Quantifying superspreading for COVID-19 using Poisson mixture distributions.

The number of secondary cases, i.e. the number of new infections generated by an infectious individual, is an important parameter for the control of infectious diseases. When individual variation in disease transmission is present, like for COVID-19, the distribution of the number of secondary cases is skewed and often modeled using a negative binomial distribution. However, this may not always be the best distribution to describe the underlying transmission process. We propose the use of three other offspring distributions to quantify heterogeneity in transmission, and we assess the possible bias in estimates of the mean and variance of this distribution when the data generating distribution is different from the one used for inference. We also analyze COVID-19 data from Hong Kong, India, and Rwanda, and quantify the proportion of cases responsible for 80% of transmission, [Formula: see text], while acknowledging the variation arising from the assumed offspring distribution. In a simulation study, we find that variance estimates may be biased when there is a substantial amount of heterogeneity, and that selection of the most accurate distribution from a set of distributions is important. In addition we find that the number of secondary cases for two of the three COVID-19 datasets is better described by a Poisson-lognormal distribution.

Bronchiolitis in COVID-19 times: a nearly absent disease?

Stay-at-home orders, physical distancing, face masks and other non-pharmaceutical interventions (NPIs) do not only impact COVID-19, but also the dynamics of various other infectious diseases. Bronchiolitis is a clinically diagnosed viral infection of the lower respiratory tract, and causes a yearly seasonal wave of admissions in paediatric wards worldwide. We counted 92,5% less bronchiolitis hospitalisations in Antwerp before the expected end of the peak this year (of which only 1 RSV positive), as compared to the last 3 years. Furthermore, there was a >99% reduction in the number of registered RSV cases in Belgium.Conslusion: The 2020 winter bronchiolitis peak is hitherto nonexistent, but we fear a 'delayed' spring/summer bronchiolitis peak when most NPIs will be relaxed and pre-pandemic life restarts. What is known? • Bronchiolitis causes a yearly seasonal wave of admissions in paediatric departments worldwide. • Non-pharmaceutical interventions (NPIs) do not only impact COVID-19, but also the dynamics of various other infectious diseases. What is new? • The 2020 winter bronchiolitis peak is hitherto nonexistent. • A 'delayed' spring or summer bronchiolitis peak could happen when most NPIs will be relaxed and pre-pandemic life restarts.

Exposure to cough aerosols and development of pulmonary COVID-19.

We hypothesized that most patients with severe pulmonary COVID-19 were exposed to cough aerosols. Among patients that were almost 100% certain which person infected them, only 14 out of 38 overall, and 9 out of 25 hospitalized patients requiring supplemental oxygen, were infected by someone who coughed, which did not support our hypothesis. Talking, especially with a loud voice, could be an alternative source generating SARS-CoV-2 aerosols. Further research is needed to determine how SARS-CoV-2 spreads. Avoiding to talk when you are not wearing your mask and not talking with a loud voice, 'voice etiquette', could be other public health interventions worthwhile exploring.