Risk of human infections with Crimean-Congo hemorrhagic fever virus in a South African rural community

Distinguishing host responses, extensive viral dissemination and long-term viral RNA persistence in domestic sheep experimentally infected with Crimean-Congo haemorrhagic fever virus Kosovo Hoti

Crimean-Congo haemorrhagic fever orthonairovirus (CCHFV) is a tick-borne, risk group 4 pathogen that often causes a severe haemorrhagic disease in humans (CCHF) with high case fatality rates. The virus is believed to be maintained in a tick-vertebrate-tick ecological cycle involving numerous wild and domestic animal species; however the biology of CCHFV infection in these animals remains poorly understood. Here, we experimentally infect domestic sheep with CCHFV Kosovo Hoti, a clinical isolate representing high pathogenicity to humans and increasingly utilized in current research. In the absence of prominent clinical signs, the infection leads to an acute viremia and coinciding viral shedding, fever and markers for potential impairment in liver and kidney functions. A number of host responses distinguish the subclinical infection in sheep versus fatal infection in humans. These include an early reduction of neutrophil recruitment and its chemoattractant, IL-8, in the blood stream of infected sheep, whereas neutrophil infiltration and elevated IL-8 are features of fatal CCHFV infections reported in immunodeficient mice and humans. Several inflammatory cytokines that correlate with poor disease outcomes in humans and have potential to cause vascular dysfunction, a primary hallmark of severe CCHF, are down-regulated or restricted from increasing in sheep. Of particular interest, the detection of CCHFV RNA (including full-length genome) in a variety of sheep tissues long after the acute phase of infection indicates a widespread viral dissemination in the host and suggests a potentially long-term persisting impact of CCHFV infection. These findings reveal previously unrecognized aspects of CCHFV biology in animals.

Transmission Dynamics of Crimean-Congo Haemorrhagic Fever Virus (CCHFV): Evidence of Circulation in Humans, Livestock, and Rodents in Diverse Ecologies in Kenya

Crimean-Congo haemorrhagic fever virus (CCHFV) is the causative agent of CCHF, a fatal viral haemorrhagic fever disease in humans. The maintenance of CCHFV in the ecosystem remains poorly understood. Certain tick species are considered as vectors and reservoirs of the virus. Diverse animals are suspected as amplifiers, with only scarce knowledge regarding rodents in virus epidemiology. In this study, serum samples from febrile patients, asymptomatic livestock (cattle, donkeys, sheep, and goats), and peridomestic rodents from Baringo (Marigat) and Kajiado (Nguruman) counties within the Kenyan Rift Valley were screened for acute CCHFV infection by RT-PCR and for CCHFV exposure by ELISA. RT-PCR was performed on all livestock samples in pools (5-7/pool by species and site) and in humans and rodents individually. CCHFV seropositivity was significantly higher in livestock (11.9%, 113/951) compared to rodents (6.5%, 6/93) and humans (5.9%, 29/493) (p = 0.001). Among the livestock, seropositivity was the highest in donkeys (31.4%, 16/51), followed by cattle (14.1%, 44/310), sheep (9.8%, 29/295) and goats (8.1%, 24/295). The presence of IgM antibodies against CCHFV was found in febrile patients suggesting acute or recent infection. CCHFV RNA was detected in four pooled sera samples from sheep (1.4%, 4/280) and four rodent tissues (0.83%, 4/480) showing up to 99% pairwise nucleotide identities among each other. Phylogenetic analyses of partial S segment sequences generated from these samples revealed a close relationship of 96-98% nucleotide identity to strains in the CCHFV Africa 3 lineage. The findings of this study suggest active unnoticed circulation of CCHFV in the study area and the involvement of livestock, rodents, and humans in the circulation of CCHFV in Kenya. The detection of CCHF viral RNA and antibodies against CCHFV in rodents suggests that they may participate in the viral transmission cycle.

Vaccine efficacy trials for Crimean-Congo haemorrhagic fever: Insights from modelling different epidemiological settings

BACKGROUND

Crimean-Congo haemorrhagic fever (CCHF) is a priority emerging pathogen for which a licensed vaccine is not yet available. We aim to assess the feasibility of conducting phase III vaccine efficacy trials and the role of varying transmission dynamics.

METHODS

We calibrate models of CCHF virus (CCHFV) transmission among livestock and spillover to humans in endemic areas in Afghanistan, Turkey and South Africa. We propose an individual randomised controlled trial targeted to high-risk population, and use the calibrated models to simulate trial cohorts to estimate the minimum necessary number of cases (trial endpoints) to analyse a vaccine with a minimum efficacy of 60%, under different conditions of sample size and follow-up time in the three selected settings.

RESULTS

A mean follow-up of 160,000 person-month (75,000-550,000) would be necessary to accrue the required 150 trial endpoints for a target vaccine efficacy of 60 % and clinically defined endpoint, in a setting like Herat, Afghanistan. For Turkey, the same would be achieved with a mean follow-up of 175,000 person-month (50,000-350,000). The results suggest that for South Africa the low endemic transmission levels will not permit achieving the necessary conditions for conducting this trial within a realistic follow-up time. In the scenario of CCHFV vaccine trial designed to capture infection as opposed to clinical case as a trial endpoint, the required person-months is reduced by 70 % to 80 % in Afghanistan and Turkey, and in South Africa, a trial becomes feasible for a large number of person-months of follow-up (>600,000). Increased expected vaccine efficacy > 60 % will reduce the required number of trial endpoints and thus the sample size and follow-time in phase III trials.

CONCLUSIONS

Underlying endemic transmission levels will play a central role in defining the feasibility of phase III vaccine efficacy trials. Endemic settings in Afghanistan and Turkey offer conditions under which such studies could feasibly be conducted.

Seroepidemiology of Crimean-Congo Haemorrhagic Fever among cattle in Cameroon: Implications from a One Health perspective

Background

Crimean-Congo Haemorrhagic Fever (CCHF) is a tick-borne viral zoonotic disease distributed across several continents and recognized as an ongoing health threat. In humans, the infection can progress to a severe disease with high fatality, raising public health concerns due to the limited prophylactic and therapeutic options available. Animal species, clinically unaffected by the virus, serve as viral reservoirs and amplifier hosts, and can be a valuable tool for surveillance. Little is known about the occurrence and prevalence of Crimean-Congo Haemorrhagic Fever Virus (CCHFV) in Cameroon. Knowledge on CCHFV exposure and the factors associated with its presence in sentinel species are a valuable resource to better understand transmission dynamics and assess local risks for zoonotic disease emergence.

