MANILA, Jan. 16 (Xinhua) -- The Philippine Department of Health (DOH) said on Thursday that four more polio cases have been detected, bringing the total number of cases to 16 since an outbreak was declared in September 2019.

Philippine Health Secretary Francisco Duque said two boys, aged two and three, from Maguindanao province, and a two-year-old boy Sultan Kudarat in the southern Philippines contracted the virus. Another three-year-old boy from Quezon City in the country's capital was also found positive of the virus, he said.

Duque said all the four boys "manifested with fever, diarrhea, muscle pain, asymmetric ascending paralysis and weakness of extremities."

The number of polio cases continues to rise despite the government's aggressive campaign to administer oral polio vaccines in Metro Manila and the southern Mindanao region.

"The outbreak must be put to a halt, and we can only do this if all our health facilities are achieving the targets for all AFP (acute flaccid paralysis) surveillance indicators, and if (synchronized anti-polio vaccination) reached the target population and vaccinated," Duque said.

Duque called parents and caregivers to have their children under five years old vaccinated during synchronized polio vaccination rounds.

"Additional polio doses can provide additional protection to your children," he said, adding that "there is no overdose with the oral polio vaccine."

The Philippines aims to accomplish 95 percent vaccination coverage in all areas that are at risk, including remote island provinces in the southern Philippines.

In September 2019, the Philippines declared a polio outbreak after the infectious disease reappeared 19 years after the country was declared polio-free by the World Health Organization in 2000.

The DOH announced a polio outbreak in the Philippines in September 2019, with the first type 2 poliovirus case found in Marogong town in Lanao del Sur in the southern Philippines.

On November 26, the DOH announced the re-emergence of type 1 poliovirus in Maluso town in Basilan island province also in the Philippine south.

Polio is an infectious disease that spreads rapidly. It can cause paralysis and, on rare occasions, can be fatal. There is no cure for polio. However, it can only be prevented with multiple doses of polio vaccines that have long been proven safe and effective.

It is spread when the stool of an infected person is introduced into the mouth of another person through contaminated water or food.

So far, immunization is the most effective way to protect children from polio and stop the spread of the virus.