Lessons learned from the investigation of a COVID-19 cluster in Creil, France: effectiveness of targeting symptomatic cases and conducting contact tracing around them.

BACKGROUND: This study presents the methods and results of the investigation into a SARS-CoV-2 outbreak in a professional community. Due to the limited testing capacity available in France at the time, we elaborated a testing strategy according to pre-test probability. METHODS: The investigation design combined active case finding and contact tracing around each confirmed case with testing of at-risk contact persons who had any evocative symptoms (n = 88). One month later, we performed serology testing to test and screen symptomatic and asymptomatic cases again (n = 79). RESULTS: Twenty-four patients were confirmed (14 with RT-PCR and 10 with serology). The attack rate was 29% (24/83). Median age was 40 (24 to 59), and the sex ratio was 15/12. Only three cases were asymptomatic (= no symptoms at all, 13%, 95% CI, 3-32). Nineteen symptomatic cases (79%, 95% CI, 63-95) presented a respiratory infection, two of which were severe. All the RT-PCR confirmed cases acquired protective antibodies. Median incubation was 4 days (from 1 to 13 days), and the median serial interval was 3 days (0 to 15). We identified pre-symptomatic transmission in 40% of this cluster, but no transmission from asymptomatic to symptomatic cases. CONCLUSION: We report the effective use of targeted testing according to pre-test probability, specifically prioritizing symptomatic COVID-19 diagnosis and contact tracing. The asymptomatic rate raises questions about the real role of asymptomatic infected people in transmission. Conversely, pre-symptomatic contamination occurred frequently in this cluster, highlighting the need to identify, test, and quarantine asymptomatic at-risk contact persons (= contact tracing). The local lockdown imposed helped reduce transmission during the investigation period.

Long-Term Consequences of Spirometry During Military Routine Medical Examinations on Smoking Cessation Compared to Minimal Advice.

BACKGROUND: Smoking kills 8 million people a year worldwide. It is the most prevalent cause of death in France by cancer, cardiovascular, or respiratory diseases. Minimal advice consists in asking patients who smoke if they are interested in quitting. It is effective in reducing smoking. The French High Health Authority recommends its systematic use with patients, whatever their reason for seeking treatment. The beneficial effect of spirometry on smoking cessation is controversial. The objective of our study was to measure the consequences of spirometry associated with minimal advice, compared with only minimal advice in soldiers seen during a routine medical examination. METHODS: Our prospective, longitudinal, open, multicenter, controlled, randomized study was conducted among French military smokers presenting for an occupational medicine visit. Each participant received, depending on their group (intervention or control), either minimal advice associated with an evaluation of lung function by mini-spirometer, or only minimal advice. Follow-up visits were performed at 6 and 12 months. The primary objective was self-reported tobacco use cessation at 6 months. RESULTS: A total of 267 participants (126 in the intervention group and 141 for the control arm) were included in 10 centers between June 2019 and June 2020. The response rate was 75.6% at 6 months. The cessation rates were 17% and 18% in the intervention and control groups, respectively, with no significant difference between the two groups (P = 0.9). The cessation rate in the general population was 13% at 6 months. CONCLUSIONS: Spirometry does not seem to influence smoke cessation on a military population at 6 months. The overall cessation rate in our study was well in excess of the 3-6% expected from only providing minimal which is underused in general practice and should be encouraged.