Methods and findings

We conducted a CCHFV serological survey and risk factor analysis for animal level seropositivity in pastoral and dairy cattle in the North West Region (NWR) and the Vina Division (VD) of the Adamawa Region in Cameroon. Seroprevalence estimates were adjusted for sampling design-effects and test performance. In addition, explanatory multivariable logistic regression mixed-effects models were fit to estimate the effect of animal characteristics, husbandry practices, risk contacts and ecological features on the serological status of pastoral cattle. The overall seroprevalence was 56.0% (95% CI 53.5–58.6) and 6.7% (95% CI 2.6–16.1) among pastoral and dairy cattle, respectively. Animals going on transhumance had twice the odds of being seropositive (OR 2.0, 95% CI 1.1–3.8), indicating that animal movements could be implicated in disease expansion. From an ecological perspective, absolute humidity (OR 0.6, 95% CI 0.4–0.9) and shrub density (OR 2.1, 95% CI 1.4–3.2) were associated with seropositivity, which suggests an underlying viral dynamic connecting vertebrate host and ticks in a complex transmission network.

Conclusions

This study demonstrated high seroprevalence levels of CCHFV antibodies in cattle in Cameroon indicating a potential risk to human populations. However, current understanding of the underlying dynamics of CCHFV locally and the real risk for human populations is incomplete. Further studies designed using a One Health approach are required to improve local knowledge of the disease, host interactions and environmental risk factors. This information is crucial to better project the risks for human populations located in CCHFV-suitable ecological niches.

Crimean-Congo haemorrhagic fever poses an important threat for public health, particularly in endemic locations in Eurasia and parts of Africa. Despite its long-standing recognition, CCHF is considered a neglected disease, with sporadic official case reports and evidence of serological circulation in remote rural areas and less frequently, in peri-urban settings in sub-Saharan Africa. However, the drivers associated with its emergence and the spatial-temporal patterns linked to its circulation and spread are not well-understood. In this study, we identified a high proportion of cattle with CCHFV antibodies suggestive of high levels of viral circulation in the North West and the Adamawa Regions in Cameroon. In pastoral cattle, there was a positive relationship between going on transhumance, older age, higher shrub density and lower absolute humidity and CCHFV individual seropositivity. In contrast, non-indigenous breeds reported a lower risk of being seropositive. These results can be interpreted in connection to the underlying dynamics of CCHFV cycle and underline potential mechanisms linked to disease expansion. From a public health perspective, high levels of exposure to CCHFV in cattle highlight the possibility of unrecognized human infection and therefore, emphasize on the need to remain vigilant to possible disease risks for local groups involved in pastoralism and to dairy smallholders across the region.

Predictive Analytics of Cattle Host and Environmental and Micro-Climate Factors for Tick Distribution and Abundance at the Livestock-Wildlife Interface in the Lower Okavango Delta of Botswana

Tick distribution and abundance is influenced by several factors that include micro-climate and environmental and host factors. Contextual understanding of the role played by these factors is critical to guide control measures. The aim of this study was to determine the predictive value of these factors for changes in tick distribution and abundance at the livestock-wildlife interface of the lower Okavango Delta. A two-stage quota sampling design was adopted to select 30 clusters of seven cattle each for tick investigation. Tick investigation was done by lifting the tail to count the total number of ticks at the anno-vulva region during the four meteorological seasons of the year. Additional data were collected on ear tag number, location of origin, sex, age, body condition score (BCS), season of the year, stocking density, and Normalized Difference Vegetation Index values of source terrain. A random effects model was used to evaluate predictive value of the above for tick abundance. Additional mapping of tick distribution pattern in the abattoir catchment area was conducted using spatial autocorrelation and hot-spot analysis. Tick intensity of infection increased linearly from males to females (Z = 3.84, p < 0.001), decreased linearly from lower to higher BCS (Z = -4.11, p < 0.001), and increased linearly from cold-dry through dry to wet seasons (Z = 10.19, p < 0.001). Significant clustering of neighboring crushes on account of tick count was noted in the late-hot-dry season, with high tick count in crushes located along the seasonal flood plains and low tick counts in those located in the dry grasslands. It was concluded from this study that cattle tick abundance is influenced largely by season of the year and that the micro-climatic conditions brought about by the seasonal flooding of the delta have a decided effect on tick distribution during the driest of the seasons. Our study has, for the first time, profiled drivers of tick distribution and population growth in this unique ecosystem. This has the potential to benefit human and veterinary public health in the area through implementation of sustainable tick control strategies that are not heavily reliant on acaricides.

Risk factors associated with exposure to Crimean-Congo haemorrhagic fever virus in animal workers and cattle, and molecular detection in ticks, South Africa

Crimean-Congo haemorrhagic fever (CCHF) is a severe tick-borne viral zoonosis endemic to parts of Africa, Europe, the Middle East and Central Asia. Human cases are reported annually in South Africa, with a 25% case fatality rate since the first case was recognized in 1981. We investigated CCHF virus (CCHFV) seroprevalence and risk factors associated with infection in cattle and humans, and the presence of CCHFV in Hyalomma spp. ticks in central South Africa in 2017-18. CCHFV IgG seroprevalence was 74.2% (95%CI: 64.2-82.1%) in 700 cattle and 3.9% (95%CI: 2.6-5.8%) in 541 farm and wildlife workers. No veterinary personnel (117) or abattoir workers (382) were seropositive. The prevalence of CCHFV RNA was significantly higher in Hyalomma truncatum (1.6%) than in H. rufipes (0.2%) (P = 0.002). Seroprevalence in cattle increased with age and was greater in animals on which ticks were found. Seroprevalence in cattle also showed significant geographic variation. Seroprevalence in humans increased with age and was greater in workers who handled livestock for injection and collection of samples. Our findings support previous evidence of widespread high CCHFV seroprevalence in cattle and show significant occupational exposure amongst farm and wildlife workers. Our seroprevalence estimate suggests that CCHFV infections are five times more frequent than the 215 confirmed CCHF cases diagnosed in South Africa in the last four decades (1981-2019). With many cases undiagnosed, the potential seriousness of CCHF in people, and the lack of an effective vaccine or treatment, there is a need to improve public health awareness, prevention and disease control.

