Transmission dynamics and prospective environmental sampling of adenovirus in a military recruit setting

Abstract

Background: High levels of morbidity caused by adenovirus among US military recruits have returned since the loss of adenovirus vaccines in 1999. The transmission dynamics of adenovirus have never been well understood, which complicates prevention efforts.

Methods: Enrollment and end-of-study samples were obtained and active surveillance for febrile respiratory illnesses (FRIs) was performed for 341 recruits and support personnel. Environmental samples were collected simultaneously. Classic and advanced diagnostic techniques were used.

Results: Seventy-nine percent (213/271) of new recruits were seronegative for either adenovirus serotype 4 (Ad-4) or adenovirus serotype 7 (Ad-7). FRI caused by Ad-4 was observed in 25% (67/271) of enrolled recruits, with 100% of them occurring in individuals with enrollment titers <1 : 4. The percentage of recruits seropositive for Ad-4 increased from 34% at enrollment to 97% by the end of the study. Adenovirus was most commonly detected in the environment on pillows, lockers, and rifles.

Conclusions: Potential sources of adenovirus transmission among US military recruits included the presence of adenovirus on surfaces in living quarters and extended pharyngeal viral shedding over the course of several days. The introduction of new recruits, who were still shedding adenovirus, into new training groups was documented. Serological screening could identify susceptible recruits for the optimal use of available vaccines. New high-throughput technologies show promise in providing valuable data for clinical and research applications.

Table 1

Adenovirus-related illness among recruits in each squad bay

Table 2

Adenovirus serotype 4 (Ad-4) and adenovirus serotype 7 (Ad-7) serological results and subsequent outcomes

Figure 1

Proportion of susceptible recruits who developed an adenovirus serotype 4 (Ad-4)–positive febrile respiratory illness (FRI), total daily calibrated amplitude from all positive environmental samples, and date of late-entering Ad-4–positive recruits for each squad bay. Filled markers, left axis Proportion of susceptible recruits (Ad-4 titer <1:4) who developed a subsequent Ad-4–positive FRI, as determined by throat culture, for each squad bay and plotted against day of active surveillance. A dramatic increase in the proportion of recruits who developed an Ad-4–positive FRI is demonstrated for weeks 3 and 4. Empty markers, right axis Sums of calibrated amplitudes of each triangulation identification for the genetic evaluation of risks (TIGER)–positive sample found in the squad bay environment, plotted against day of active surveillance. In squad bay A, the days of highest calibrated amplitudes of the TIGER-positive samples in the environment tended to coincide with the days of highest culture-positive counts in the recruits. Throughout training, recruits are often added to squad bays already in training. The lowercase letters (“a,” “b,” and “c”) below dates on the X axis indicate Ad-4–positive recruits who were added to a squad bay. There were 3 such positive late enrollments in squad bay A (indicated by “a”), 4 in squad bay B (“b”), and 1 in squad bay C (“c”)

Table 3

Surface and air environmental-sample results as identified by the triangulation identification for the genetic evaluation of risks (TIGER) test

Table 4

Heterotypic cross-neutralization results