Spread of Adenovirus to Geographically Dispersed Military Installations, May–October 2007

Jill S. Trei; Natalie M. Johns; Jason L. Garner; Lawrence B. Noel; Brian V. Ortman; Kari L. Ensz; Matthew C. Johns; Michel L. Bunning; Joel C. Gaydos


Emerging Infectious Diseases. 2010;16(5) 

In This Article

Abstract and Introduction


In mid-May 2007, a respiratory disease outbreak associated with adenovirus, serotype B14 (Ad14), was recognized at a large military basic training facility in Texas. The affected population was highly mobile; after the 6-week basic training course, trainees immediately dispersed to advanced training sites worldwide. Accordingly, enhanced surveillance and control efforts were instituted at sites receiving the most trainees. Specimens from patients with pneumonia or febrile respiratory illness were tested for respiratory pathogens by using cultures and reverse transcription–PCR. During May through October 2007, a total of 959 specimens were collected from 21 sites; 43.1% were adenovirus positive; the Ad14 serotype accounted for 95.3% of adenovirus isolates. Ad14 was identified at 8 sites in California, Florida, Mississippi, Texas, and South Korea. Ad14 spread readily to secondary sites after the initial outbreak. Military and civilian planners must consider how best to control the spread of infectious respiratory diseases in highly mobile populations traveling between diverse geographic locations.


Adenovirus (Ad)–associated acute respiratory disease (AdARD) epidemics have been widely reported among recruits at US Department of Defense (DoD) training centers.[1–5] Vaccines targeting Ad4 and Ad7, the most common serotypes associated with these illnesses, were used among United States military trainees from 1971 through early 1999, when the supply was exhausted following cessation of vaccine production in 1996.[1] Because of the historically high negative effects of respiratory disease and the discontinuation of vaccine, the DoD initiated a population-based, active surveillance program in 1996 to track acute respiratory disease (ARD) activity among recruits at 8 military training centers, including the Air Force's only recruit training center at Lackland Air Force Base (AFB) in San Antonio, Texas.[1,6,7]

Lackland AFB admits 400–800 new basic military trainees (BMTs) per week; ≍35,000 BMTs graduate annually. BMTs are assigned to flights of 45–65 persons during the 6.5-week training program. All flight members train, eat, and sleep as a unit and are housed in 1 large open-bay facility. According to DoD surveillance data, during January 2005–January 2007 Lackland AFB experienced relatively mild ARD activity among BMTs; rates ranged from 0.1–0.7 cases per 100 recruit-weeks (US Naval Health Research Center, unpub. data). No adenovirus-positive specimens from Lackland AFB were serotyped during 2005, and only 4 were serotyped during 2006; serotypes included 1 Ad21, 1 AdC, and 1 Ad3. One specimen showed an Ad14/Ad21 co-infection.[8] Adenovirus serotype B14 (Ad14) was detected at Lackland AFB for the first time in 2006; in that same year, Ad14 was also detected at 3 other DoD training centers.[8]

Beginning in February 2007, an outbreak of respiratory illness associated with Ad14 occurred among Lackland AFB BMTs. During the height of the outbreak in June 2007, ARD rates exceeded 2.0 cases per 100 recruit-weeks (Naval Health Research Center, unpub. data). Most cases involved only mild, acute, febrile, respiratory illness. However, during April–October 2007, 27 patients were hospitalized with pneumonia and more severe sequelae; some patients required intensive care. All these patients were found to be adenovirus positive, and 20 (74.1%) had positive tests for the Ad14 subtype. The recognition of these more severe cases prompted an investigation and enhanced surveillance to describe the clinical and epidemiologic characteristics of Ad14 in this population. Laboratory results from early in the investigation indicated that 63% of ARD-related respiratory specimens collected from BMTs were positive for adenovirus and that 90% of adenovirus infections were the Ad14 subtype.[9] Most BMTs became ill with adenovirus in training weeks 4 and 5 (US Naval Health Research Center, unpub. data) and may have still been infectious after graduation because virus shedding can occur in respiratory secretions and feces for several weeks.[10–12]

We modeled the transmission of Ad14 through 2 hypothetical flights containing 50 BMTs each (Figure 1) by using data based on actual laboratory results and epidemiologic findings from Lackland AFB; our model indicated that >50% of BMTs, during the height of the outbreak, were infected with Ad14 over the course of the 6.5 week training period (9; Naval Health Research Center, unpub. data). At the end of basic training, with the conservative assumption that recovering patients shed virus for up to 1 month, ≍28% of BMTs were still infectious at graduation and in the following days or weeks. Given the likelihood that some BMTs were still ill or shedding Ad14 after completing basic training, response and control efforts had to account for the high mobility of this population.

Figure 1.

Evolving adenovirus subtype B14 incidence rate per 100 US Air Force basic military trainees over 6.5 weeks of basic training, based on epidemiologic and laboratory surveillance data. Red circles, acutely ill; yellow circles, recovering/possibly infectious; blue circles, well.

Following graduation, students immediately dispersed to >130 secondary DoD sites for advanced training (Figure 2); most went to a few large Air Force training centers in the United States, while a few went to smaller sites worldwide. Secondary training sites, including Sheppard AFB (Wichita Falls, TX, USA), Goodfellow AFB (San Angelo, TX, USA), and Keesler AFB (Biloxi, MS, USA), began reporting increased ARD among their trainees in mid to late May 2007. We report the spread of Ad14 to secondary training installations and subsequent response efforts, following the Lackland AFB outbreak, from May 25 through October 31, 2007.

Figure 2.

Locations of military sites that received US Air Force basic military training graduates for secondary training in North America (A), the Pacific region (B), and Europe and the Middle East (C). Red indicates locations that submitted specimens as part of adenovirus surveillance. Star in panel A indicates Lackland Air Force Base, Texas, USA. Maps generated by using TerraMetrics (www.terrametrics.com).