Dengue: a record breaking 2013?

And with cause: figures recorded since January indicate that this year’s outbreak may soon become a record breaker in most of Southeast Asia. 

Endemic in most of the world’s tropical areas, dengue is caused by 4 strains of the dengue virus, all of them transmitted by the Aedes mosquito, a species that is well accustomed to breeding in urban areas. They bite during the daytime and at dawn and multiply alarmingly during the rainy season leading to outbreaks affecting, in half the cases, children below the age of 15. The disease is often benign but in about 10 per cent of infections can lead to haemorrhagic complications, which might require hospitalisation in an intensive care unit due to the risk of potentially fatal acute shock. When present, clinical manifestations mimic the symptoms of flu with high fever, headache, rash and, more specifically, severe joint and back pain. There is no medication against the virus and the treatment thus aims to improve the symptoms and prevent complications. Dengue confers a lifelong immunity though this is limited to the single viral strain involved. 

The marked increase in the number of cases and fatalities this year is now becoming alarming. In Thailand, as early as mid June, more than 45,000 cases had been reported with 50 deaths, marking a three-fold increase over the same period last year. The north, northeast, south and eastern regions are the most affected. 

The major recrudescence in the disease right at the beginning of the rainy season is obviously a source of concern for the health authorities, especially as significant rainfall is expected during the next few months. In Laos, a country with 6 millions inhabitants, dengue has already lead to 30 deaths, six times higher than in 2012. In Singapore, where the government imposes serious fines for the non-respect of sanitary measures, the incidence of the disease is also much higher than in previous years with more than 9,500 cases and 2 deaths already reported. The Prime Minister has called on 30,000 volunteers to help eliminate the mosquitoes’ breeding sites.

There are several reasons behind the rise of dengue this year, all of them to do with climatic conditions, which have brought warmer temperatures, as well as intense and prolonged rainfall and high humidity levels favourable to the proliferation of the mosquitoes. In addition, the four strains of virus have been found in most outbreaks, unlike in previous years where the presence of one or two strains was identified.

Despite the immunity brought about by past infection, some patients may have contracted another viral type. 

The only preventive measure is to limit, as effectively as possible, the number of mosquito bites, especially in children under 10 years of age who are more susceptible to haemorrhagic complications. For the younger ones, the leisure grounds infested by insects should simply be avoided. Long sleeved clothing should be worn. The use of repellent, preferably one containing DEET (N.N-diethyl-3-methylbenzamide), in regular applications every two to four hours, is recommended as well as the use of mosquito nets.

The elimination of breeding sites is everyone’s duty and requires an unwavering commitment from the concerned health authorities. A piece of good news is the forthcoming vaccine against dengue, effective on 3 viral strains, which could become available in 2015 or 2016. 

 

Dr Gerard Lalande is managing director of CEO-Health, which provides medical referrals for expatriates and customised executive medical check-ups in Thailand. He can be contacted at [email protected].