South China's Guangdong province is on high alert against the worst dengue fever outbreak in the past 20 years.

Local health authorities say 1,400 new cases have been reported in the past two days alone, bringing the total number to nearly 7,500 people, about 14 times the average in previous years.

The provincial capital is the hardest hit area, with more than 6,300 cases reported, including two deaths.

Liu Qiyong with the national disease control and prevention center says the local climate and geography boost the mosquito-borne infection.

"The province is in tropical and sub-tropical regions that are highly prone to the dengue disease. Rain is frequent. Puddles can be seen everywhere after the rains, providing a favorable environment for mosquito incubation and growth."

Meanwhile, Liu warns that the huge tourist inflow from neighboring countries, also under the dengue threat, may worsen the situation in Guangzhou.

"Guangzhou is an international city that sees massive foreigner inflows every day. Most of these people are from South and Southeast Asia where dengue fever also prevails. It makes it more difficult for us to contain the disease."

Liu is reminding people to pay attention if they show flu-like symptoms such as high fever, nausea and headaches, lest they miss their best treatment opportunity.

The main dengue symptoms also include rashes and backaches, while the hemorrhagic variant that causes severe internal bleeding is often fatal.

Health experts warn seniors with chronic diseases are more vulnerable to the virus.