The beginnings of the rainy season brought a spike in the number of children with respiratory disease. A few youngsters have died of complications from respiratory syncytial virus.
The virus shows symptoms like a cold in older children, but those under 1 who have other medical problems are particularly vulnerable.
The Hospital Nacional de Niños said over the weekend it is being flooded with serious cases.
The usual procedure is to put a child on oxygen, and hospital staffers are trying to bring in respirators from other locations.
A 2009 study reported in the The New England Journal of Medicine said that the infection frequently becomes bronchiolitis in patients under the age of a year.
Hospitalization lasted from two to 26 days in a group of 564 children that was studied in detail, the report said, adding that there was no death associated with the study group.
Nearly all had labored breathing, it said.
Infection does not seem to provide strong immunity, and some children have the disease multiple times. The airborne virus is so widespread that all children eventually have bouts of the respiratory syncytial virus.