That Which Bends Up
Abstract & Commentary
By Stan Deresinski, MD, FACP, Clinical Professor of Medicine, Stanford; Associate Chief of Infectious Diseases, Santa Clara Valley Medical Center, is Editor for Infectious Disease Alert.
Source: Chikungunya Outbreak in Réunion: Epidemiology and Surveillance, 2005 to Early January 2006 Eurosurveillance Weekly Release—Thursday, February 2, 2006. www.eurosurveillance.org
Synopsis: Chikungunya virus infection is surging in islands of the Indian Ocean, as well in other endemic areas.
More than 5000 people in the Comoros Islands, off the eastern coast of Africa and near Madagascar, became ill with high fever and severe joint paints in the first months of 2005. Their illness, which proved to be due to chikungunya virus infection, then appeared in other Indian Ocean islands, including Mayotte, Mauritius, the Seychelles, and in Reunion, where the outbreak has persisted and expanded, affecting more than 7000 inhabitants through early January, 2006. Since then, disease activity has markedly accelerated on Reunion, with 15,000 new cases occurring in one week alone, and with the total number of cases having exceeded 50,000, representing an attack rate of 9.4 per 1000 residents.
In Reunion, approximately 4% of patients were hospitalized but none were known to have died. A newly identified severe manifestation of infection, meningoencephalitis, was, however, been observed in 12 patients. Six of the 12 were neonates born to mothers with acute infection; all developed symptoms within 5 days of birth.
Commentary
Chikungunya, a positive strand RNA virus of the Alphavirus genus, was first isolated from a human in Tanzania in 1952. It is present in Africa, India, Southeast Asia, Indonesia and the Philippines. Chikungunya has resurged in recent years in a number of locations. As an example, it caused outbreaks in 1999 and 2000 in Kinshasa, DRC, a country in which it had not been identified in almost four decades.1 It has re-emerged in this current decade in Indonesia, where it had previously been quiescent.2 Now it is affecting large numbers of people on islands of the western Indian Ocean near Africa.
In Africa, Chikungunya occurs in predominantly rural tropical areas where it is maintained in a sylvatic cycle and involving a primate-mosquito cycle (with rodents possibly involved), while in Asia, transmission is often urban, with explosive outbreaks, involving a human-mosquito cycle. In each case, the mosquitoes involved are Aedes. Outbreaks in large urban areas of India and Southeast Asia have involved hundreds of thousands of patients. Some of the urban outbreaks have occurred contemporaneously with outbreaks of dengue fever.
Clinical manifestations of chikungunya are similar to those of dengue, with the abrupt onset of fever, chills, headache, photophobia, myalgias, severe arthralgias, and a maculopapular skin eruption. Chikungunya is a Swahili word for "that which bends up", describing the effects of the severe joint pains associated with this disease on the posture of the affected individual. A highly related alphavirus causing similar symptoms seen in Africa, o’nyong-nyong is derived from the Acholi word for joint breaker. Dengue virus, an unrelated flavivirus, which has been known as "break bone fever" for several centuries, causes clinical manifestations which are indistinguishable from those caused by these other 2 viruses. Other viruses that cause severe joint symptoms include Mayaro, Ross River, Sindbis and Barmah Forest, all of which are alphaviruses.
While the infection is usually self-limited, hemorrhagic manifestations have been described. The identification of meningoencephalitis in infants and adults with chikungunya in Reunion appears to be a novel finding.
References
- Pastorino B, et al. Epidemic Resurgence of Chikungunya Virus in Democratic Republic of the Congo: Identification of a New Central African Strain. J Med Virol. 2004;74:277-282.
- Laras K, et al. Tracking the Re-Emergence of Epidemic Chikungunya Virus in Indonesia. Trans R Soc Trop Med Hyg. 2005;99:128-141.
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