South China’s Guangdong Province confirmed 11,867 dengue fever cases on Monday, according to the provincial health department.

The provincial health and family planning commission reported that the number has risen sharply this year, up by 1,690 percent compared to last year.

A fatality was reported on Sunday in the provincial capital of Guangzhou, bringing the death toll to four in the province, three of which occurred in Guangzhou where 9,991 cases have been reported. The other fatality was in adjacent Foshan city, where 1,254 cases were confirmed, according to the commission.

Shenzhen, the most prosperous city in the province, has had 27 Dengue cases, officials said.

The outbreak of the disease this year is believed to be the worst in 20 years.

As the country’s National Day holidays begin on Wednesday, the provincial government is urgently carrying out disinfectant to densely-populated areas, especially in shopping malls, parks and transportation hubs.