A national dengue epidemic has been declared in the Philippines, where 622 people have died of the mosquito-borne disease since January and millions more are at risk, CNN reports.

From the start of the year to July 20, there have been more than 146,000 cases recorded -- a 98% increase from the same time period last year, according to the country's Department of Health.

Dengue causes flu-like symptoms, including piercing headaches, muscle and joint pains, fever and full body rashes. Of the millions of people infected every year worldwide, an estimated 500,000 develop severe symptoms requiring hospitalization, and of those some 12,500 people die, according to the World Health Organization (WHO).

The Philippines had declared a national dengue alert just last month after reporting more than 450 deaths -- but officials had said the dengue was "localized," according to CNN affiliate CNN Philippines.

With almost two hundred additional deaths in the past month, the crisis has now escalated to a national epidemic.

The epidemic was declared in order to enable government agencies to better identify at risk areas, said a health ministry statement.

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"It is important that a national epidemic be declared in these areas to identify where a localized response is needed, and to enable the local government units to use their Quick Response Fund to address the epidemic situation," said Health Secretary Francisco Duque in the statement.

Epidemics have been declared in seven out of the country's 17 regions: Calabarzon, Mimaropa, Bicol, Western Visayas, Eastern Visayas, Zamboanga Peninsula, and Northern Mindanao. Together, these regions are home to more than 40 million people, about 40% of the Philippines population.

Several other regions like Central Visayas and Ilocos are at high risk with thousands of cases reported, though not yet past the epidemic threshold.

"As part of our data, is 5,100 cases per week average," said Duque at a press conference about the epidemic on Wednesday. "This is really staggering. This is going to be a record number."

Since July, health officials have worked to combat the spread of the viral infection. They deployed hundreds of doctors and nurses to provincial and district hospitals, and provided emergency funding to affected regions, among other measures, according to the Department of Health.