June 2 (UPI) -- The limited spread of COVID-19 at a U.S. military base shows public health measures -- screening, testing, quarantining, social distancing and contact tracing -- offer some protection, the U.S. Centers for Disease Control and Prevention said Tuesday.
Efforts to prevent outbreaks of the disease caused by the new coronavirus, SARS-CoV-2, among more than 10,000 new recruits arriving at the U.S. Air Force's Joint Base San Antonio-Lackland, Texas, succeeded in limiting total confirmed cases to five through seven weeks.
Three of the five cases ultimately were traced to the first recruit on base to be diagnosed, officials said.
The approaches used at the base could serve as a blueprint for other "congregate settings" like colleges and athletic programs, the CDC said.
"Transmission of symptomatic COVID-19 was successfully limited at a single military base with adequate resources to screen personnel and the ability to track the movement of all trainees," researchers wrote.
Starting March 1, during the first two weeks of basic training, Air Force medical personnel tested trainees only if they reported with symptoms of COVID-19 and either exposure to someone with a confirmed infection or a history of travel to a region with high virus transmission.
Trainees were tested according to CDC guidelines, officials said, and only two trainees were evaluated during the first two weeks. After March 16, trainees were tested only on those who reported symptoms.
On March 11, access to the base was limited to essential personnel and events, including graduation ceremonies, which typically draw family members from around the world. As of March 13, training instructors were placed under local area travel restrictions.
All new recruits who arrived at the base March 17 or later were quarantined for a two-week period in an area of the facility isolated from the trainees. All trainees were instructed to maintain a distance of at least 6 feet between one another, and "universal use" of cloth face coverings was introduced April 6.
Basic training at the base was shortened from the usual 8 1/2 weeks to seven weeks after the first trainee tested positive March 23. In April, the facility also stopped taking recruits from areas of the United States with higher community transmission of the virus, reducing the number of incoming trainees by approximately 40 percent.
In all, 345 trainees met criteria for COVID-19 testing, and 86 were evaluated during arrival quarantine. In addition to the five confirmed cases, testing identified five cases of rhinovirus or enterovirus, three cases of para-influenza, two cases of metapneumovirus and two cases of influenza B.
Public health officials at the base conducted contact tracing for all PCR-confirmed COVID-19 cases, which revealed links between four of the five cases. All five of the confirmed cases were men, and none of them required hospitalization or received drug treatment.
They were placed in isolation until they met the criteria for returning to training, researchers said.
"Factors contributing to lack of transmission likely included early implementation of mitigation strategies before the first case occurred, mobilization of non-medical personnel to assist in symptom screening, and flexibility of the military training staff to adjustments in programs and schedules," the authors wrote.
"The disciplined and highly structured environment and the population structure likely contributed to the success of the implemented interventions," they wrote.