Yearly trends in pulmonary tuberculosis (PTB), influenza, and pneumonia mortality per 100,000 people during the Russian and Spanish influenza pandemics in the city of Bern (A and C) and in Switzerland (B and D).

<p>Yearly trends in pulmonary tuberculosis (PTB), influenza, and pneumonia mortality per 100,000 people during the Russian and Spanish influenza pandemics in the city of Bern (A and C) and in Switzerland (B and D).</p

Relative excess pulmonary tuberculosis (PTB) mortality due to influenza, pneumonia, and combined diagnosis of influenza/pneumonia during the Russian (1889) and Spanish (1918) influenza pandemics.

<p>Relative excess pulmonary tuberculosis (PTB) mortality due to influenza, pneumonia, and combined diagnosis of influenza/pneumonia during the Russian (1889) and Spanish (1918) influenza pandemics.</p

Correlation between TB mortality according the total number of windows per apartment (Fig A) and the percentage of rooms without direct day light (Fig B) in the ten quarters of Bern, 1911–1915.

<p>Correlation between TB mortality according the total number of windows per apartment (Fig A) and the percentage of rooms without direct day light (Fig B) in the ten quarters of Bern, 1911–1915.</p

Modeling assumptions for infectious diseases incidence.

Estimated prevalence (cases per 100,000 people) of Mtb in the young (age group of the 15 to 24-year-olds) and the general population [42–44]. Estimated incidence (new cases per 100,000 people) of SARS-CoV-2 using a consistent approach (see Methods) based on estimates of excess mortality [47] and time-updated, country-specifc infection-fatality ratios [48]. Reported incidence (new cases per 100,000 people) of SARS-CoV-2 in the young age group of the 10 to 20-year-olds) of Switzerland [51] and in the general population of South Africa [50] and Switzerland [51]. Incidence of SARS-CoV-2 in Tanzania is not shown because it has barely been reported [45, 46].</p

Overview of study setting and collected data.

The COVID-19 pandemic renewed interest in airborne transmission of respiratory infections, particularly in congregate indoor settings, such as schools. We modeled transmission risks of tuberculosis (caused by Mycobacterium tuberculosis, Mtb) and COVID-19 (caused by SARS-CoV-2) in South African, Swiss and Tanzanian secondary schools. We estimated the risks of infection with the Wells-Riley equation, expressed as the median with 2.5% and 97.5% quantiles (credible interval [CrI]), based on the ventilation rate and the duration of exposure to infectious doses (so-called quanta). We computed the air change rate (ventilation) using carbon dioxide (CO2) as a tracer gas and modeled the quanta generation rate based on reported estimates from the literature. The share of infectious students in the classroom is determined by country-specific estimates of pulmonary TB. For SARS-CoV-2, the number of infectious students was estimated based on excess mortality to mitigate the bias from country-specific reporting and testing. Average CO2 concentration (parts per million [ppm]) was 1,610 ppm in South Africa, 1,757 ppm in Switzerland, and 648 ppm in Tanzania. The annual risk of infection for Mtb was 22.1% (interquartile range [IQR] 2.7%-89.5%) in South Africa, 0.7% (IQR 0.1%-6.4%) in Switzerland, and 0.5% (IQR 0.0%-3.9%) in Tanzania. For SARS-CoV-2, the monthly risk of infection was 6.8% (IQR 0.8%-43.8%) in South Africa, 1.2% (IQR 0.1%-8.8%) in Switzerland, and 0.9% (IQR 0.1%-6.6%) in Tanzania. The differences in transmission risks primarily reflect a higher incidence of SARS-CoV-2 and particularly prevalence of TB in South Africa, but also higher air change rates due to better natural ventilation of the classrooms in Tanzania. Global comparisons of the modeled risk of infectious disease transmission in classrooms can provide high-level information for policy-making regarding appropriate infection control strategies.</div

Cross-sectional mortality rates per 100,000 population of pulmonary tuberculosis (PTB) and influenza (including pneumonia and acute respiratory diseases) in Bern (A and C) and Switzerland (B and D) by age, during the influenza pandemics of 1889–1894 and 1918–1920.

<p>Cross-sectional mortality rates per 100,000 population of pulmonary tuberculosis (PTB) and influenza (including pneumonia and acute respiratory diseases) in Bern (A and C) and Switzerland (B and D) by age, during the influenza pandemics of 1889–1894 and 1918–1920.</p

Changes in the mortality due to injuries (including homicide), communicable (infectious diseases and infant death) and non-communicable diseases (including cancer) in the capital city of Bern, Switzerland, between1856 and 1950.

<p>Bars represent average 5-year mortality; the black curve represents tuberculosis (TB) mortality. Data were not available for the years 1868–1869, 1871 and 1926 to1928.</p

Carbon dioxide (CO₂) levels in the classrooms of schools in South Africa, Switzerland, and Tanzania.

Histogram of the measured CO2 levels (in parts per million [ppm]) in each country. All distributions are truncated at 400ppm (left) and 4,000ppm (right).</p

Excess death estimates and time-updated, country-specific infection-fatality ratios (IFRs) used to estimate the incidence of SARS-CoV-2.

Excess death estimates and time-updated, country-specific infection-fatality ratios (IFRs) used to estimate the incidence of SARS-CoV-2.</p

Seasonal trends in pulmonary tuberculosis (PTB) and influenza monthly mortality per 100,000 population.

<p>Seasonal trends in pulmonary tuberculosis (PTB) and influenza monthly mortality per 100,000 population.</p