Infectious Diseases

Arboviruses and Pacific Islands

Zika in Polynesia, Chikungunya in Micronesia, Dengue in Melanesia

June 20, 2016
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SYNOPSIS: Presently, arboviruses like Zika and Dengue are a significant contributor to the rise in febrile illness in the Pacific islands.

In 1947, the Zika virus got its name from the Zika forest near Entebbe, Uganda, where it was discovered first in a sentinel rhesus monkey. A flavivirus that can cause fever, rash, joint pain and conjunctivitis, Zika was extracted from a pool of Aedes africanus mosquitos the year after its discovery, and a subsequent study determined that over 6% of residents in the region had developed antibodies specific to the virus.

Late in 2013, outbreaks of Zika fever were confirmed on 15 French Polynesian islands by the French Polynesia Department of Health. Though there were no known deaths or hospitalizations, nearly 100 laboratory confirmed cases and potentially 35,000 suspected cases were reported by Dec. 3. Estimations point to almost 7.6% of the total population having symptomatic infections that lasted an average of 3-6 days. Rash was the most commonly displayed symptom, followed by fever, arthralgia and conjunctivitis. Concurrently there has been an abnormal jump in the cases report of Guillain-Barre syndrome, with each case reported also linked to a viral infection of Zika’s profile. No tests were undertaken, however, so the link was not confirmed.

The only prior substantial Zika outbreak occurred in 2007, where 108 residents of Yap, a Carolina island of the Federated States of Micronesia, reported mild fevers, rashes, arthralgia and conjunctivitis, the hallmark symptoms of Zika infection. Before this outbreak, Zika had only been confirmed in 14 individual patients. Again in this case, there were no hospitalizations or deaths reported.

Similarly in Yap now is the Chikungunya virus, which since late November 2013 has been suspected in over 1,000 cases. No deaths have been reported from this alphavirus. Likewise, Dengue fever has continued to be transmitted around the Pacific, including in Micronesia. Unlike Zika and Chikungunya, Dengue has been active in tropical and subtropical regions for many years now and has already spread into southern France and Florida. Chikungunya is most concentrated around the Indian Ocean and southeast Asia, but has recently reached places as far as Italy and select Pacific islands. Though Dengue is well known and has a high profile, the outbreak of Zika in French Polynesia has subsequently raised awareness about Chikungunya, which is a much more obscure virus.