During the first six months of 2015, Singapore has seen a relatively mild dengue fever season. According to the National Environmental Agency of Singapore (NEA), there has been 4.292 cases as of July 3, an approximate decrease of 45 percent compared to the same period last year.
In fact, the previous two years, 2014 and 2013, Singapore saw big numbers of the mosquito borne virus. Last year, there were a total of 18,342 reported dengue cases and five deaths. In 2013, the city-state reported record number of cases with more than 22,000, including seven deaths, smashing the previous record of 14,000 cases in 2005.
While the dengue numbers appear relatively mild, at least compared to previous years, health officials worry about at least one factor that could make things change very rapidly–a new predominate dengue strain in circulation.
Officials are saying that an increase in the dengue vector, Aedes mosquito and an increase in transmission of the virus serotype DENV-2. Against a backdrop of a warmer season and low herd immunity, dengue cases may rise in the next few months.
Indeed, certain areas have been reporting a spike in cases in recent weeks. Approximately 100 new cases have been reported in the Bishan North area prompting a “red alert”, according to NEA data published Friday.
Why the concern about DEN-2?
There has been proportionately more dengue cases detected with virus serotype DENV-2 compared to DENV-1, which has been the dominant circulating virus since March 2013. The proportion of DENV-2 cases has risen from 18.3 per cent in 2014 to approximately 44 per cent in mid-May 2015.
Historically, a change in the predominant dengue serotype has been followed by a spike in dengue cases. The last serotype switch, from DENV-2 to DENV-1, took place in March 2013 accompanied by a sharp dengue outbreak that year.
The combination of warmer weather, the DEN-2 serotype, low population immunity and increasing mosquito population has health officials concerned that this could lead to a surge in dengue cases in the coming months.
In order to prevent this from happening, the NEA says the public must first prevent the breeding of its vector, the Aedes mosquito. The Aedes mosquito is easily identifiable by the distinctive black and white stripes on its body. It prefers to breed in clean, stagnant water easily found in our homes. You can get rid of the Aedes mosquito by frequently checking and removing stagnant water in your premises.
They recommend the “10-minute 5-step Mozzie Wipeout”. This includes changing water in vases and bowls on alternate days, removing water from flower pot plates on alternate days, turning over all water storage containers, covering bamboo pole holders when not in use and clearing blockages and put BTI insecticide in roof gutters monthly.
Dengue fever is an infectious disease carried by mosquitoes and caused by any of four related dengue viruses. This disease used to be called “break-bone fever” because it sometimes causes severe joint and muscle pain that feels like bones are breaking.
People get the dengue virus from the bite of an infected Aedes mosquito. It is not contagious from person to person. There are three types of dengue fever in order of less severe to most: the typical uncomplicated dengue fever, dengue hemorrhagic fever (DHS) and dengue shock syndrome (DSS).
The World Health Organization (WHO) estimates there may be 50–100 milliondengue infections worldwide every year. However, new research from the University of Oxford and the Wellcome Trust, using cartographic approaches, estimate there to be 390 million dengue infections per year worldwide.