Wednesday, November 18, 2009

Emerging neuro infections: CHIK, Hendra & Nipah viruses

Ibid (Tyler KT in Arch Neurol 2009)

CHIK virus
infection due to enhanced vector competence. Spread by mosquitoes to humans, togavirus. Abrupt onset fever, joint swelling, myalgia, headache, back pain, and rash. Diagnosis is by CDC IgM and IgG. Rare neurologic cases include encephalitic infections of newborns and elderly.
Other presentations include encephalomyelitis, myeloradiculitis, acute flaccid paralysis (GBS like), encephalopathy and seizures. A mutation in viral envelope dramatically changed infectivity. Endemic travellers to new areas cause infections

Nipah and Hendra viruses.
classification is henipavirus of paramyxovirus. In Australia it first was identified as a highly infectious disease of horses and close human contacts/handlers. Aseptic meningitis and encephalitis occurred in Hendra, a location in Australia.

Nipah virus, closely related, occurred in pig farms in Singapore and Malaysia in 1998. Encephalitis and pneumonitis were common, with a 40 % mortality. The incubation perido was two weeks, with a 3-4 day prodrome. Mortality was 73 %. MRI usually showed multiple small subcortical lesions on T2 and FLAIR images without edema. PEARL- relapsing and delayed onset disease can occur. in 3 % or so average 8 months after first event, with an acute onset the second time. There was an associated systemic vasculitis with thrombosis and parenchymal necrosis in the CNS. Syncytial multinucleated endothelial cells are pathognomomic and occurred in 25 %. A subsequent outbreak in Bangladesh was not associated with pig farms and was shown to be associated with flying foxes and fruit bats with spread through urine of latter. Human to human transmission occurred, including between patients and health care workers.

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