"We received reports that US hostage Martin Burnham is suffering from malaria," said Col. Alexander Aleo, commander of the Basilan-based 103rd Army Brigade.
"Martin is said to be trembling and chilling especially during nighttime, and these are symptoms of malaria," Aleo told Agence France Presse. "We are worried about his deteriorating health."
Burnham, his wife Gracia and 19 Filipinos were seized by Abu Sayyaf gunmen on May 27 last year from a beach resort in Palawan and brought to Basilan where the bandits seized hospital workers, including nurse Deborah Yap, from a local hospital.
US Special Forces have been advising Filipino troops fighting the Abu Sayyaf for four months without much success in Basilan.
"The US hostage has become frail because of the disease and the captive’s condition in the jungle," Aleo said, citing information gathered by military intelligence from Basilan eyewitnesses.
"The hostages and the kidnappers are highly mobile, making it extremely difficult for us to rescue the victims," he said.
Although US military presence has not directly resulted in the rescue of the Burnhams and Yap, the Armed Forces Southern Command (Southcom) said the joint RP-US "Balikatan 02-1" military exercises have stirred the "hornet’s nest" of terrorists here and abroad.
"This explains the arrests being made in many areas in the country and we are now able to monitor the activities of terrorist cells operating not only in Mindanao but also in Luzon," said Southcom spokesman Lt. Col. Danilo Servando.
"We are successful in this aspect of the operation," Servando added, stressing that the ongoing exercise has deterred the inflow of international terrorists who may be looking for safe havens because of the US-led international war against terrorism.
"We were able to prevent the inflow of would-be members of the al-Qaeda (terrorist) network who are fleeing the Middle East to establish bases in other areas," Servando said. - With a report from Roel Pareño