South China's Guangdong Province reported 1,587 new cases of Dengue on Monday, bringing the total number of cases to 13,449, local health authorities said Tuesday.

A total of 11,309 cases had been reported in the provincial capital Guangzhou, the provincial health and family planning commission said in a press release.

Foshan, a manufacturing city neighboring the capital, reported 1,389 cases, while Shenzhen reported 36 cases, it said.

As of Monday, 19 out of 21 prefecture-level cities had reported dengue fever cases, the document said.

Four fatalities have been reported so far, three in Guangzhou and one in Foshan.

This year's outbreak, the worst in two decades, bodes ill for the National Day holiday that begins Wednesday, when many people travel.

Health authorities have attributed the outbreak to high temperatures and wet weather in Guangdong, where the mosquito population is five times the normal level.

Only 694 dengue fever cases were reported in Guangdong this time last year.

Dengue is a mosquito-borne, potentially fatal disease that affects between 50 and 100 million people in tropical and subtropical regions every year, causing fever combined with muscle and joint aches.