Exhaled Mycobacterium tuberculosis output and detection of subclinical disease by face-mask sampling: prospective observational studies

Williams, Caroline; Abdulwhhab, Mohamad; Birring, Surinder S.; Kock, Elsabe de; Garton, Natalie J.; Townsend, Eleanor; Pareek, Manish; Al-Taie, Alaa; Pan, Jia-Yu; Ganatra, Rakesh; Stoltz, Anton; Haldar, Pranabashis; Barer, Michael R.

doi:10.1016/s1473-3099(19)30707-8

Cited by 109 publications

(117 citation statements)

References 29 publications

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“…is biologically plausible that milder cases are less transmissible, for example, because of an absence of cough 16,28 , but direct evidence is limited 49 and viral load is high in both clinical and subclinical cases 36 . If those with no or mild symptoms are efficient transmitters of infection compared with those with fully symptomatic infections, the overall burden is higher than if they are not as infectious.…”

Section: Nature Medicinementioning

confidence: 99%

Age-dependent effects in the transmission and control of COVID-19 epidemics

Davies

Klepac

Liu

et al. 2020

Nat Med

1,680

1,746

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The COVID-19 pandemic has shown a markedly low proportion of cases among children 1-4. Age disparities in observed cases could be explained by children having lower susceptibility to infection, lower propensity to show clinical symptoms or both. We evaluate these possibilities by fitting an age-structured mathematical model to epidemic data from China, Italy, Japan, Singapore, Canada and South Korea. We estimate that susceptibility to infection in individuals under 20 years of age is approximately half that of adults aged over 20 years, and that clinical symptoms manifest in 21% (95% credible interval: 12-31%) of infections in 10-to 19-year-olds, rising to 69% (57-82%) of infections in people aged over 70 years. Accordingly, we find that interventions aimed at children might have a relatively small impact on reducing SARS-CoV-2 transmission, particularly if the transmissibility of subclinical infections is low. Our age-specific clinical fraction and susceptibility estimates have implications for the expected global burden of COVID-19, as a result of demographic differences across settings. In countries with younger population structures-such as many low-income countries-the expected per capita incidence of clinical cases would be lower than in countries with older population structures, although it is likely that comorbidities in low-income countries will also influence disease severity. Without effective control measures, regions with relatively older populations could see disproportionally more cases of COVID-19, particularly in the later stages of an unmitigated epidemic. COVID-19 shows an increased number of cases and a greater risk of severe disease with increasing age 5,6 , a feature shared with the 2003 SARS epidemics 7. This age gradient in reported cases, which has been observed from the earliest stages of the pandemic 1 , could result from children having decreased susceptibility to infection, a lower probability of showing disease on infection or a combination of both, compared with adults. Understanding the role of age in transmission and disease severity is critical for determining the likely impact of social-distancing interventions on SARS-CoV-2 transmission 8 , especially those aimed at schools, and for estimating the expected global disease burden. Here, we disentangle the relative contributions of three potential drivers of the observed distribution of clinical cases by age. We present a summary of the main findings, limitations and implications of this work in Table 1. First, age-varying susceptibility to infection by SARS-CoV-2, where children are less susceptible than adults to becoming infected on contact with an infectious person, would reduce cases among children. Decreased susceptibility could result from immune for predicted global burden and the effectiveness of control interventions. This question must be resolved to effectively forecast and control COVID-19 epidemics.

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Section: Nature Medicinementioning

confidence: 99%

Age-dependent effects in the transmission and control of COVID-19 epidemics

Davies

Klepac

Liu

et al. 2020

Nat Med

1,680

1,746

View full text Add to dashboard Cite

show abstract

“…Transmission from breathing, talking and sneezing is also possible, as well as transmission from contaminated surfaces. (31,(38)(39)(40)…”

Section: Comparison To Other Studiesmentioning

confidence: 99%

The contribution of asymptomatic SARS-CoV-2 infections to transmission - a model-based analysis of the Diamond Princess outbreak

Emery

Russell

Liu

et al. 2020

Preprint

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BackgroundSome key gaps in the understanding of SARS-CoV-2 infection remain. One of them is the contribution to transmission from individuals experiencing asymptomatic infections. We aimed to characterise the proportion and infectiousness of asymptomatic infections using data from the outbreak on the Diamond Princess cruise ship. MethodsWe used a transmission model of COVID-19 with asymptomatic and presymptomatic states calibrated to outbreak data from the Diamond Princess, to quantify the contribution of asymptomatic infections to transmission. Data available included the date of symptom onset for symptomatic disease for passengers and crew, the number of symptom agnostic tests done each day, and date of positive test for asymptomatic and presymptomatic individuals. FindingsOn the Diamond Princess 74% (70-78%) of infections proceeded asymptomatically, i.e. a 1:3.8 case-toinfection ratio. Despite the intense testing 53%, (51-56%) of infections remained undetected, most of them asymptomatic. Asymptomatic individuals were the source for 69% (20-85%) of all infections. While the data did not allow identification of the infectiousness of asymptomatic infections, assuming no or low infectiousness resulted in posterior estimates for the net reproduction number of an individual progressing through presymptomatic and symptomatic stages in excess of 15. InterpretationAsymptomatic SARS-CoV-2 infections may contribute substantially to transmission. This is essential to consider for countries when assessing the potential effectiveness of ongoing control measures to contain COVID-19. FundingERC Starting Grant (#757699), Wellcome trust (208812/Z/17/Z), HDR UK (MR/S003975/1)

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“…In The Lancet Infectious Diseases, Caroline Williams and colleagues have assessed the effectiveness of face-mask sampling as a diagnostic method for tuberculosis. 3 Their approach could be a possible solution to a patient-led test. Most participants were happy to wear a face mask overnight; however, interruptions for face-mask changes in the protocol led to withdrawals from the study.…”

Section: Face-mask Sampling or Sputum To Diagnose Lung Tuberculosis?mentioning

confidence: 99%

“…Data from Williams and colleagues' study are preliminary. 3 They studied 24 patients with known positive cultures in a 24-h longitudinal study and 20 patients with symptoms of tuberculosis in an active case-finding pilot study. Of the 20 patients in the pilot study, eight were thought to have tuberculosis after testing, of whom six were exclusively positive from face-mask sampling.…”

Section: Face-mask Sampling or Sputum To Diagnose Lung Tuberculosis?mentioning

confidence: 99%

“…Other aspects that could influence how well vaccines work include whether asymptomatic infections lead to transmission and illness, the extent by which vaccination reduces infectiousness, and the inherent susceptibility of the population to gastrointestinal viruses based on the presence or absence of histoblood group antigens. 3 Establishing drivers of transmission of both rotaviruses and noroviruses will allow for future optimisation of vaccination and other strategies to more efficiently control the high burden of disease associated with these pathogens.…”

mentioning

confidence: 99%

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