Sri Lanka's dengue cases have now topped 100,000 – the worst-ever outbreak.
Health officials have attributed the current catastrophe to recent floods that have left pools of stagnant water and rotting rain-soaked rubbish lying around.
The Sri Lanka Red Cross Society and the International Federation of Red Cross and Red Crescent Societies said, on Monday, that they will be increasing emergency assistance.
"Dengue patients are streaming into overcrowded hospitals that are stretched beyond capacity and struggling to cope, particularly in the country’s hardest hit western province," the Red Cross/Red Crescent statement said.
Almost 300 people have died and aid agencies have warned about the possibility of the mosquito-borne disease continuing to spread.
"Dengue is endemic here, but one reason for the dramatic rise in cases is that the virus currently spreading has evolved and people lack the immunity to fight off the new strain," Novil Wijesekara, head of health at the Sri Lanka Red Cross said in a statement.
The Red Cross announced a budget increase of $300,000, while the ministry of health reports the number of deaths since the start of 2017 as 296. The figure is nearly double that of last year.
About half of the cases are reportedly from the western region of the country.
According to the World Health Organization, dengue is one of the world's fastest growing diseases, endemic in 100 countries, with as many as 390 million infections annually.
Last week, Australia pledged $1.2m to help with patient care and to stem the spread of the virus.