COLOMBO, July 1 (Xinhua) -- Thirty five people died and over 23,000 were infected by the dengue virus across Sri Lanka in the first six months of this year, the Epidemiology Unit said here Monday.

Till the end of June, a total of 23,842 dengue cases were reported, with the highest number of cases reported from the Colombo district with 5,069 cases, followed by Gampaha in the outskirts of Colombo with 3,052 cases and Galle in the south with 2,031 cases.

With the ongoing rains, the Epidemiology Unit said it had identified five high risk districts which include Colombo, Gampaha, Galle, Kalutara in the Western Province and Ratnapura, in south central Sri Lanka.

Medical experts have urged people to seek immediate medical attention if they suffered from high fever, uncontrolled vomiting, abdominal pain, dizziness and reduced urinary.

"All fever patients need rest and should refrain from attending work or school," epidemiologists said.

"Dengue Hemorrhagic Fever (DHF) can be fatal," epidemiologists added.

Medical experts have further urged pregnant women to seek hospital admission immediately on the first day of fever.

Last year, over 50 people died and over 48,000 were affected by the dengue virus in Sri Lanka, with the National Dengue Control Unit launching several programs to eradicate dengue's breeding grounds in several districts of the island country.