Crimean-Congo haemorrhagic fever among healthcare workers in Iran 2000–2023, a report of National Reference Laboratory

Abstract

Background

Crimean-Congo haemorrhagic fever (CCHF) is a lethal acute viral zoonosis with a case fatality rate of 5–50%. Due to the potential of human-to human transmission of the disease, healthcare workers (HCWs) are at risk of occupational exposure to CCHF virus. Little is known about CCHF virus route of transmission and risks in Iranian HCWs. Therefore this study was designed to identify the routes of exposure to the CCHF virus among Iranian HCWs.

Methods

From Oct 2000 to Feb 2023, 96 CCHF suspected healthcare workers referred to national reference laboratory were tested for CCHF virus infection by the use of RT-PCR and IgM Capture Enzyme-Linked Immunosorbent Assay (MAC-ELISA) and exposure history of cases were investigated to determine the CCHF virus routes of transmission in nosocomial settings.

Results

Twelve CCHF confirmed cases were identified including seven nurses and five physicians, with the median age of 32.5 years (range 23–53 years) and the median incubation period of 6.8 days (range from 1 to 22 days). None of the cases reported a history of tick bite or close contact with tissues or animal blood. The cases were from Razavi Khorasan (seven cases), Sistan and Baluchistan (two cases), Isfahan (one case), South Khorasan (one case) and Fars (one case). Percutaneous exposure (needle stick) (three cases), mucosal exposure (blood splash in to face) (three cases) and skin contact with blood (three cases) constituted the most prevalent routes of transmission. Since 2013, no CCHF cases have been identified among Iranian HCWs.

Conclusions

In healthcare settings, physicians and nurses are at risk of nosocomial CCHF virus infection. The routes of transmission mainly include direct exposures via needle-stick, mucosal or direct contact with the skin to infected blood. Continuous education and implementation of infection prevention and control measures are key factors to minimize the incidence of healthcare related CCHF.

Background

Crimean-Congo haemorrhagic fever (CCHF) is an acute, viral, zoonotic disease that is endemic in more than 30 countries in a vast geographical area of Asia, Africa, Eastern Europe, and the Middle East including Iran [1]. CCHF virus, the etiological agent, is a tick-borne RNA virus belonging to the genus Orthonairovirus, family Nairoviridae, in the Bunyavirales order [2]. CCHF is considered as a major public health threat due to its high case fatality rate (5–50%), its propensity for human-to-human transmission, the lack of licensed therapeutics or vaccines, and its zoonotic nature which makes it very difficult to control [3]. Human infection with the CCHF virus most often occurs via the bite of infected ticks, however direct exposure to blood or tissues from viremic animals and infected humans is also a significant route of infection [4, 5]. In nosocomial settings human to human transmission often leads to serious outbreaks with a high mortality rate [6,7,8]. Therefore, healthcare workers (HCWs) have an occupational risk of contracting the disease while they are caring for patients and handling their infectious specimens.

This survey was conducted to study healthcare related CCHF cases referred to the national reference laboratory in Iran, with the aim of better understanding risk factors and routes of nosocomial transmission in the country.

Methods

The objective of this study was to identify the routes of exposure to the CCHF virus among Iranian HCWs by conducting a retrospective analysis of serum samples referred to the Department of Arboviruses and Viral Haemorrhagic Fevers (National Reference Laboratory) from October 2000 to February 2023. The inclusion criteria were: (1) Iranian Nationality, (2) working in a health care setting and (3) being suspected to CCHF according to the CCHF national surveillance system (sudden onset of the clinical symptoms including fever, myalgia with or without hemorrhagic manifestations and direct contact with blood/body fluids/tissues of CCHF cases). According to inclusion criteria, a total of 96 CCHF suspected Iranian healthcare workers were included and demographic, epidemiologic, laboratory, and clinical data from the patient records were collected.

Serum samples form patients were tested for CCHF virus infection by the use of RT-PCR and IgM Capture Enzyme-Linked Immunosorbent Assay (MAC-ELISA) as previously described [9]. MAC-ELISA was carried out using inactivated CCHF virus antigen from suckling mouse brain homogenates. Briefly, the goat IgG to human IgM diluted in 1X phosphate-buffered saline (PBS) was coated and incubated overnight at 4°C. Diluted sera (in PBS with 0.05% Tween (PBST) and 0.3% skimmed milk (PBSTM)) were added and incubated for 1 hour at 37°C. After adding antigen and incubating for an additional hour at 37°C, diluted hyperimmune mouse anti-CCHF virus ascitic fluid in PBSTM was included and incubated for 1 hour at 37°C. Horseradish peroxidase (HRP) conjugated secondary antibody was appended and incubated for another 1 hour at 37°C. Finally, hydrogen peroxide and 3, 3’, 5, 5’ tetra methyl benzidine (TMB) were added and incubated for 15 min at room temperature. By adding 4 N H2SO4 the enzymatic reaction stopped and the optical density (OD) measured at 450 nm. ELISA test for IgG detection was done based on set up protocols.

