Behavioural insights and attitudes on community masking during the initial spread of COVID-19 in Hong Kong.

INTRODUCTION: Community face mask use during the coronavirus disease 2019 (COVID-19) pandemic has considerably differed worldwide. Generally, Asians are more inclined to wear face masks during disease outbreaks. Hong Kong has emerged relatively unscathed during the initial outbreak of COVID-19, despite its dense population. Previous infectious disease outbreaks influenced the local masking behaviour and response to public health measures. Thus, local behavioural insights are important for the successful implementation of infection control measures. This study explored the behaviour and attitudes of wearing face masks in the community during the initial spread of COVID-19 in Hong Kong. METHODS: We observed the masking behaviour of 10 211 pedestrians in several regions across Hong Kong from 1 to 29 February 2020. We supplemented the data with an online survey of 3199 respondents' views on face mask use. RESULTS: Among pedestrians, the masking rate was 94.8%; 83.7% wore disposable surgical masks. However, 13.0% wore surgical masks incorrectly with 42.5% worn too low, exposing the nostrils or mouth; 35.5% worn 'inside-out' or 'upside-down'. Most online respondents believed in the efficacy of wearing face mask for protection (94.6%) and prevention of community spread (96.6%). Surprisingly, 78.9% reused their mask; more respondents obtained information from social media (65.9%) than from government websites (23.2%). CONCLUSIONS: In Hong Kong, members of the population are motivated to wear masks and believe in the effectiveness of face masks against disease spread. However, a high mask reuse rate and errors in masking techniques were observed. Information on government websites should be enhanced and their accessibility should be improved.

Differential fadE28 expression associated with phenotypic virulence of Mycobacterium tuberculosis.

Ability to persist in human macrophages is central to the virulence of Mycobacterium tuberculosis and is not invariable among various strains. Differential gene expression that is associated with phenotypic virulence may provide additional information of virulent genes involved in the pathogenesis of M. tuberculosis, which is not fully elucidated. Three hypervirulent strains of M. tuberculosis isolated from patients suffering with tuberculous meningitis were shown to grow more rapidly inside human macrophages in a previous study. In the current investigation, expression of 7 mycobacterial genes (fadE28, mce1A, mymA, acr, sigA, sugC, and Rv3723) of these strains during ex vivo macrophage challenge and in vitro acid shock was quantified by real-time PCR. Using rrs gene as a normalisation gene, fadE28 gene exhibited differential gene expression that is associated with phenotypic virulence, whereas the other 6 genes showed indistinguishable expression patterns. Up-regulation of fadE28 gene in the hypervirulent strains may account for virulence by increasing the efficiency of beta-oxidation, which is important for the persistence in macrophages as M. tuberculosis uses fatty acids preferably inside phagosome of macrophages. The fadE28 gene, together with its adjacent genes may also be critical in the process of lipid modification that could facilitate parasitism in human macrophages.

Molecular characterization of clinical isolates of Mycobacterium tuberculosis and their association with phenotypic virulence in human macrophages.

Among 125 clinical isolates of Mycobacterium tuberculosis collected in Hong Kong and Shanghai, China, between 2002 and 2004, IS6110 typing revealed that 71 strains (57%) belonged to the Beijing family. The intracellular growth of the strains in human peripheral blood monocyte-derived macrophages was measured ex vivo on days 0, 3, 6, and 10. Among all tested strains, three hypervirulent strains showed significant increases in intracellular growth after 10 days of incubation. With an initial bacterial load of 10(4) CFU, most of the clinical isolates and H37Ra (an avirulent strain) exhibited no intracellular survival on day 10, while the three hypervirulent strains together with H37Rv (a virulent strain) showed on average a two- to fourfold rise in CFU count. These three hypervirulent strains belonging to a non-Beijing family were isolated from patients suffering from tuberculosis meningitis. Cytokines secreted by gamma interferon-activated macrophages were measured daily after challenge with selected strains of M. tuberculosis. The levels of tumor necrosis factor alpha were elevated after 24 h of infection among all strains, but the levels were significantly lower among the three hypervirulent strains, whereas interleukin 10 (IL-10) and IL-12 were not detected. Results were concordant with the differential expression of the corresponding cytokine genes in activated macrophages, as monitored by real-time PCR. Our findings highlighted that these three hypervirulent strains may possess an innate mechanism for escaping host immunity, which accounts for their characteristic virulence in patients presenting with a more severe form of disease.