Epidemiology of Crimean-Congo Hemorrhagic Fever (CCHF) in Africa-Underestimated for Decades

Crimean-Congo hemorrhagic fever (CCHF) is endemic in Africa, but the epidemiology remains to be defined. Using a broad database search, we reviewed the literature to better define CCHF evidence in Africa. We used a One Health approach to define the impact of CCHF by reviewing case reports, human and animal serology, and records of CCHF virus (CCHFV) isolations (1956-mid-2020). In addition, published and unpublished collection data were used to estimate the geographic distribution of Hyalomma ticks and infection vectors. We implemented a previously proposed classification scheme for organizing countries into five categories by the level of evidence. From January 1, 1956 to July 25, 2020, 494 CCHF cases (115 lethal) were reported in Africa. Since 2000, nine countries (Kenya, Mali, Mozambique, Nigeria, Senegal, Sierra Leone, South Sudan, Sudan, and Tunisia) have reported their first CCHF cases. Nineteen countries reported CCHF cases and were assigned level 1 or level 2 based on maturity of their surveillance system. Thirty countries with evidence of CCHFV circulation in the absence of CCHF cases were assigned level 3 or level 4. Twelve countries for which no data were available were assigned level 5. The goal of this review is to inform international organizations, local governments, and healthcare professionals about shortcomings in CCHF surveillance in Africa to assist in a movement toward strengthening policy to improve CCHF surveillance.

Antiviral Therapy of Haemorrhagic Fevers and Arbovirus Infections

RNA viruses of the families Arena-, Bunya-, Filo-, Flavi-and Togaviridae cause illness in humans ranging from mild, non-specific febrile syndromes to fulminant, lethal haemorrhagic fever. They are transmitted from animals to humans and from human to human by arthropods, aerosols or contact with body fluids. Antiviral compounds, convalescent plasma and interferon inhibit many of these agents in vitro and in virus-infected animals. Drug or plasma treatment is now in use for several human diseases, and would probably be beneficial for a number of others for which there is only limited treatment experience. Success is linked to early diagnosis and initiation of therapy. Ribavirin is used to treat Lassa fever and haemorrhagic fever with renal syndrome, and would probably be effective for Crimean-Congo haemorrhagic fever and for all New World arenavirus diseases. The value of ribavirin in the early treatment of hantavirus pulmonary syndrome is under evaluation. Convalescent plasma is the therapy of choice for Argentine haemorrhagic fever, and would also probably be effective for other New World arenaviruses and some other infections if a safe supply of plasma could be maintained. Ribavirin and interferon-α have both shown protective efficacy in non-human primates infected with Rift Valley fever virus. No effective therapy has yet been identified for filovirus infections, but results in animal models are encouraging. More clinical research is urgently needed. Even if placebo-controlled drug trials cannot be performed, conscientious reports of the results of therapy in limited numbers of patients can still provide evidence of antiviral drug effects.

Nosocomial infections caused by Crimean-Congo haemorrhagic fever virus

Crimean-Congo haemorrhagic fever (CCHF) is an acute febrile illness, often accompanied by haemorrhagic manifestations, with a high case fatality rate (CFR). The causative agent is CCHF virus (CCHFV), and is transmitted to humans mainly through tick bites or exposure to blood or tissues of viraemic patients or livestock. Human-to-human transmission usually occurs in hospital settings, and healthcare workers (HCWs) are mainly affected. A review on nosocomial CCHFV infections was performed to elucidate the routes and circumstances of CCHFV transmission in hospital settings. From 1953 to 2016, 158 published cases of CCHFV nosocomial infection in 20 countries in Africa, Asia and Europe were found. Almost all cases were symptomatic (92.4%), with an overall CFR of 32.4%. The majority of cases occurred in hospital clinics (92.0%) and 10 cases (8.0%) occurred in laboratories. Most cases occurred among HCWs (86.1%), followed by visitors (12.7%) and hospitalized patients (1.3%). Nursing staff (44.9%) and doctors (32.3%) were the most affected HCWs, followed by laboratory staff (6.3%). The primary transmission route was percutaneous contact (34.3%). Cutaneous contact accounted for 22.2% of cases, followed by exposure to aerosols (proximity) (18.2%), indirect contact (17.2%) and exposure to patient environment (8.1%). CCHFV can cause nosocomial infections with a high CFR. During the care and treatment of patients with CCHF, standard contact precautions, barrier precautions and airborne preventive measures should be applied. In order to improve patient safety and reduce healthcare-associated CCHFV exposure, there is a need for guidelines and education for HCWs to ensure that CCHF is appropriately included in differential diagnoses; this will enable early diagnosis and implementation of infection prevention measures.

Contact Tracing for an Imported Case of Crimean-Congo Hemorrhagic Fever - Experience from a Tertiary Care Center in Kerala, South India

A 30-year-old male working in an abattoir in UAE returned home to Kerala, South India, after getting diagnosed with Crimean-Congo hemorrhagic fever infection. He was admitted to a tertiary care center on the day of arrival and was placed under isolation. Due to the risk of spread of infection among health-care workers, contact-tracing and symptom-monitoring activities were undertaken. As strict standard contact precautions, isolation, contact identification and listing, quarantine, and sensitization of health-care workers were implemented, no secondary cases occurred.

Seroepidemiologic Survey of Crimean-Congo Hemorrhagic Fever Virus in Selected Risk Groups, South Africa

Crimean Congo hemorrhagic fever virus (CCHFV) is endemic in South Africa, but whether mild undiagnosed cases occur is unclear. In a seroepidemiologic survey, only 2 of 387 adults considered at risk because of occupational or recreational activities had evidence of previous infection. Seroprevalence in South Africa remains low within the groups investigated.

Arboviruses in South Africa, known and unknown

The emergence of novel arboviruses of zoonotic potential in South Africa (SA) threatens human health and animal welfare, and affects economic growth and development. These viruses cause severe infections in animals and humans, including neurological diseases, such as encephalitis, resulting in high morbidities, mortalities and economic losses. With increasing reports of Middelburg, Shuni, Sindbis, West Nile and Wesselsbron virus infections in animals and humans in SA, this article reviews and discusses known and currently emerging arboviruses in the country. These reports underscore the need for increased surveillance, vector control management, public health preparedness, focused research, community awareness programs, and the development of rapid and sensitive diagnostic approaches. Furthermore, appropriate medical personnel training and strengthening initiatives for a one-health approach are required to understand and mitigate the emerging arboviral threat to public health.

First serological evidence of Crimean-Congo haemorrhagic fever in febrile patients in Mozambique

OBJECTIVE

Despite its geographical spread, the epidemiology of Crimean-Congo haemorrhagic fever (CCHF) in Sub-Saharan Africa is incompletely understood and its occurrence in Mozambique is unknown. This study was conducted with the aim of investigating the occurrence of CCHF virus (CCHFV) among febrile patients attending an outpatient appointment clinic at three separate primary health care centres in Mozambique.

METHODS

Serum samples were collected from a total of 300 febrile patients aged >5 years who were recruited between March 2015 and March 2016 at three health centres in Mozambique. Each patient was screened for IgG antibodies against CCHFV using an ELISA.

