"It's not if, but when. With water all over the place you get dengue, chikungunya, Zika," he said.
Lopez and four other doctors from Florida Hospital in Orlando with Puerto Rican roots flew to the island Sept. 29 Friday to help hospitals to the south in Ponce and to the northwest in Aguadilla.
"We saw in two days five people die," said resident William Kotler, who was volunteering with the team.
He said they were still trying to get a generator to the hospital in Aguadilla to run the air conditioners.
"It's 90 degrees inside. People are becoming dehydrated," he said.
On Wednesday, the doctors took two U.S. Army helicopters to Jayuya, landing at the center of the town track, where stray horses roamed after the storm, to assess the hospital's needs and deliver medications in scarce supply, such as insulin, ibuprofen and acetaminophen.
"Many of these towns are so blocked, you need a helicopter to get to them," said Dr. Katia Lugo before consulting with staff at the 15-bed public Mario Canales Torresola Hospital.
They had another emergency: a patient with a severe head wound. Hilberto Torres Hernandez, 62, a retired mechanic, had been helping a neighbor repair her car after the storm, just as he had helped the mayor, when it fell and struck him.
Doctors couldn't reach the capital's Centro Medico to ensure they could receive Torres because the phones in Jayuya have been down since the storm. In some cases, staff has been transferring trauma patients to larger cities without knowing if they can accept them. So far, none have been turned away.
The volunteer doctors were able to borrow a satellite phone, call the hospital in San Juan and ensure that the man could be treated there.