MANILA (2nd UPDATE) -- The Department of Health on Monday declared a national dengue alert due to the rapidly-increasing number of cases of the mosquito-borne disease in several regions.

Under a national dengue alert, public hospitals, health centers, and local government units must be prepared with medicine, equipment and personnel to respond to dengue cases.

In a statement, the DOH said it recorded 106,630 dengue cases nationwide from Jan. 1 to June 29, an 85 percent increase from the 57,564 reported during the same period last year.

Western Visayas recorded the most cases with 13,164, followed by Calabarzon (11,474), Central Visayas (9,199), Soccsksargen (9,107), and Northern Mindanao (8,739).

The regions which exceeded the epidemic threshold are Mimaropa, Western Visayas, Central Visayas, and Northern Mindanao, according to the DOH.

The health department said it was also monitoring the following regions after exceeding the alert threshold: Ilocos region, Cagayan Valley, Calabarzon, Bicol region, Eastern Visayas, Zamboanga Peninsula, Davao, Bangsamoro Autonomous Region in Muslim Mindanao, and Cordillera Administrative Region.

Dengue is the world's fastest-growing infectious disease, afflicting hundreds of millions of people worldwide. It causes half a million life-threatening infections and kills about 20,000 people, mostly children, annually.

The disease has no known vaccine or specific antibiotics, the DOH said.

Signs and symptoms of dengue include severe headache, pain behind the eyes, severe joint and muscle pain, fatigue, nausea, vomiting, and skin rashes, according to the DOH.

The government in late 2017 stopped the sale of dengue vaccine Dengvaxia and its use in the state immunization drive after French maker, Sanofi, disclosed that it can trigger more severe symptoms for those who have not had dengue.

Authorities disagree publicly over whether Dengvaxia, the first of its kind, could have contributed to the deaths of several children.

The issue has spawned a drop in immunization coverage in the country to 40 percent last year, from an average 70 percent in recent years. -- Report from Jaehwa Bernardo and Apples Jalandoni, ABS-CBN News