RESULTS

Of the 300 patients enrolled, eight had samples that were positive for anti-CCHFV IgG antibodies, yielding a prevalence rate of 2.7%.

CONCLUSIONS

This study shows for the first time that humans are exposed to CCHFV in Mozambique. It highlights the need for further work to investigate the broader extent of circulating CCHFV in the country and its clinical implications.

Biosafety standards for working with Crimean-Congo hemorrhagic fever virus

In countries from which Crimean-Congo haemorrhagic fever (CCHF) is absent, the causative virus, CCHF virus (CCHFV), is classified as a hazard group 4 agent and handled in containment level (CL)-4. In contrast, most endemic countries out of necessity have had to perform diagnostic tests under biosafety level (BSL)-2 or -3 conditions. In particular, Turkey and several of the Balkan countries have safely processed more than 100 000 samples over many years in BSL-2 laboratories. It is therefore advocated that biosafety requirements for CCHF diagnostic procedures should be revised, to allow the tests required to be performed under enhanced BSL-2 conditions with appropriate biosafety laboratory equipment and personal protective equipment used according to standardized protocols in the countries affected. Downgrading of CCHFV research work from CL-4, BSL-4 to CL-3, BSL-3 should also be considered.

Seroepidemiology of selected arboviruses in febrile patients visiting selected health facilities in the lake/river basin areas of Lake Baringo, Lake Naivasha, and Tana River, Kenya

Introduction: Arboviruses cause emerging and re-emerging infections affecting humans and animals. They are spread primarily by blood-sucking insects such as mosquitoes, ticks, midges, and sandflies. Changes in climate, ecology, demographic, land-use patterns, and increasing global travel have been linked to an upsurge in arboviral disease. Outbreaks occur periodically followed by persistent low-level circulation.

Aim: This study was undertaken to determine the seroepidemiology of selected arboviruses among febrile patients in selected lake/river basins of Kenya.

Methods: Using a hospital-based cross-sectional descriptive survey, febrile patients were recruited and their serum samples tested for exposure to immunoglobulin M (IgM) and IgG antibodies against Crimean–Congo hemorrhagic fever virus (CCHFV), Rift Valley fever virus (RVFV), West Nile virus (WNV), and chikungunya virus (CHIKV). Samples positive for CHIKV and WNV were further confirmed by the plaque reduction neutralization test (PRNT).

Results: Of the 379 samples examined, 176 were IgG positive for at least one of these arboviruses (46.4%, 95% confidence interval [CI] 41.4–51.5%). Virus-specific prevalence for CCHF, RVF, WN, and CHIK was 25.6%, 19.5%, 12.4%, and 2.6%, respectively. These prevalences varied significantly with geographical site (p<0.001), with Tana recording the highest overall arboviral seropositivity. PRNT results for Alphaviruses confirmed that the actual viruses circulating in Baringo were Semliki Forest virus (SFV) and CHIKV, o'nyong nyong virus (ONNV) in Naivasha, and SFV and Sindbis virus (SINDV) in Tana delta. Among the flaviviruses tested, WNV was circulating in all the three sites.

Conclusion: There is a high burden of febrile illness in humans due to CCHFV, RVFV, WNV, and CHIKV infection in the river/lake basin regions of Kenya.

Crimean-Congo hemorrhagic fever among health care workers, Turkey

We investigated 9 cases of Crimean-Congo hemorrhagic fever (1 fatal, 2 asymptomatic) among health care workers in Turkey. Needlestick injuries were reported for 4 workers. Eight received ribavirin. In addition to standard precautions, airborne infection isolation precautions are essential during aerosol-generating procedures. For postexposure prophylaxis and therapy, ribavirin should be given.

Crimean-Congo hemorrhagic fever infections reported by ProMED

OBJECTIVE

There are limited sources describing the global burden of emerging diseases. We reviewed the Crimean-Congo hemorrhagic fever virus (CCHFV) infections reported by ProMED and assessed the reliability of the data retrieved compared to published reports. We evaluated the effectiveness of ProMED as a source of epidemiological data by focusing on CCHFV infections.

METHODS

Using the keywords "Crimean Congo hemorrhagic fever" and "Crimean Congo" in the ProMED search engine, we reviewed all the information about the news and harvested data using a structured form, including year, country, gender, occupation, the number of infected individuals, and the number of fatal cases.

RESULTS

We identified 383 entries reported between January 1998 and October 2013. A total 3426 infected cases were reported, with 451 fatal cases, giving an overall case fatality rate (CFR) of 13%. Out of 144 cases for which the gender was reported, 97 (67%) were male. Most of the cases were reported from Turkey, followed by Russia, Iran, Pakistan, and Afghanistan.

CONCLUSIONS

Case reporting systems such as ProMED are useful to gather information and synthesize knowledge on the emerging infections. Although certain areas need to be improved, ProMED provided good information about Crimean-Congo hemorrhagic fever.

Knowledge levels regarding crimean-congo hemorrhagic Fever among emergency healthcare workers in an endemic region

Background

In this study, we aimed to determine knowledge levels regarding Crimean-Congo hemorrhagic fever (CCHF) among emergency healthcare workers (HCWs) in an endemic region.

Methods

A questionnaire form consisting of questions about CCHF was applied to the participants.

Results

The mean age was 29.6 ± 6.5 years (range 19 - 45). Fifty-four (49.5%) participants were physicians, 39 (35.8%) were nurses and 16 (14.7%) were paramedics. All of the participants were aware of CCHF, and 48 (44%) of them had previously followed CCHF patients. Rates of the use of protective equipment (masks and gloves) during interventions for patients who were admitted to the emergency service with active hemorrhage were 100% among paramedics, 76.9% among nurses and 61.1% among physicians (P = 0.003). Among 86 (78.9%) HCWs who believed that their knowledge regarding CCHF was adequate, 62 (56.9%) declared that they would prefer not to care for patients with CCHF (P = 0.608).

Conclusions

The use of techniques to prevent transmission of this disease, including gloves, face masks, face visors and box coats, should be explained to emergency room HCWs, and encouragement should be provided for using these techniques.

Investigation of Crimean-Congo hemorrhagic fever virus transmission from patients to relatives: a prospective contact tracing study

We investigated the possibility of transmission of Crimean-Congo hemorrhagic fever (CCHF) virus through respiratory and physical contact. In this prospective study, we traced 116 close relatives of confirmed CCHF cases who were in close contact with the patients during the acute phase of the infection and evaluated the type of contact between patients and their relatives. These relatives were followed for clinical signs or symptoms indicative of CCHF disease, blood samples of those with and without clinical signs were analyzed for CCHF virus immunoglobulin M and G (IgM and IgG, respectively) by enzyme-linked immunosorbent assay. No close relatives developed any signs or symptoms of CCHF and were negative for CCHF virus IgM and IgG. The results suggest that CCHF virus is not easily transmitted from person to person through respiratory or physical contact.

