Flu-like illness with fever, headache, nausea/vomiting, and myalgias;
The Far Eastern variety (FEE) causes the most severe disease. All types may cause flaccid paralysis. CEE and Louping ill have a diphasic fever pattern--4-10 days after apparently recovering from the initial febrile illness, the patient develops fever again, this time with symptoms of meningoencephalitis. CEE and Looping ill usually cause a mild illness. [CCDM, 19th Ed., p. 47-9] About one in three people infected with tick-borne encephalitis (TBE) develop symptoms. Initial symptoms include fever, headache, nausea/vomiting, myalgias, and sometimes fasciculations. After a remission of 2-8 days, a minority of patients have the secondary phase of TBE with resumption of high fever, headache, and vomiting. The course for children is usually benign aseptic meningitis. Adults, and especially the elderly, are more likely to suffer complications of meningoencephalitis or meningoencephalomyelitis. Weakness may be temporary or permanent. Of hospitalized patients with Far Eastern encephalitis, up to 20% die, and up to 60% have residual neurological impairment. Hemorrhages have been reported in some cases of TBE. Other findings include tremor, paresthesias, incoordination, dysphagia, dysphasia, leukocytosis (second phase), leukopenia (initial and late phases), thrombocytopenia (initial phase) and elevated transaminases. Patients with TBE (tick-borne encephalitis) and Powassan encephalitis may have weakness and paralysis secondary to myelitis. Tick-borne hemorrhagic fevers (CEE, Powassan, Louping Ill, Russian, FEE, Crimean-Congo, Kyasanur Forest, and Omsk) are typically biphasic illnesses that begin with a flu-like illness and end with hepatomegaly and bleeding diathesis (petechiae, thrombocytopenia, and DIC). [PPID, p. 1883, 1896-7, 3276-7]
There is a 10% case fatality rate for Powassan encephalitis, and 50% of patients have neurological sequelae. Ticks and mammals are the main reservoirs. Effective vaccines have been used in Europe and the former USSR. [CCDM, 19th Ed., p. 47-9] TBEV is maintained in deciduous forest areas in Europe and Asia by ticks (vector and reservoir) and small rodents (amplifying hosts). Transmission can occur after ingestion of unpasteurized milk or cheese from infected goats, sheep, or cows, infrequently through laboratory exposure and slaughtering infected animals, and rarely through blood transfusion or breastfeeding. Seven cases of TBE in travelers to Europe and China were reported between 2000 and 2015. [CDC Travel, p. 326-9]
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