Description

• A single stranded RNA virus (genus Alphavirus; family Togaviridae)
• Transmitted by Aedes spp. mosquitoes
• The average incubation period is 2 to 4 days (range 1 to 12 days), followed by the sudden onset of fever, severe arthralgia and myalgia, headaches, photophobia, and a rash (1).
• Clinical signs and symptoms are similar to dengue and Zika virus infection.

Epidemiology

• Originally confined to Africa, Asia, and the Indian subcontinent; has spread to Europe and the Americas
• 2005 to 2014: India, Indonesia, Maldives, Myanmar, and Thailand had >1.9 million cases.
• 2013: Transmission of chikungunya virus in the Americas was first identified in the Caribbean and has spread to 45 countries.
• 2014: Local transmission was identified in Florida, Puerto Rico, and the U.S. Virgin Islands.
• 2015 to 2016: one local transmission reported from United States; ongoing transmission in U.S. territories
• 2017 to July 2018: no transmission reported in United States

Etiology and Pathophysiology

• Bite from Aedes spp. mosquitoes (especially Aedes aegypti and Aedes albopictus)
• A. aegypti also transmits dengue and Zika virus. Coinfection with dengue and/or Zika is possible and increasingly reported.
• Aggressive daytime feeders; bites also occur at night.
• Other modes of transmission: maternal–fetal (2); blood transfusion; corneal grafts (3)
• Pathogenesis is uncertain.

Pregnancy Considerations

• Mother-to-child transmission is seen with intrapartum maternal viremia, often leading to severe neonatal infection, mainly encephalopathy (2).
• Cesarean section with no protective effect on transmission
• Median onset of neonatal disease is 4 days (ranges 3 to 7 days); with fever (100% of cases) and thrombocytopenia (89% of cases)
• There is no evidence for congenital infection in asymptomatic live-born infants exposed during pregnancy (4).

Risk Factors

People living in, or travelling to, an endemic area, not previously infected

General Prevention

• No vaccine or antiviral currently available
• Prevention through use of insect repellants, arthropod control measures, and clothing that minimizes skin exposure, especially during daytime hours