Crimean-Congo hemorrhagic fever: history, epidemiology, pathogenesis, clinical syndrome and genetic diversity

Crimean-Congo hemorrhagic fever (CCHF) is the most important tick-borne viral disease of humans, causing sporadic cases or outbreaks of severe illness across a huge geographic area, from western China to the Middle East and southeastern Europe and throughout most of Africa. CCHFV is maintained in vertical and horizontal transmission cycles involving ixodid ticks and a variety of wild and domestic vertebrates, which do not show signs of illness. The virus circulates in a number of tick genera, but Hyalomma ticks are the principal source of human infection, probably because both immature and adult forms actively seek hosts for the blood meals required at each stage of maturation. CCHF occurs most frequently among agricultural workers following the bite of an infected tick, and to a lesser extent among slaughterhouse workers exposed to the blood and tissues of infected livestock and medical personnel through contact with the body fluids of infected patients. CCHFV is the most genetically diverse of the arboviruses, with nucleotide sequence differences among isolates ranging from 20% for the viral S segment to 31% for the M segment. Viruses with diverse sequences can be found within the same geographic area, while closely related viruses have been isolated in far distant regions, suggesting that widespread dispersion of CCHFV has occurred at times in the past, possibly by ticks carried on migratory birds or through the international livestock trade. Reassortment among genome segments during co-infection of ticks or vertebrates appears to have played an important role in generating diversity, and represents a potential future source of novel viruses. In this article, we first review current knowledge of CCHFV, summarizing its molecular biology, maintenance and transmission, epidemiology and geographic range. We also include an extensive discussion of CCHFV genetic diversity, including maps of the range of the virus with superimposed phylogenetic trees. We then review the features of CCHF, including the clinical syndrome, diagnosis, treatment, pathogenesis, vaccine development and laboratory animal models of CCHF. The paper ends with a discussion of the possible future geographic range of the virus. For the benefit of researchers, we include a Supplementary Table listing all published reports of CCHF cases and outbreaks in the English-language literature, plus some principal articles in other languages, with total case numbers, case fatality rates and all CCHFV strains on GenBank.

Seroprevalence of Crimean Congo hemorrhagic fever virus in Ijara District, Kenya

Crimean-Congo hemorrhagic fever (CCHF) is a tick-borne viral disease mainly affecting pastoralists who come in contact with animals infested with Hyalomma ticks, which are the key vectors of CCHF virus (CCHFV). CCHFV has been detected among these ticks in parts of North Eastern Kenya. This study aimed to identify acute cases of CCHF, and to determine the extent of previous exposure to CCHFV in an outpatient population attending Sangailu and Ijara health centers, Ijara District, North Eastern Kenya, presenting with acute febrile illnesses. A total of 517 human serum samples were collected from these patients. The samples were screened for the presence of IgM and IgG antibodies to CCHF using CCCHF-IgG and IgM ELISA test kits. A multivariable logistic regression model was used to investigate the risk factors associated with evidence of exposure to CCHFV. A single patient tested positive for anti-CCHF IgM, while 96 were positive for anti-CCHF IgG. The seroprevalence of CCHFV was 23% in Sangailu and 14% in Ijara. Most exposed persons were aged 40-49 years. The likelihood of exposure was highest among farmers (29%). Age, location, and contact with donkeys were significantly associated with exposure to CCHFV. Acute CCHFV infections could be occurring without being detected in this population. This study confirms human exposure to CCHF virus in Ijara District, Kenya, and identifies several significant risk factors associated with exposure to CCHFV.

Crimean-Congo hemorrhagic fever, Kazakhstan, 2009-2010

We evaluated Crimean-Congo hemorrhagic fever (CCHF) surveillance data from southern Kazakhstan during 2009–2010 and found both spatial and temporal association between reported tick bites and CCHF cases. Public health measures should center on preventing tick bites, increasing awareness of CCHF signs and symptoms, and adopting hospital infection control practices.

The emergence and maintenance of vector-borne diseases in the khyber pakhtunkhwa province, and the federally administered tribal areas of pakistan

Human populations throughout much of the world are experiencing unprecedented changes in their relationship to the environment and their interactions with the animals with which so many humans are intimately dependent upon. These changes result not only from human induced changes in the climate, but also from population demographic changes due to wars, social unrest, behavioral changes resulting from cultural mixing, and large changes in land-use practices. Each of these social shifts can affect the maintenance and emergence of arthropod vectors disease or the pathogenic organisms themselves. A good example is the country of Pakistan, with a large rural population and developing urban economy, it also maintains a wide diversity of entomological disease vectors, including biting flies, mosquitoes, and ticks. Pathogens endemic to the region include the agents of piroplasmosis, rickettsiosis, spirochetosis, and viral hemorrhagic fevers and encephalitis. The northwestern region of the country, including the Khyber Pakhtunkhwa Province (KPK), formerly the North-West Frontier Provence (NWFP), and the Federally Administered Tribal Areas (FATA) are mountainous regions with a high degree of habitat diversity that has recently undergone a massive increase in human population density due to an immigrating refugee population from neighboring war-torn Afghanistan. Vector-borne diseases in people and livestock are common in KPK and FATA regions due to the limited use of vector control measures and access to livestock vaccines. The vast majority of people in this region live in abject poverty with >70% of the population living directly from production gained in animal husbandry. In many instances whole families live directly alongside their animal counterparts. In addition, there is little to no awareness of the threat posed by ticks and transmission of either zoonotic or veterinary pathogens. Recent emergence of Crimean–Congo hemorrhagic fever virus in rural populations, outbreaks of Dengue hemorrhagic fever have been reported in the region, and high prevalence of cattle infected and co-infected with multiple species of hemoparasites (Theileria, Babesia, Anaplasma). The emergence of which has followed the increased density of the rural population due to an influx of refugees from violent conflicts in Afghanistan and is exacerbated by an already impoverished society and wide diversity of potential arthropod vectors. These human outbreaks may be exacerbated by episodes of social upheaval but are also tied to the historically close association of people in the region with their livestock and subsequent zoonosis that result from spillover from co-habitation with infected domestic animals.