Viral RNA was extracted from sera using the QIAamp Viral RNA Kit according to the manufacturer’s instructions (Qiagen GmbH, Hilden, Germany). The RT-PCR test was performed using the following specific primers (Iran F2 5′-TGGACACCTTCACAAACTC-3′ and Iran R3 5′-GACAATTCCCTACACC-3′) and One-Step RT-PCR Kit (Qiagen GmbH, Hilden, Germany). The PCR program was: 30 min at 50 °C, 15 min at 95 °C, followed by 40 cycles including 30s at 95 °C, 30s at 50 °C, 45s at 72 °C, before a final extension step at 72 °C for 10 min. A confirmed RT-PCR-positive serum was used as positive control and for negative control, no template control (NTC) was used in the RT-PCR tests [10].

Results

A total of twelve (12.5%) CCHF positive HCWs, including seven (58.3%) nurses, two (16.7%) general practitioners, two (16.7%) gynecologists and one (8.3%) intern were detected. The results of ELISA and RT-PCR showed IgM positivity and viral genome and 3 (25%), and 11 cases (91.7%) respectively. Two cases (16.6%) were positive for both IgM and RT-PCR. Their median age was 32.5 years (range 23–53 years), four (33.3%) were males. The demographic features of the cases are represented in Table 1.

Table 1 Demographic, clinical, laboratory features and routes of exposure of CCHF positive Iranian healthcare workers

The geographical distribution of patients was as follows: seven (58.3%) from Razavi Khorasan, two (16.7%) from Sistan and Baluchistan, one (8.3%) from Isfahan, one (8.3%) from South Khorasan and one (8.3%) from Fars (Fig. 1). The first case was documented in 2001 and the last one was detected in 2012 (Table 1).

Fever (100%), myalgia (75%), nausea/vomiting (58.3%) and headache (58.3%) were the most obvious clinical symptoms. Epistaxis (41.7%) was the most frequent haemorrhagic presentation. Thrombocytopenia (100%), elevated aminotransferases (75%) and leukopenia (66.7%) were the most frequent laboratory findings in the cases. None of the cases reported a history of tick bite or close contact with tissues or blood from animals.

Fig. 1

Space-time map demonstrating the number of Crimean-Congo Hemorrhagic Fever (CCHF) cases in Iran (a) and CCHF cases among healthcare workers (b) from 2000–2023

The most common modes of transmission were percutaneous exposure through needle stick injury in three cases (25%), mucosal exposure via blood splashes in to face, in three cases (25%) and skin contact with blood in three cases (25%).

Eleven out of twelve patients were administered ribavirin therapy according to guidelines of National Committee of Viral Haemorrhagic Fevers [14]. The case who did not receive ribavirin was treated with antibiotics and IVIG, this individual recovered. Two deaths were observed; a nurse form Birjand (2012) who received ribavirin therapy (with unknown date of administration) but died after 5 days post symptom onset. The second case was an intern from Mashhad (2012) who received ribavirin therapy 6 days after onset of symptoms due to his Glucose-6-phosphate dehydrogenase deficiency due to risk of Ribavirin-induced anemia [15].

The incubation period median was 6.8 days with a range from 1 to 22 days.

Discussion

CCHF is a potentially lethal viral disease and human-to-human transmission has been well documented. Healthcare workers living in endemic areas are at risk of CCHF virus infection. Several reports from the UAE, Iran, Pakistan, India, Turkey and South Africa have described nosocomial CCHF among healthcare workers [6, 8, 11, 16, 17].

This retrospective survey of the national reference laboratory records revealed a total of 12 CCHF cases in CCHF suspected Iranian healthcare workers. As shown in Table 1, from 2013 onwards, no healthcare-associated CCHF has been observed in Iran indicating the effectiveness of national surveillance educations with respect to infection prevention control to reduce the risk of CCHF virus transmission in healthcare settings.

