[Viral encephalitis]

Acute viral and other infectious causes of encephalitis usually produce fever, headache, stiff neck and alterations in consciousness, focal neurologic signs and seizures. A large number of viral and nonviral agents can cause encephalitis. Arthropod-borne viruses peak in summer, the tick-borne infections occur in early summer, enterovirus infections in later summer and mumps in the winter and spring.

[Lyme disease]

Lyme disease, which is caused by the tick-borne spirochete Borrelia burgdorferi, usually begins with a characteristic skin lesion erythema chronicum migrans (ECM), that may be followed by neurological or cardiac abnormalities and is accompanied by malaise, fatigue, fever, myalgia, headache, lymphadenopathy and is often followed by arthritis. The disease takes its name from Lyme, Connecticut, where the full spectrum of illness was first described in 1975. It is known to be a multisystemic infectious disease. Because culture and direct visualisation of spirochetes are often negative in Lyme disease, serological testing has been the only practical laboratory aid in diagnosis and primarily clinical findings.