Dengue on the rise | Sunday Observer

Dengue on the rise

“During the past few months, an increasing trend in the number of dengue cases have been reported in Sri Lanka”, the WHO announced in July this year after it observed a disturbing tendency and a possibility of a sudden spike in dengue.

Although the country did record a moderate number of cases in January this year, by May it started to rise and indicated a disturbing trend until early September. The country has recorded more than 75 dengue deaths so far, already exceeding the annual figure of 52 cases last year.

The unusually high rainfall within the second half of the year would have aggravated the issue, experts pointed out. In 2018, the highest number of dengue cases of 7,278 was reported in January but this year the highest number of 9,459 patients were reported in the month of August.

In 2017, during the worst outbreak of dengue in Sri Lanka’s history, the highest number reported was in June with over 25,000 and August coming second with over 22,000 cases.

Even though there was an increase in dengue patients in August this year, by September there has been a drop.

“The confirmed cases are declining but reporting is not declining,” Dengue Unit Director, Dr.Anura Jayasekera told the Sunday Observer. When asked if this decline of cases in September was a good sign he said that they fear a rise in cases with the persistent high rainfall.

From January to September 2019, the Epidemiology Unit of the Ministry of Health, Nutrition and Indigenous Medicine reported an official number of 51,243 dengue patients. This is a significant increase considering that there were only 51,659 cases in the whole of last year. The Epidemiology Unit data showed a high number of cases of dengue in Colombo, Gampaha, Kalutara and Ratnapura Districts. The least number of cases were reported from Mannar, Mulaitivu and Kilinochchi.

But it is feared that the actual figure, which include the unreported cases is always higher than the official numbers.

The last major outbreak of dengue that gripped the country was recorded in 2017, with a massive 186,100 people contracting the disease in that particular year. Even though there are no signs of such a huge outbreak this year, the Epidemiology Unit of the Health Ministry is keeping its eyes peeled to take action in case of an unfortunate eventuality.

The Health Ministry has been conducting cleaning campaigns in high risk areas. Dr. Jayasekera said they conducted a similar campaign this week from Thursday to Saturday to destroy breeding grounds of the dengue mosquito. The Unit is also using fumigation as a selective method in very high risk areas.” We cannot use it liberally due to adverse environmental issues,” the Director said, explaining that the chemicals used can destroy other insects in the environment. Therefore, source reduction to remove breeding sites is the popular method used by the Unit.

Travel advisory

IAMAT, an international body advising globe-trotters on health matters issued a dengue warning dated September 20 for Sri Lanka on its website. “ OUTBREAK - Recent cases of Dengue have been reported from Sri Lanka. The most affected areas include Colombo, Galle, Kalutara, Ratnapura, and Gampaha,” it read.

The IAMAT said the risk of dengue exists throughout the country and transmission occurs year-round. There are two peak seasons for dengue transmission in Sri Lanka: from October to December and from May to July.

WHO says dengue which is a mosquito-borne viral disease,’ has rapidly spread in all regions of WHO in recent years. Dengue is widespread throughout the tropics, with local variations in risk influenced by rainfall, temperature and unplanned rapid urbanisation.’

Dengue transmission

The dengue virus is transmitted by female mosquitoes mainly of the species Aedes aegypti and, to a lesser extent, Ae. albopictus. The same mosquito transmits chikungunya, yellow fever and zika infection. According to the WHO, severe dengue was first recognised in the 1950s during dengue epidemics in the Philippines and Thailand.

Today, severe dengue which affects most Asian and Latin American countries has become a leading cause of hospitalisation and death among children and adults in these regions.

Dengue which is considered the most significant mosquito borne disease after Malaria (Malaria was eradicated from Sri Lanka in 2016) is caused by a virus of the Flaviviridae family and there are four distinct, but closely related, serotypes of the virus that cause dengue, DEN-1, DEN-2, DEN-3 and DEN-4.

DEN-2 serotype was identified in laboratory tests as the circulating strain during 2017 outbreak. But WHO says, ‘All four DENV have been co-circulating in Sri Lanka for more than 30 years and DENV-2 has been infrequently detected since 2009.’

‘Recovery from infection by one provides lifelong immunity against that particular serotype. However, cross-immunity to the other serotypes after recovery is only partial and temporary. Subsequent infections (secondary infection) by other serotypes increase the risk of developing severe dengue.’

Due to improved care the health system has been effective at keeping the fatalities in check since the highest number of dengue deaths, 350 in 2009.

Source : WHO