A teenage girl is brought to hospital in Carmen de Bolivar, Bolivar Province, Colombia, after fainting on September 2, 2014

A mystery illness is plaguing girls in this town in northern Colombia, and locals say a vaccine against the sexually transmitted human papillomavirus, or HPV, is to blame.

First their hands and feet feel cold. Then they go pale and cannot move. Some convulse and fall to the floor.

In El Carmen de Bolivar, near the port of Cartagena, dozens of teenagers have experienced similar symptoms. Some have even lost consciousness.

"They vaccinated me in May and I started fainting in August. My legs became heavy and I couldn't feel my hands anymore. When I woke up, I was in the hospital," recalled 15-year-old Eva Mercado.

She passed out seven times in a month.

For most of the families affected in this town of 67,000, there is no doubt about what is causing the problem.

They place the blame squarely on a vaccination campaign against HPV, one of the most common sexually transmitted diseases, which can trigger cervical cancer.

The city's modest Nuestra Senora del Carmen hospital has been overwhelmed by a surge of unconscious teenage girls being wheeled through its doors.

Panicked fathers bring their daughters to the facility aboard their motorcycles, using the town's dirt roads.

Doctors search, in vain, for possible cases of hypoglycemia or drug abuse.

According to hospital official Augusto Agamez, about 370 minors have checked into the facility. There was also one boy among them.

"There is no diagnosis or specific treatment," Agamez told AFP, stressing that the hospital was also helping families cope with the unknown illness.

When they come to, the young patients learn breathing techniques from nurses.

They also receive saline solution and oxygen. Once back on their feet, the girls go home -- until the next spell.

- 'Not collective hysteria' -

"They brought me to the hospital 16 times last month," said Beatriz Martinez.

For the 15-year-old, it all started with headaches and backaches. Then her legs and hands gave in as well, forcing her mother to help her take baths.

The teenage girls affected by the mysterious malaise no longer go outside. Some don't even leave their homes.

"My daughter is not the same," said street vendor Jhon Jairo Mercaco, adding that, until now, his daughter had not been hospitalized since birth.

"I am desperate," said William Montes, a farmer who traveled down a mountain with his two daughters in a hammock to get them treated in town.

The epidemic has grabbed national headlines, and President Juan Manuel Santos has been forced to weigh in.

Insisting the HPV vaccination campaign was safe, Santos suggested the epidemic was no more than a "phenomenon of collective suggestion."

Those comments were met with tremendous anger in El Carmen de Bolivar, already shaken by Bogota's decades-long battle against the leftist Revolutionary Armed Forces of Colombia (FARC).

In the 1980s, clashes pitting government forces against the leftist rebels killed about 100 people here.

US drug giant Merck, which makes the Gardasil vaccine, said it was "confident in the safety profile" of its product.

"We continue to monitor adverse events reporting and are following this situation closely," it said in a statement to AFP.

"Merck/MSD will continue to support the ministry's immunization and monitoring efforts in Colombia."

Health Minister Alejandro Gaviria was met with boos and burned tires during a recent visit.

While promising a series of measures -- gathering data on patients, setting up new tests, providing psychological counseling -- the minister stopped short of suspending the vaccinations.

"We have no reason to stop at this time," Gaviria said.

Those words failed to reassure parents whose family and professional life have been upended by an illness whose origins are still unknown.

"This is not collective hysteria or manipulation. If you see your daughter have these symptoms after a vaccination, what else would you blame?" asked Maria Veronica Romera, the mother of a weakened 13-year-old.