Friday, January 22, 2016

MMWR: Dengue Outbreak In Hawaii


Although Florida and Texas have both seen minor outbreaks of dengue fever over the past few years, Hawaii is presently seeing the largest outbreak to date, with 230 cases reported on the Big Island over the past few months.

The following is the latest update from the Hawaiian State Department of Health.

Dengue Fever – Hawaii Island Outbreak

The Hawaii Department of Health (HDOH) is investigating a cluster of locally-acquired cases of dengue fever on Hawaii Island (the Big Island). Dengue is not endemic to Hawaii. However, it is intermittently imported from endemic areas by infected travelers. This is the first cluster of locally-acquired dengue fever since the 2011 outbreak on Oahu.  The Big Island and the rest of Hawaii remain safe destinations for visitors and residents.
As of January 21, 2016*:

Since the last update, HDOH has identified 6 new cases of dengue fever.  Currently, as many as 3 of the confirmed cases to date are potentially infectious to mosquitoes. All others are no longer infectious.
Of the confirmed cases, 208 are Hawaii Island residents and 22 are visitors.

188 cases have been adults; 42 have been children. Onset of illness has ranged between 9/11/15 – 1/16/16.

As of today, a total of 962 reported potential cases have been excluded based on test results and/or not meeting case criteria.

Yesterday the CDC's MMWR published a Notes From The Field report on this outbreak, which covers the opening six weeks of this outbreak.  At that time 117 Dengue infections had been identified.

Notes from the Field: Outbreak of Locally Acquired Cases of Dengue Fever — Hawaii, 2015

David Johnston, MPH1; Melissa Viray, MD1; Jenny Ushiroda1; A. Christian Whelen, PhD1; Rebecca Sciulli1; Remedios Gose1; Roland Lee1; Eric Honda1; Sarah Y. Park, MD1 (View author affiliations)

On October 21, 2015, the Hawaii Department of Health (HDOH) was notified of a positive dengue immunoglobulin M (IgM) antibody result in a woman residing on Hawaii Island (also known as the Big Island). The patient had no history of travel off the island, and other family members reported having similar signs and symptoms, which consisted of fever, headache, myalgias and arthralgias, and a generalized erythematous rash. HDOH initiated an investigation to identify any additional cases and potential exposure sources. On October 24, HDOH received report of a group of mainland U.S. visitors who had traveled together on Hawaii Island, including several who had developed a febrile illness. Additionally, on October 27, HDOH was notified of an unrelated person, also on Hawaii Island, with a positive dengue IgM result. As of November 26, 2015, HDOH had identified 107 laboratory-confirmed cases of dengue fever (1), with dates of onset ranging from September 11 to November 18, 2015 (Figure).


All travelers, whether visitors to the state of Hawaii or returning residents, should consult with and advise their health care providers regarding their recent travel if they develop illness within 2 weeks of their return home. All health care providers, especially those in Hawaii, should be familiar with and alert for signs and symptoms of dengue fever, as well as for other more common infections such as leptospirosis, which sometimes mimics dengue infection. 

Additionally, health care providers should know the warning signs and management of potential severe dengue (i.e., dengue hemorrhagic fever) (1). It is important for all persons, and especially for state of Hawaii residents and those on Hawaii Island, to avoid exposure to mosquitoes, eliminate potential mosquito breeding locations from their property, and protect themselves from mosquito bites.

The arrival of Dengue to Hawaii undoubtedly occurred in much the same way that Zika arrived in Brazil, Chikungunya arrived in the Caribbean, and Dengue turned up in South Florida. 

Carried in (unknowingly) by an infected traveler - one who may very well have been asymptomatic or only mildly ill.

Although humans are usually only viremic for a week or 10 days - during this window they are capable of infecting local mosquitoes who partake in a blood meal, even if they aren't symptomatic (see PNAS: Asymptomatic Humans Transmit Dengue Virus To Mosquitoes).

It takes the confluence of a several conditions - a viremic visitor, a competent vector like the Aedes mosquito, the right weather/climatic conditions, and usually a dense population - but when the conditions are right, sustained local transmission (albeit sometimes only temporarily) can occur.

With Zika, Chikungunya, and Dengue making substantial inroads into the Americas, Southeast Asia, and the Pacific - all areas with a substantial tourist trade - the ability for these viruses to hop a plane and turn up in Europe, North America, and other regions where they are not currently active continues to grow.

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