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In January 2021 the British Army conducted its largest overseas training exercise since the start of the COVID-19 pandemic, deploying 1164 service personnel over an 11-week period during the second wave of COVID-19 in the UK.1 2 The authors intend to review the mass asymptomatic COVID-19 PCR testing that was undertaken during a local COVID-19 outbreak.
The first service personnel presented with symptoms consistent with COVID-19 six days after arrival, isolating and returning a positive PCR result two days later.3
By day 9 there were 65 symptomatic cases, returning 16 positive PCR results. At this time, the host nation (HN) offered to perform PCR tests on all deployed service personnel, aiming to attenuate the outbreak and enable the continuation of training.
A single nasopharyngeal PCR test was conducted on 951 of the 1041 asymptomatic, eligible service personnel over a two-day period (day 10 and day 11). The remaining 123 service personnel who were not eligible were either in an alternate location (58) or symptomatic and previously tested (65). From the 951 tests, there were 885 negative results, two inconclusive results and 64 positive results. Retesting on the two inconclusive results returned one positive result and one negative result, giving a total of 65 positive results from 951 personnel. One person who tested positive declared symptoms at the time of testing. After testing, 679 service personnel were isolating; 549 as primary contacts, 81 as individuals who tested positive and 49 other symptomatic personnel. Genomic sequencing was performed on the first 20 positive PCR COVID-19 results, 16 (80%) returning as the B.1.1.7 (Kent) variant.
These results demonstrate the utility of asymptomatic mass testing in a young population during a COVID-19 outbreak as it enabled effective and targeted isolation, aiding in the control of a local spread.
The deployment operated a UK standard of predeparture PCR testing, but not UK-standard preflight isolation or quarantine on arrival. The spread could have been reduced further if all service personnel completed a predeparture isolation period of 10–14 days with serial PCR testing, rather than a four-day isolation and a single PCR test. These measures would have minimised the chances of COVID-19 being transported into theatre, reducing the necessity of the mass testing event.
In future overseas exercises or operations, these results will be difficult to replicate at this scale. We were in a unique position given very low vaccination rates among deployed troops and high testing capacity. The HN enabled the testing: providing facilities and manpower to enable high numbers of tests, transportation with temperature control and processing within the clinical timeframe.
Enhanced testing in this environment offered a unique opportunity to find and quarantine the asymptomatic COVID-19 cases and to prevent further spread within the enclosed areas of camp, by separating those who tested negative into different areas.
The authors recommend that asymptomatic testing for COVID-19 can control outbreaks by aiding in early diagnosis and isolation of asymptomatic individuals. This is particularly relevant in an enclosed, largely young, fit and healthy population.
Patient consent for publication
Contributors MH initiated the idea and wrote the paper. DP, DC and AW reviewed the paper.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Provenance and peer review Not commissioned; internally peer reviewed.