RESUMO
The COVID-19 pandemic has caused a worldwide shortage of personal protective equipment including N95 and FFP3 respirators. Reusable elastomeric respirators are suitable alternatives when used with compatible filters. These filters may be difficult to source and elastomeric respirators are not recommended for surgical use as the exhaled air is not filtered. Breathing system filters are routinely used in anaesthetic circuits to filter virus and bacteria. In this study, we designed 3D printed adapters that allowed elastomeric respirators to utilise breathing system filters and made simple modifications to the respirators to filter exhaled breaths. We then evaluated the performance and safety of our modified elastomeric respirators with quantitative fit tests. We recruited 8 volunteers to perform quantitative fit tests. Fit factors, respiratory rate and end-tidal carbon dioxide were recorded before and after wearing the modified respirators for 1 hour. All 8 volunteers obtained fit factors of 200+, the maximum achievable, for all tests exercises in all fit tests. The mean (range) end-tidal carbon dioxide was 4.5 (3.9-5.5) kPa and 4.6 (range 4.1-5.3) kPa before and after 1 hour of usage. The mean (range) respiratory rate was 16.5 (11-24) min-1 and 17.4 (15-22) min-1 before and after 1 hour of usage. Four (50%) did not experience any subjective discomfort while 2 (25%) reported pressure on the face, 1 (12.5%) reported exhalation resistance and 1 (12.5%) reported transient dizziness with exertion. Breathing system filters combined with properly fitted reusable elastomeric respirators is a safe alternative to N95 during the COVID-19 pandemic.
RESUMO
Initial cases of COVID-19 reported in Hong Kong were mostly imported from China. However, most cases reported in February 2020 were locally-acquired infections, indicating local community transmissions. We extracted the demographic, clinical and epidemiological data from 50 COVID-19 patients, who accounted for 53.8% of the cases in Hong Kong by February 2020. Whole-genome sequencing of the SARS-CoV-2 were conducted to determine the phylogenetic relatedness and transmission dynamics. Only three (6.0%) patients required ICU admission. Phylogenetic analysis identified six transmission clusters. All locally-acquired cases harboured a common mutation Orf3a G251V and were clustered in two subclades in global phylogeny of SARS-CoV-2. The estimated time to the most recent common ancestor of local COVID-2019 outbreak was December 24, 2019 with an evolutionary rate of 3.04x10-3 substitutions per site per year. The reproduction number value was 1.84. Social distancing and vigilant epidemiological control are crucial to the containment of COVID-19 transmission. Article summary linesA combined epidemiological and phylogenetic analysis of early COVID-19 outbreak in Hong Kong revealed that a SARS-CoV-2 variant with ORF3a G251V mutation accounted for all locally acquired cases, and that asymptomatic carriers could be a huge public health risk for COVID-19 control.
