Evaluation of Serum Level of Interleukin-6 in Patients With Crimean-Congo Hemorrhagic Fever in Zahedan, Iran, From 2012 to 2015

Background: Crimean-Congo hemorrhagic fever (CCHF) is caused by a tick-borne virus in the family of Bunyaviridae. It is asymptomatic in infected animals, but it can cause severe hemorrhagic disease in human with mortality rate of 3% to 50%. Viral load and inflammatory cytokines have an important role in the pathogenesis of the disease. Objectives: The current study aimed to investigate the level of interleukin (IL)-6 in patients with CCHF and the relationship of its level with the severity of infection and clinical outcome of patients with CCHF. Patients and Methods: This cross-sectional and prospective study evaluated all patients with confirmed CCHF admitted to Boo-Ali hospital in Zahedan, Southeast of Iran, from March 2012 to Jan 2015. The disease was confirmed by enzyme-linked immunosorbent assay (ELISA) IgM and IgG and /or real time polymerase chain reaction (RT-PCR). Also, a blood sample was drawnon the day of admission to test the level of IL-6 in the serum of patients. Then, the relationship between serum level of IL-6 with the severity of disease and clinical outcome in patients was evaluated. Data was analyzed by Mann-Whitney test and a P < 0.05 was considered significant. Results: Among 50 patients with CCHF (38% female, 62% male with the age range of 18 - 63 years), the serum level of IL-6 was higher than normal (7 pg/mL) in 60% of the patients. According to the severity index disseminated intravascular coagulation score (DIC score), the mean serum level of cytokine in the mild and severe disease were 50.279.4 and 127.3100.2, respectively. There was a significant difference between serum level of IL-6 and severity of disease (P = 0.003). There was no mortality in patients with low or normal serum levels of IL-6. But, in patients with a high serum level of IL-6, seven patients died. Conclusions: Based on the obtained results, it was concluded that a diminished immune response caused by cytokines in acute phase response, can lead to dissemination of virus, severity of illness and increase of the mortality rate.