Crimean-Congo hemorrhagic fever: a first case from Abbottabad, Pakistan

Crimean-Congo hemorrhagic fever (CCHF) is a deadly viral disease that is endemic in some parts of Pakistan. We report here the first ever case of CCHF from Abbottabad. The patient presented with abdominal pain, hematemesis and low platelets, and died within 24hours of admission. The diagnosis was confirmed by PCR for the CCHF virus. Because of the aggressive infection-control measures adopted, secondary and nosocomial spread was prevented.

Knowledge and attitude toward Crimean-Congo haemorrhagic fever in occupationally at-risk Iranian healthcare workers

We assessed the knowledge and attitude (K&A) toward Crimean-Congo haemorrhagic fever (CCHF) of occupationally at-risk healthcare workers (HCWs). A cross-sectional survey was performed in three referral hospitals in the Systan-Baluchestan and Isfahan provinces of Iran where CCHF is highly endemic. In all, 191/209 eligible HCWs were enrolled (response rate: 93%). All but 11 (5.8%) had heard of CCHF. The mean K&A scores of the respondents were 50.34% and 79.25%, respectively. The correlation between K&A was significant (correlation coefficient: 0.542; P<0.001). Being a physician, working in Isfahan (versus the relatively deprived Systan-Baluchestan) and relying on academic material rather than local media were independent factors significantly associated with more knowledge; higher education and laboratory staff with better attitude were also significant factors. Although HCWs showed the best K&A for preventive measures, only 44% wore gloves and masks for contact with CCHF patients and 22% failed to observe any safety measure. Those with a history of percutaneous contact (6.3%) had significantly lower knowledge scores (P=0.047). There is a need to establish professional education campaigns in highly endemic deprived areas in order to improve physicians' attitudes, encourage nurses' use of academic materials and increase the knowledge of less-educated HCWs.

Crimean-Congo haemorrhagic fever

Crimean-Congo haemorrhagic fever (CCHF) is an often fatal viral infection described in about 30 countries, and it has the most extensive geographic distribution of the medically important tickborne viral diseases, closely approximating the known global distribution of Hyalomma spp ticks. Human beings become infected through tick bites, by crushing infected ticks, after contact with a patient with CCHF during the acute phase of infection, or by contact with blood or tissues from viraemic livestock. Clinical features commonly show a dramatic progression characterised by haemorrhage, myalgia, and fever. The levels of liver enzymes, creatinine phosphokinase, and lactate dehydrogenase are raised, and bleeding markers are prolonged. Infection of the endothelium has a major pathogenic role. Besides direct infection of the endothelium, indirect damage by viral factors or virus-mediated host-derived soluble factors that cause endothelial activations and dysfunction are thought to occur. In diagnosis, enzyme-linked immunoassay and real-time reverse transcriptase PCR are used. Early diagnosis is critical for patient therapy and prevention of potential nosocomial infections. Supportive therapy is the most essential part of case management. Recent studies suggest that ribavirin is effective against CCHF, although definitive studies are not available. Health-care workers have a serious risk of infection, particularly during care of patients with haemorrhages from the nose, mouth, gums, vagina, and injection sites. Simple barrier precautions have been reported to be effective.

Intracellular localization of Crimean-Congo Hemorrhagic Fever (CCHF) virus glycoproteins

Background

Crimean-Congo Hemorrhagic Fever virus (CCHFV), a member of the genus Nairovirus, family Bunyaviridae, is a tick-borne pathogen causing severe disease in humans. To better understand the CCHFV life cycle and explore potential intervention strategies, we studied the biosynthesis and intracellular targeting of the glycoproteins, which are encoded by the M genome segment.

Results

Following determination of the complete genome sequence of the CCHFV reference strain IbAr10200, we generated expression plasmids for the individual expression of the glycoproteins G_N and G_C, using CMV- and chicken β-actin-driven promoters. The cellular localization of recombinantly expressed CCHFV glycoproteins was compared to authentic glycoproteins expressed during virus infection using indirect immunofluorescence assays, subcellular fractionation/western blot assays and confocal microscopy. To further elucidate potential intracellular targeting/retention signals of the two glycoproteins, GFP-fusion proteins containing different parts of the CCHFV glycoprotein were analyzed for their intracellular targeting. The N-terminal glycoprotein G_N localized to the Golgi complex, a process mediated by retention/targeting signal(s) in the cytoplasmic domain and ectodomain of this protein. In contrast, the C-terminal glycoprotein G_C remained in the endoplasmic reticulum but could be rescued into the Golgi complex by co-expression of G_N.

Conclusion

The data are consistent with the intracellular targeting of most bunyavirus glycoproteins and support the general model for assembly and budding of bunyavirus particles in the Golgi compartment.

Bi-annual surge of Crimean-Congo haemorrhagic fever (CCHF): a five-year experience

OBJECTIVE

To determine the peak time of outbreak of Crimean-Congo haemorrhagic fever (CCHF) and to highlight the disease-specific areas in the Balochistan province of Pakistan.

DESIGN

A hospital-based case-series study.

PLACE AND DURATION

A five-year study was conducted by the Department of Pathology in collaboration with the Department of Medicine, Sandeman Provincial Teaching Hospital, Quetta, Balochistan, Pakistan, from 1 March 1997 to 28 February 2002.

PATIENTS AND METHODS

A total of 135 cases were included in the study based on a high index of suspicion of CCHF. The mean age was 33.5+/-18.7 years. Two sets of blood samples were drawn on admission; one set was sent for urgent routine investigations while the other was sent to CDC, Atlanta, USA, for confirmation.

RESULTS

The study showed that CCHF was more common between March and May and again, between August and October, depicting a bi-annual surge. Out of 135 suspected cases, 83 (61.4%) were confirmed to have CCHF and were given platelet concentrate and ribavirin. It ws observed that CCHF was more common in specific areas of the province.

CONCLUSIONS

It is essential to raise the level of knowledge regarding CCHF, especially in disease-specific areas, focussing on the peak outbreak periods.

Recombinant nucleoprotein-based serological diagnosis of Crimean-Congo hemorrhagic fever virus infections

An enzyme-linked immunosorbent assay (ELISA) using recombinant nucleoprotein (rNP) was reported for the detection of immunoglobulin G (IgG) antibodies to Crimean-Congo hemorrhagic fever (CCHF) virus (CCHFV). The immunoglobulin M (IgM)-capture ELISA was developed for the diagnosis of CCHFV infections, using CCHFV rNP as an antigen. These newly developed assays were applied to a study of a CCHF-outbreak and evaluated with sera collected from patients diagnosed as having CCHF by positive reverse transcription-polymerase chain reaction (RT-PCR) and by detection of IgG response. IgM antibodies to CCHFV were detected in 10 of the 13 patients. IgM antibodies to the rNP of CCHFV were detected by the CCHFV rNP-based IgM-capture ELISA in all 6 patients in whom IgG responses were demonstrated, while it was not detected in the 10 patients in whom IgG responses were not demonstrated. Furthermore, the IgM antibodies were detected in 6 of the 61 residents living a CCHF endemic area during the endemic season, while it was not detected in any of the 48 Japanese residents that had never visited the CCHF endemic area. It is concluded that this newly developed CCHFV rNP-based IgM-capture ELISA is a useful method for the diagnosis of CCHFV infections.

