In 2012, the World Health Organization (WHO) estimated that there were approximately 50 million cases of Dengue fever occurring every year worldwide. In 2019 the WHO revised that estimate upwards to 390 million. It’s rarely life threatening, and compared with other mosquito borne viruses it has a very low mortality rate. Nonetheless it’s on the rise, with some local infections reported in Europe for the first time in 2010 and subsequent cases popping up in Spain and France. Symptoms can range from nonexistent to full haemorrhagic fever, but mostly present as severe flu-like symptoms lasting about a week.
Dengue is most prevalent in Asia, Latin America and Africa, but is common elsewhere – including the Western Pacific in countries like Vanuatu which is where yours truly contracted it in the early 90’s. Possibly twice. The first time I was diagnosed by a not-particularly-medical method of a Ni-Vanuatu barman looking at my profusely sweating face and saying “Hem Denggi – siknes blong moskito”. In fact it’s rare to contract Dengue twice so that may well have been some other nameless virus. The second time there was no doubt – I was pretty ill and briefly hospitalized in Port Vila where they diagnosed Dengue and popped me on a drip for couple of days.
Dengue is spread by the aggressive Aedes aegypti (and Aedes albopictus) mosquito which, unlike the malarial Anopheles genus, enjoys a blood meal at any time of day so bite avoidance can be harder. Covering up is difficult during the hot daytime, so you need to use a good repellent, and keep it applied. Obviously we recommend No Mozzie because it is very effective, but use DEET if you prefer.
The above chart shows WHO statistics for 1990 to 2017 of reported Dengue Fever cases – an upward trend and a small fraction of actual Dengue incidence. So why is it on the increase? Doubtless climate change and increased temperatures are having an effect in allowing the mosquito to spread further afield, but a much bigger factor is simply population growth and the movement of people.