Chikungunya virus (CHIKV) is a re-emerging alphavirus with the most common symptoms of the infection are fever and joint pain and most people recover within a week, though for some people the joint pain can continue for months and even years.

Recently, Asian lineage CHIKV emerged in the Caribbean and expanded to the Americas, and recent clinical and experimental data indicate differences in the pathogenicity between Asian and American lineages. The major outbreaks that have occurred since 2005 in the Indian Ocean islands were attributable to a new Indian Ocean lineage that evolved from the East Central South African (ECSA) lineage.

Scientists at the Central University Hospital in Saint Pierre (Reunion Island) and their colleagues carried out an ambispective cohort study aimed at characterizing clinical and biological features of CHIKV-associated central nervous system (CNS) disease, disease burden, and 3-year neurologic outcome of patients with this condition. All patients hospitalized between September 1, 2005, and June 30, 2006, with CHIKV infection and neurologic symptoms that led to lumbar puncture (LP) eligible for the study.

Patients with positive cerebral spinal fluid (CSF) for CHIKV ribonucleic acid (RNA) or anti-CHIKV immunoglobulin M (IgM) were studied further. Anti-CHIKV IgM assay in the CSF was performed by enzyme-linked immunosorbent assay (ELISA) using the ETIMAX 3000 (DiaSorin; Saluggia, Italy). A one-step TaqMan real-time quantitative polymerase chain reaction (PCR) was performed from CSF samples using the Light LightCycler 2.0 system (Roche Diagnostics; Basel, Switzerland).

Among the 129 CHIKV-infected patients with CNS disease, biological analysis of the CSF was positive for 55 CHIKV RNA or 30 anti-CHIKV IgM in 78 patients and negative in 51 patients. A total of 24 people had encephalitis that was associated with chikungunya virus, for a cumulative incidence rate of 8.6/100,000 people. Encephalitis was more likely to occur in infants and people aged older than 65 years. The incidence rate in infants was 187/100,000 people and it was 37/100,000 people in those aged older than 65. The death rate for those with chikungunya virus-associated encephalitis was 17%. An estimated 30% to 45% of the infected persons with encephalitis had persisting disabilities. The disabilities included behavioral changes and problems with thinking and memory skills in infants, and post-infectious dementia in previously healthy adults.

Patrick Gérardin, MD, the lead author of the study said, “Since there is no vaccine to prevent chikungunya and no medicine to treat it, people who are traveling to these areas should be aware of this infection and take steps to avoid mosquito bites, such as wearing repellent and long-sleeves and pants if possible. These numbers are both much higher than the rates of encephalitis in the USA in these age categories, even when you add together all the causes of encephalitis. The consequences of this encephalitis seem to be particularly harmful in newborns.” The study was published on November 25, 2015, in the journal Neurology.

Related Links:
Central University Hospital in Saint Pierre 
DiaSorin 
Roche Diagnostics