Lessons from nosocomial viral haemorrhagic fever outbreaks

The outbreak of Marburg haemorrhagic fever in Angola in 2004-2005 shows once again the devastating and rapid spread of viral haemorrhagic fevers in medical settings where hygiene practices are poorly applied or ignored. The legacy of years of war and poverty in Angola has resulted in very poor medical education and services. The initial high rate of infection among infants in Angola may have been related to poor hospital practices, possibly administration of vaccines. Though the outbreak in Angola was in a part of Africa not previously known to have filovirus infection, prior ecological modelling had predicted this location and many others. Prevention of future outbreaks will not be easy. The urgent need is dissemination of knowledge and the training, discipline and resources for good clinical practice. Educating the public to demand higher standards could be a powerful tool. Good practices are difficult to establish and maintain on the scale needed.

Genetic analysis of Crimean-congo hemorrhagic fever virus in Iran

Crimean-Congo hemorrhagic fever (CCHF) is a potentially fatal disease caused by a tick-borne virus in the family Bunyavridae. The disease occurs in parts of Africa, Asia, Middle East, and Eastern Europe. During recent years, an increasing number of human CCHF cases have been diagnosed in Iran, but very little information is available on the prevalence and genetic diversity of CCHFV in Iran. In the present study, CCHF virus (CCHFV) isolates from nine Iranian patients infected during 2002 were examined genetically. Nucleotide sequencing of the S- and M-segments, encoding the nucleocapsid protein (NP) and the glycoproteins, respectively, revealed that the different isolates were related closely to each other with nucleotide sequence identities exceeding 98% for both S- and M-segments. Phylogenetic analysis of partial S-segment nucleotide sequences showed that the viruses clustered along with strains from Pakistan and Madagascar in one distinct lineage. Phylogenetic analysis also demonstrated that the Iranian isolates examined in this study and the previously published CCHFV strain ArTeh193-3 clustered into different genetic groups, indicating that at least two genetic lineages of CCHFV could be co-circulating in Iran.

Crimean-Congo hemorrhagic fever in Sistan and Baluchestan Province of Iran, a case-control study on epidemiological characteristics

OBJECTIVES

Several cases of Crimean-Congo hemorrhagic fever (CCHF), an arboviral disease, have been reported since summer 1999 in different areas of Iran. The main objectives of this research were to determine the most important means and patterns of transmission and the epidemiologic characteristics of this disease.

DESIGN

In this population-based case-control study, 24 patients from Zabol and Zahedan Districts in the Sistan and Baluchestan province, reported to the Center for Disease Control of Iran, were compared with 300 controls. The controls were sampled through the 'probability proportional to size cluster sampling' method from the general population of the same districts. The following variables were checked: age, sex, living environment (rural versus urban), education years, job, past history of tick bite, contact history with livestock, history of livestock slaughtering, presence of a designated place for animals at home, history of keeping livestock in the house.

RESULTS

Variables which increased the chance of disease include: history of slaughtering (OR = 7.57, CI: 2.21-25.91), high-risk occupations (OR = 4.97, CI: 0.97-25.43), history of tick bite (OR = 105.89, CI: 9.32-1202.44), age above 40 years (OR = 7.32, CI: 1.06-50.26).

CONCLUSION

The results of this study confirm that the scheme of risk factors and risk groups for Crimean-Congo hemorrhagic fever (CCHF) in Iran do not differ substantially from the other parts of the world. Even though tick bite is one of the most important risk factors for CCHF, it cannot explain all cases and there are other important risk factors such as high-risk occupations and having contact with livestock. Even taking care of livestock for a short period at home can increase the chance of contracting CCHF.

Sequence determination of the Crimean-Congo hemorrhagic fever virus L segment

Crimean-Congo hemorrhagic fever (CCHF) virus is highly pathogenic for humans and remains the only Category A virus for which full sequence information is currently unavailable. In this study we completed CCHF genome characterization by determining the L segment sequence using Dugbe and CCHF virus-specific oligonucleotides. Sequence alignments revealed the presence of four previously described conserved regions in all Bunyaviridae polymerases. Interestingly, additional regions containing putative Ovarian Tumor (OTU)-like cysteine protease and helicase domains were identified in the L segments of CCHF and Dugbe viruses, suggesting an autoproteolytic cleavage process for nairovirus L proteins.

Reverse genetics for crimean-congo hemorrhagic fever virus

The widespread geographical distribution of Crimean-Congo hemorrhagic fever (CCHF) virus (more than 30 countries) and its ability to produce severe human disease with high mortality rates (up to 60%) make CCHF a major public health concern worldwide. We describe here the successful establishment of a reverse genetics technology for CCHF virus, a member of the genus Nairovirus, family BUNYAVIRIDAE: The RNA polymerase I (pol I) system was used to generate artificial viral RNA genome segments (minigenomes), which contained different reporter genes in antisense (virus RNA) or sense (virus-complementary RNA) orientation flanked by the noncoding regions of the CCHF virus S segment. Reporter gene expression was observed in different eukaryotic cell lines following transfection and subsequent superinfection with CCHF virus, confirming encapsidation, transcription, and replication of the pol I-derived minigenomes. The successful transfer of reporter gene activity to fresh cells demonstrated the generation of recombinant CCHF viruses, thereby confirming the packaging of the pol I-derived minigenomes into progeny viruses. The system offers a unique opportunity to study the biology of nairoviruses and to develop therapeutic and prophylactic measures against CCHF infections. In addition, we demonstrated for the first time that the human pol I system can be used to develop reverse genetics approaches for viruses in the family BUNYAVIRIDAE: This is important since it might facilitate the manipulation of bunyaviruses with cell and host tropisms restricted to primates.

