In January 2019, the Caribbean Public Health Agency (CARPHA) warned the Caribbean region of an expected spike in dengue fever and called on communities to exercise caution and support the elimination of mosquito breeding sites to help combat the virus.
A full year later, the number of individuals in the Americas having contracted the mosquito-borne virus is approaching 3 million with at least 1,372 recorded deaths— the highest number of cases on record. The Pan American Health Organisation (PAHO) and other experts have pointed to climate change as one of the leading causes for the surge in numbers, with poor environmental management and increased adaptability of mosquitoes listed as other causes.
Dengue is transmitted by a bite from an infected Aedes aegypti mosquito. This is the same species … [+]
According to Executive Director of CARPHA, Dr Joy St. John, “The Aedes Aegypti mosquito has adapted its life cycle to human habits and habitation. The period between outbreaks has shortened from 5 to 7 years to 2 to 4 years and more than one country is experiencing outbreaks all at once.”
Some countries such as Barbados, the Bahamas, St. Vincent & the Grenadines and Saint Lucia managed to escape outbreak status in 2019, but others such as Guadeloupe, Belize, Saint Martin and Dominica were not so lucky.
The Caribbean country that was most affected by dengue in 2019, in terms of new cases per 100,000 inhabitants, was Antigua & Barbuda. Despite Brazil’s exponential increase in infection between 2018 and 2019 and its shockingly high overall figures (representing 71% of all cases in the Americas), the relative numbers were significantly higher on the twin island state. “At this point we are in an outbreak,” confirmed Chief Medical Officer Dr Rhonda Sealey-Thomas on the Antiguan news talk programme, Observer AM.
On December 15th, a Jamaica Observer article, entitled “Worst Medical Crisis Ever” referred to the dengue outbreak as “the Caribbean’s greatest nightmare” and “the worst catastrophe to have happened around the region in its history.” The Jamaica Observer reported that in early December, 66 deaths from the disease had been confirmed on the Northern Caribbean Island, with many doctors insisting that the actual numbers were in fact much higher than reported. The Minister of Health and Wellness, Dr Christopher Tufton has refuted these claims.
A December 29th article in the New York Times, entitled “Climate change, crime and political chaos: A deadly mix in Honduras dengue epidemic,” reports that there have been 175 dengue-related deaths in Honduras alone, equating to more than 40% of the 400 dengue deaths in Central America. Honduras recorded more than 107,000 cases of the viral disease— more than 13 times the number recorded in the previous year and more than 50 times the recorded deaths.
The increased severity of dengue infection during 2019 has been attributed in part to the fact that the 4 subtypes of the virus (DENV 1, DENV 2, DENV 3, and DENV 4), the latter of which can cause internal haemorrhaging and death, have been circulating simultaneously. Given that an individual develops antibodies upon contracting one subtype, the chances of being infected by a severe strain increases each time the virus is contracted.
A multitude of factors have influenced the exponential surge in dengue, severe dengue and dengue-related deaths, but no trend has been more concerning than climate change, which according to The New York Times, is “threatening to increase the spread of dengue worldwide by expanding the range of the mosquitoes that carry the virus.”
“Climate change has warmed the Caribbean environment and shortened the mosquito breeding cycle. Studies have also demonstrated that the mosquito’s disease transmission capacity is increasing,” says Dr St John.
Dr Joy St John, Executive Director of the Caribbean Public Health Agency (CARPHA)
This has translated into more mosquitoes with greater ability to spread a wider range of diseases, as evidenced by the introduction of Chikungunya and Zika to the Caribbean over the last few years.
“Mosquitoes tend to bite more when it is warmer,” adds Dr James Fletcher, a former St. Lucian minister for sustainable development.
Changes in weather and increased urbanisation have also impacted mosquito-breeding patterns within the region. Climate change precipitates more severe weather events such as hurricanes, floods and droughts. Mosquitoes breed more frequently in the wet season and more frequent severe weather events lead to pooling of water and increased breeding.
The growth of urban areas with increasingly dense populations also provides increased opportunities for infection and a variety of new locations where larvae can grow.
“With the intersection of warmer temperatures, wetter weather events after droughts and mosquito-friendly human habits and habitats, the Caribbean and indeed the world will be experiencing more and more vector borne diseases,” confirms Dr St John.
In December 2019, the European Union provided CARPHA with a grant of $ 4.5 million towards the control of mosquito borne diseases in the region. According to Dr St John, these funds will be used towards laboratory strengthening, training in integrated vector management, insecticide resistance testing and behaviour change interventions.
In the meantime, researchers predict that rising temperatures and unpredictable rainfall patterns will result in dengue migrating to countries outside of the tropics, causing an additional 500 million people around the world to be at risk of contracting similar diseases over the next 30 years.
According to the World Health Organisation, dengue is one of the top 10 threats to global health. The virus has significant implications for tourism and social and economic development. When the Centres for Disease Control issues travel advisories to the region during the tourist season, as it did this year, everyone suffers.
“The need for changes in human habits and mosquito friendly habitats is increasingly evident,” affirms Dr St John. “Integrated Vector Control Management and new technologies to counteract these mosquito friendly conditions are imperative.”