Dengue is a serious vector borne virus

by Dr Jerrol Thompson

WHO reports 100 – 400 Million Dengue cases and 22,000 deaths annually. Cummings’ question, “where in the world, you ever hear people dying of dengue” tries to suggest that Dengue is just a mild illness of little concern, rather than the serious vector borne virus, prone to fatal outbreaks.

Before 1970, only nine countries globally had experienced severe dengue epidemics and 18 countries in Latin America and Caribbean had declared mosquito eradication mainly due to the extensive use of DDT. However, in the 80’s DDT’s links to environmental damage, testicular & blood cancers led to it being banned. Severe Dengue now affects most Asian and Latin American countries and the leading cause of hospitalization and death among children and adults in these regions. The largest number of dengue cases ever reported globally was in 2019, where Jamaica had 6,000 cases and 9 deaths. This year 2020, Martinique has 20,000 cases with 10 deaths (7,000 cases in September alone), Guadeloupe 11,200, St. Maarten 2,100, St, Barts 990, St Lucia 500, Brazil, 1.3 Million, etc., all with several deaths. The recent surge in severity is attributed to human habitats harboring Aedes Aegypti and new discoveries about the dengue virus.

The growth of informal squatter settlements in 80’s and 90’s, imported tires and massive quantities of garbage dumped in rivers and ravines provided the perfect breeding habitats. Today thousands of tons of plastics once indiscriminately dumped, go into two sanitary landfills. Most small garbage sites were cleaned-up and policies promoting plastic bottle recycling, Styrofoam banned, reduced plastic bags, Kingstown garbage bins and road cleaning programs, have all helped.

There are dozens of different Mosquitoes in SVG but the dreaded Aedes Aegypti, well adapted to human dwellings and now septic tanks and streams have other unique features. It lays eggs at multiple sites. Eggs can survive for one year. It prefers persons with O-blood, obesity and who are sweaty. Unfortunately fogging only kills the adult mosquito, not the eggs or larva. In some countries Covid-19 lockdowns reduced controls. Climate change, higher temperatures and rain pattens in 2020 have caused massive breeding regionally.

The Hallmarks of Dengue are: Fever, the Most common symptom (82.8%); Headache (82.7%); Myalgia/Joint (78.6%); and Retro-ocular Eye pain (73.4%). Most cases are mild but recent studies explains why some Dengue outbreaks have progressed to bleeding and severe shock.

Dengue belongs to a family of Flaviviridae Viruses. Cousins are Yellow Fever, ZICA, West Nile. These show a strange phenomenon called Antibody Dependent Enhancement (ADE).

Whereas, most viruses cause humans to produce antibodies that neutralize and kill that virus, these viruses may also induce a second type of antibody that do not neutralize. Dengue unfortunately has four distinct strains. When DENV-2 viruses was introduced into the Pacific in the 1970s after absence of 25 years, some islands experienced explosive epidemics. Patients had high virus levels, fatal hemorrhagic shock disease, whereas other neighboring islands only experienced sporadic and mild illnesses.

In The Scientist: August 2020: Prior or pre-existing Zika virus infection can predispose to more severe dengue infection. Children who had had a prior Zika infection had a roughly 12 per cent chance of developing symptomatic dengue, compared with 3.5 per cent chance if child had no prior flavivirus exposure. Prior Dengue or Zika increases risk that a child experiences the most severe dengue symptoms of hemorrhagic fever and shock.

St Vincent experienced Dengue Type 2 outbreak in 2010 and Zika in 2016. In 2020 we have Dengue type 3, with increased severity.

Normally, recovery from Dengue provides lifelong immunity against that particular strain but this cross-immunity-ADE to other strains are only partial and temporary. Subsequent infection with a different strain is more likely to cause severe Dengue due to antibody-dependent enhancement (ADE). Individuals admitted to hospital after an average five days of symptoms compared with three days is linked to severity. Warning signs of severity include bleeding, persistent vomiting or abdominal pain (present in 63 per cent of severe cases).

EARLY TREATMENT. In an historic policy, the Ministry of Health is promoting the use of CARICA PAPAYA LEAF JUICE (CPLJ) which contains Carpaine, flavonoids, etc., which stabilizes platelets. This easy to make juice should be taken on the first or second day of fever and continued twice a day for 3 days. If fever or warning symptoms persists, YOU MUST GO TO THE CLINIC, to avoid dreaded Dengue Shock.