Table. Clinical phases of Crimean-Congo hemorrhagic fever*.

Clinical phase	Duration	Clinical features	Laboratory features
Incubation	3–7 d (3–5 d after tick bite, 5–7 d after exposure to blood or tissue)	Not applicable	Normal-mildly decreased PLT
Prehemorrhagic	1–7 d	Fever, headache, myalgia, dizziness, nausea, vomiting, diarrhea, hyperemia of upper body, conjunctivitis	Viremia (positive PCR), mild leukopenia, mild thrombocytopenia, elevated CK, mild elevation of AST, ALT, and LDH
Hemorrhagic	Begins at day 3–5 of illness	Petechial rash (skin, conjunctiva, mucosa), large cutaneous ecchymoses, gastrointestinal and genitourinary bleeding, hepatosplenomegaly, if fatal (days 5–14 of illness) secondary to MOF, bleeding, shock DIC	Decreasing viremia, in most cases resolved by day 9 of illness, positive serum IgM against CCHFV, leukopenia, anemia, profound thrombocytopenia, marked elevation of AST, elevation of ALT, elevated PT, aPTT, D-dimer and FDP, schistocytes
Convalescence	Up to 1 y	Weakness, malaise, hair loss, anorexia, polyneuritis, impaired memory, vision impairment, hepatic and renal insufficiency	Thrombocytosis, slow decrease in AST and ALT, slow resolution of renal and liver function, positive serum IgG against CCHFV

*ALT, alanine aminotransferase; aPTT, activated partial thromboplastin time; AST, aspartate aminotransferase; CCHFV, Crimean-Congo hemorrhagic fever virus; CK, creatine phosphokinase; DIC, disseminated intravascular coagulation; FDP, fibrinogen degradation products; LDH, lactate dehydrogenase; MOF, multiorgan failure; PT, prothrombin time.