No other recruits at the MCRD have shown symptoms or have been diagnosed with a meningococcal infection, Capt. John Malone, medical services director at Naval Medical Center San Diego, told the San Diego Union-Tribune.

It was purely chance that the two separate bacterial infections, meningococcal and step A, hit the recruit population at the same time, Malone said.

Other members of Pvt. Miguel Zavala's platoon received a special oral antibiotic the day he died that should safeguard them against the bacteria, Malone said.

Doctors did not give the antibiotic, called levofloxacin, to all 4,500 recruits and depot staff because no one else showed symptoms of the rapidly moving infection that killed Zavala, Malone said.

Recruits in other platoons and the public are not at risk because the bacteria is only spread to others in the same living area, Malone said.

"You have to be in the same household," Malone told the Union-Tribune. "You don't get it by just walking across the parade ground."

All recruits entering MCRD are vaccinated against the meningococcal bacteria, but the vaccine is not always effective, Malone said.

One recruit remains in critical condition from the step A-related pneumonia outbreak that struck the depot.

More than 126 people were hospitalized with pneumonia, though not all were related to strep A.