Dengue Fever in Paradise – Hawaii’s Big Island

Dengue fever (also known as “breakbone fever”!) is a mosquito-caused illness.  Those with dengue exhibit disease symptoms which include a sudden onset of fever, severe headaches, eye, joint, and muscle pain, and a rash. The rash typically appears on the hands, arms, legs and feet within 3-4 days after fever begins. Minor bleeding problems can also occur. The symptoms most often cease within 1-2 weeks.

Occasionally, severe illness with dengue (abnormal bleeding and dangerously low blood pressure) can lead to death (dengue hemorrhagic fever).  Subsequent infections with dengue can increase the risk of developing severe illness. There are 4 different types of the virus that causes dengue fever, and having recovered from one type does not confer permanent immunity from the other 3 types.

In November 2015, about a dozen or so people on Hawaii’s Big Island were known to have contracted dengue fever from the bites of local mosquitoes. By mid-November ago, the Hawaii Department of Health reported about 3 dozen cases of dengue fever.  In December, over 140 cases were reported. As of January 8, 2016, 210 cases have occurred, 190 of which are Hawaii Island residents, and 20 are visitors to that island.

A decision was made in November to hire a public relations firm to help with control of the dengue outbreak with a “Fight the Bite” publicity campaign.  Since December, the Centers for Disease Control and Prevention (CDC) became involved.  This is by the largest outbreak of dengue fever in the state of Hawaii since the 9-month-long outbreak on Maui 15 years ago, which lasted from May 2001 until February 2002, with 122 cases having occurred.  There was also a smaller cluster of 5 dengue cases reported on Oahu in 2011.

Hawaii has been also recently been spraying a permethrin-based mosquito insecticide (Aqua-Reslin) to kill adult mosquitoes (an “adulticide”).  A comprehensive mosquito control program should also have a “larvicide” to kill the mosquito larvae before they grow into biting adults, thereby reducing the overall numbers of mosquito.  There’s no word on whether Hawaii has yet initiated this additional control measure.

According to the CDC, The Hawaii Department of Health lacks extensive expertise in insect (i.e., mosquito) control.  This is the rainy season, particularly on much of the Big Island, where November and December are typically the rainiest months of the year in the city of Hilo, located in the northeast of the island.  Hilo in 2015 recorded its warmest year on record, with an average temperature of about 76 degrees.  2015 also turned out to be one of the wettest on record for the island.  These conditions, along with heavy growth containing plants (bromeliads) which store reservoirs of stagnant water where mosquitoes can breed, certainly have promoted the growth of the island’s mosquito population.

Among the “day biting mosquitoes” in Hawaii which can transmit dengue fever are Aedes aegypti and Aedes albopictus (the Asian tiger mosquito).  Aedes aegypti is most active during daylight, and ~2 hours after sunrise and several hours before sunset.  Aedes albopictus also feeds in the daytime, in addition to during dusk and dawn.

Given that this dengue outbreak has mostly been spread among the locals of Hawaii (90% of the cases), the average visitor to this island perhaps has a lesser risk of infection.  But that may also have something to do with the fact the “average tourist” visiting Hawaii spends most of their time in their resort hotel.

Scuba divers and especially more active tourists wishing to take nature hikes while on this island may face a greater risk of contracting dengue from a mosquito bite. An interactive map available through the Hawaii Department of Health shows that the largest number of cases have occurred near Kona and Captain Cook – both popular areas for scuba divers and their families.[i]

Anyone headed to Hawaii’s Big Island at present would be best advised to bring along a sunscreen containing an insect repellent – don’t expect to be able to find any left on the store shelves when you arrive in Hawaii.  The CDC recommends that those applying sunscreen and insect repellent (i.e., DEET) on separately, place the sunscreen on first, followed by the insect repellent.  Finally, if you’re absolutely committed to doing some back-country hiking and camping in the near future on Hawaii’s Big Island, you should likely consider bringing some permethrin-treated clothing with long shirts and long pants.  This outbreak will eventually end, but just perhaps it’s a warning sign of diseases such as dengue will become more permanent in paradise.