CCHF incidence has a seasonal pattern and the majority of the cases are observed in the summer months [1] when Hyalomma tick activity is at maximum. Consistently, nine out of eleven (81.8%) patients in this survey were identified in June and July. However, two cases were observed in September and December corroborating the fact that in endemic areas, CCHF can also occur in colder months. In a study of CCHF among Iranian children, the disease was detected in all months [9]. In addition, the occurrence of CCHF in winter has been reported in Turkey and Russia [18, 19]. The results of the current study showed that nurses and physicians are at the highest risk of infection in nosocomial settings and no secondary cases to family members were observed. Similarly, in a retrospective cross-sectional study from Turkey, 47 out of 51 healthcare-related exposures were recorded among physicians or nurses [20]. Additionally, all nine cases of HCWs with occupational exposure to CCHF virus who were admitted to Ankara Numune Education and Research Hospital, Turkey between 2004 and 2011 were physicians and nurses [21]. Therefore, it can be concluded that healthcare workers who are in direct contact with the patient are at an elevated risk to contract CCHF.

High-risk activities including needle-stick injury, surgery, improper manipulation of infected substances, and interventions which control haemorrhage have been implicated as the especially hazardous practices for CCHF virus transmission to HCWs [20,21,22,23]. Here, percutaneous (needle stick injury), mucosal (blood splash to the face and eyes) and skin exposure with blood were the most prevalent routes of virus transmission. In agreement with these findings, needle stick injury and mucosal exposure have been reported as the main routes of exposure in Turkey [20]. Therefore, healthcare workers providing supportive care for CCHF patients should be well educated about infection prevention and control procedures focusing on the appropriate use of personal protective equipment (PPE) and sharps safety [20]. Additionally, attention should be focused on the use of PPE during low-risk procedures as illustrated in this study where transmission was observed in two cases. Similar observations have been reported in Turkey [22].

Airborne transmission of CCHF virus is a matter of debate. While epidemiological studies demonstrate that airborne transmission of viral haemorrhagic fevers cannot easily happen [22], there is nevertheless some evidence supporting this possibility [12, 21, 24]. Therefore, airborne precautions have been recommended during aerosol-generating medical procedures performance for CCHF patients [24]. Interestingly in this study, one nurse was infected with CCHF virus despite no direct contact with patient or patients’ blood and other body fluids [12]. The nurse was responsible for distributing patients’ drugs including CCHF patients who were hospitalized in the Jahrom city hospital, she was not involved in injection or any other close contact operations with CCHF cases and therefore she most likely entered the patient’s room without wearing a mask. It should be noted that there is no information about the use of N95 masks by the CCHF cases reported here. In conditions that the N95 mask was not applied, the possibility of exposure of infected air/aerosols in the transmission of CCHF virus to the patient should also be considered along with other possible transmission routes.

Opinions differ about the efficacy of ribavirin for prophylaxis and treatment of CCHF. A Cochran review of the use of ribavirin for treating CCHF has recently concluded that there is still insufficient and reliable evidence to show whether ribavirin is effective in treating CCHF [25]. Interestingly, a more recent study which focused on the mutagenic propensity of CCHF virus induced by ribavirin treatment, showed that it was unable to induce error catastrophe and reduce viremia [26]. However, post-exposure prophylaxis with ribavirin has shown promising results in preventing clinical disease or laboratory-confirmed infection among Turkish healthcare workers who had direct exposure to CCHF patients [21, 27]. In the present study, no post-exposure prophylaxis with ribavirin was observed. While if Ribavirin prophylaxis was performed immediately after exposure to the virus, severe symptoms and even death could be prevented [28, 29]. Therefore, it is recommended that considering that there is currently no specific antiviral drug against CCHF virus, the use of ribavirin when there are no contraindications may be beneficial. The incubation period of CCHF generally ranges from 1 to 7 days according to the mode of virus acquisition. In our experience this is usually 1–3 days following the bite of an infected tick, however it can be 5–7 days in relation to direct contact with infected blood or tissues. Our experience also shows that, this period can last up to about 2 weeks [4] and surprisingly in this survey, an unusually long incubation period of 22 days was observed. Long incubation periods (mean 23.6 days, maximum 53 days) have also been indicated among members of the Turkish population [30]. Therefore, in endemic areas, the probability of developing CCHF after incubation periods of more than 2 weeks should be taken into account and It may be crucial to monitor all case of exposure for up to 4 weeks.

Conclusion

This study highlights the considerable risk of nosocomial CCHF virus infection among HCWs, specially, physicians and nurses. The routes of transmission mainly included percutaneous, mucosal, and skin contact with infected blood. Strict infection prevention and control measures, using enhanced protective measures and timely prophylaxis/treatment with ribavirin can be helpful to prevent and manage CCHF in healthcare settings.