Crimean-congo haemorrhagic fever: a seroepidemiological and tick survey in the Sultanate of Oman

In 1995 and 1996, 4 persons from the Sultanate of Oman were confirmed with clinical Crimean-Congo haemorrhagic fever (CCHF). To assess the prevalence of CCHF virus infection in Oman, a convenience sample of imported and domestic animals from farms, abattoirs and livestock markets was examined by enzyme-linked immunosorbent assay (ELISA) for immunoglobulin G (IgG) antibodies to CCHF virus. Ticks were collected from selected animals, identified, pooled by species, host and location and tested for evidence of infection with CCHF virus by antigen-capture ELISA. Serum samples from individuals working in animal and nonanimal contact-related jobs were also tested for CCHF antibodies. Serological evidence of infection was noted in 108 (22%) of 489 animals. Most of the ticks collected (618 of 912) from all species of sampled livestock were Hyalomma anatolicum anatolicum, a competent vector and reservoir of CCHF virus. 243 tick pools were tested for CCHF antigen, and 19 pools were positive. Of the individuals working in animal contact-related jobs, 73 (30.3%) of 241 non-Omani citizens and only 1 (2.4%) of 41 Omani citizens were CCHF antibody-positive. Butchers were more likely to have CCHF antibody than persons in other job categories. The presence of clinical disease and the serological results for animals and humans and infected Hyalomma ticks provide ample evidence of the presence of CCHF virus in yet another country in the Arabian Peninsula.

Exotic virus infections of military significance. Hemorrhagic fever viruses and pox virus infections

Military personnel are frequently deployed to distant locations around the world under conditions of great stress, which involve potential exposure to hazardous viruses that are not commonly seen in the developed world. This article will provide an overview of two clinical presentations of viral infections of potential military significance: hemorrhagic fever and poxvirus infections. The three viral hemorrhagic fever viruses described--dengue, hemorrhagic fever with renal syndrome, and Congo-Crimean hemorrhagic fever--represent the diversity of potential hemorrhagic fever viruses that military forces may be exposed. Human poxvirus infections are currently uncommon but knowledge of these agents, will again become important should a terrorist threat of the use of smallpox become real and widespread use of vaccinia be considered to protect the military force.

Outbreak of Crimean-Congo haemorrhagic fever in Quetta, Pakistan: contact tracing and risk assessment

In December 1994 in a private hospital in Quetta, Pakistan, 3 health-workers contracted Crimean-Congo haemorrhagic fever (CCHF) after surgery on a bleeding patient who later died. We conducted a retrospective study to determine transmission risks among contacts. Fifty contacts gave blood for antibody tests and answered questions about exposure. Two of four people exposed percutaneously and one of five with cutaneous exposure contracted CCHE The person with cutaneous exposure was a surgeon who tore his glove during surgery and noted blood on his hand but no cut. There were no anti-CCHF antibodies or CCHF cases among persons whose skin came into contact with body fluids other than blood (0/4), who had skin-to-skin contact (0/16) with patients or were physically close to them (0/21). Three index case relatives reported that although 10 family members had cutaneous exposure, none developed CCHF. The family refused blood tests. CCHF transmission in resource-constrained settings can be limited by focusing on avoiding health worker contact with blood.

Crimean-Congo haemorrhagic fever virus infection in the western province of Saudi Arabia

In 1990, an outbreak of suspected viral haemorrhagic fever involving 7 individuals occurred in Mecca in the Western Province of Saudi Arabia. Congo-Crimean haemorrhagic fever (CCHF), not previously known to be present in Saudi Arabia, was incriminated. A study of the epidemiology of this virus was therefore carried out in Mecca, and in nearby Jeddah and Taif in 1991-1993; 13 species of ixodid ticks (5 Hyalomma spp., 5 Rhipicephalus spp., 2 Amblyomma spp., 1 Boophilus sp.) were collected from livestock (camels, cattle, sheep, goats), and of these 10 were capable of transmitting CCHF. Camels had the highest rate of tick infestation (97%), and H. dromedarii was the commonest tick (70%). Attempts to isolate virus from pools of H. dromedarii and H. anatolicum anatolicum were unsuccessful. The source of infection in 3 confirmed cases of CCHF was contact with fresh mutton and, in a suspected case, slaughtering sheep. An investigation in Mecca, which included a serological survey of abattoir workers, identified 40 human cases of confirmed or suspected CCHF between 1989 and 1990, with 12 fatalities. Significant risk factors included exposure to animal blood or tissue in abattoirs, but not tick bites. It is suspected that the CCHF virus may have been introduced to Saudi Arabia by infected ticks on imported sheep arriving at Jeddah seaport, and that it is now endemic in the Western Province.

Seroprevalence of five arboviruses in Zebu cattle in the Central African Republic

Sequential blood samples taken from 237 adult and 147 young Zebu cattle in the Central African Republic (CAR) were examined by enzyme-linked immunosorbent assay for the presence of antibodies to Rift Valley Fever (RVF), Dugbe (DUG), Crimean-Congo haemorrhagic fever (CCHF), Chikungunya (CHIK) and Wesselsbron (WSL) viruses. Antibodies to DUG and CCHF viruses were detected in 70% and 61% respectively, of the sera from adult cattle, probably due to common antigens. This hypothesis is supported by the fact that CCHF virus was isolated only 3 times from ticks, whereas DUG virus was isolated from almost all ticks. Ticks of the genus Hyalorama, the most important vectors of CCHF, are rare on Zebus in CAR. CCHF virus has a limited role in local human pathology, probably because its distribution is limited by the scarcity of its main vector and the immunological barrier resulting from the presence of antibodies to DUG virus. Antibodies to RVF virus were found in about 8% of adult cattle. Zebus do not play an important role in the spread of CHIK and WSL viruses among humans; these viruses were found in only one and 5, respectively, of the 183 cattle examined.

Crimean Congo-haemorrhagic fever treated with oral ribavirin

Crimean-Congo Haemorrhagic Fever (CCHF) is an often-lethal haemorrhagic fever caused by a tick-borne virus. There are no published data on ribavirin treatment of CCHF-infected patients, despite established in-vitro and in-vivo sensitivity. We report three health workers--two surgeons and a hospital worker--infected with CCHF virus in Pakistan who were treated with oral ribavirin 4 g/day for four days, then 2.4 g/day for six days. Intravenous ribavirin was unavailable. All three patients were severely ill with low platelet and white-cell counts, raised aspartate transaminase and evidence of impaired haemostasis. Based on published reports, all had an estimated probability of death of 90% or more. The patients became afebrile, and their haematological and biochemical abnormalities returned to normal within 48 h of ribavirin treatment; all made a complete recovery, and developed IgG and IgM antibody to CCHF virus. Our experience with ribavirin treatment is encouraging, but does not constitute evidence of efficacy. Given the difficulties in gathering adequate treatment data, we propose a consensus protocol for both intravenous and oral treatment of CCHF. This protocol could be distributed to key medical personnel in areas endemic for CCHF and used to provide a firm basis for effective treatment recommendations.