What the disease is
Crimean-Congo haemorrhagic fever is a widespread disease caused by a tick-borne virus, and it can cause severe viral haemorrhagic fever outbreaks [s2]. The World Health Organization puts the case fatality rate at 10 to 40% — a range that sits above the 11% recorded in this provincial dataset [s1][s2]. The virus is transmitted to people primarily from ticks and livestock animals, and human-to-human transmission can occur through close contact with the blood, secretions or other bodily fluids of an infected person [s2].
The hosts of the virus include a wide range of wild and domestic animals, among them cattle, sheep and goats [s2]. The disease is endemic in Africa, the Balkans, the Middle East and parts of Asia, following the geographical limit of its principal tick vector [s2]. There is no vaccine available for either people or animals [s2]. Those facts explain why surveillance of the kind this study reports is the main line of defence: without a vaccine, detection and case management are what limit harm.
Why the pattern matters
Because human infection follows contact with infected ticks or with the blood and tissues of infected animals, case counts in any one district reflect a mix of animal reservoirs, tick activity and human exposure through livestock handling and slaughter, rather than person-to-person spread across the general population [s1][s2]. Sistan and Baluchestan, in Iran's south-east, is a livestock-raising region, and surveillance data of this kind are the primary way health authorities detect where and when exposure concentrates.
The winter clustering the study identifies is the sort of pattern that can guide the timing of prevention messaging and case-readiness in clinics [s1]. It runs against the intuition that a tick-borne disease should peak in summer, and the authors flag the winter months specifically as the period to strengthen prevention, diagnosis and treatment [s1].
The limits of the picture
The figures are for a single province and are built from suspected cases reported into one university's communicable-disease system, then narrowed to laboratory-confirmed and probable classifications [s1]. Surveillance counts of this kind are shaped by how many people present for testing and by laboratory capacity, so a falling count can reflect changes in reporting as well as changes in true incidence.
The study does not claim to resolve that question. It is a descriptive surveillance study, not an evaluation of any specific control programme, and it draws no conclusion about why the count declined [s1]. That leaves the driver of the six-year fall — a genuine reduction in exposure, shifts in testing, or both — as the open question a follow-up would need to address. What the data support is narrower and still useful: in one endemic, livestock-raising province, confirmed cases have trended down and concentrate in winter, and with no vaccine available the value of that finding is entirely in what it tells clinicians and animal-health services about when to be ready [s1][s2].
Sources
- [s1] "Six-year trend of Crimean-Congo haemorrhagic fever cases in Islamic Republic of Iran," Eastern Mediterranean Health Journal, 2 August 2026. https://doi.org/10.26719/2026.32.7.446
- [s2] "Crimean-Congo haemorrhagic fever," fact sheet, World Health Organization, 20 February 2025. https://www.who.int/news-room/fact-sheets/detail/crimean-congo-haemorrhagic-fever
Sources
- Six-year trend of Crimean-Congo haemorrhagic fever cases in Islamic Republic of Iran — Eastern Mediterranean Health Journal (WHO EMRO) , August 2, 2026
- Crimean-Congo haemorrhagic fever (fact sheet) — World Health Organization , February 20, 2025
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