Lockdown did not appear to be linked with death rate
Covid-19 Mortality: A Matter of Vulnerability Among Nations Facing Limited Margins of Adaptation
We tested major indices from five domains (demography, public health, economy, politics, environment) and their potential associations with Covid-19 mortality during the first 8 months of 2020. Higher Covid death rates are observed in the [25/65°] latitude and in the [−35/−125°] longitude ranges. The national criteria most associated with death rate are life expectancy and its slowdown, public health context (metabolic and non-communicable diseases (NCD) burden vs. infectious diseases prevalence), economy (growth national product, financial support), and environment (temperature, ultra-violet index). Stringency of the measures settled to fight pandemia, including lockdown, did not appear to be linked with death rate.
Effects of Environmental Factors on Severity and Mortality of COVID-19
We examined the disease progression of COVID-19 in 6,914 patients admitted to hospitals in Europe and China. Meta-analysis of the mortality risk in seven European hospitals estimated odds ratios per 1-day increase in the admission date to be 0.981 (0.973–0.988, p < 0.001) and per increase in ambient temperature of 1°C to be 0.854 (0.773–0.944, p = 0.007). Statistically significant decreases of comparable magnitude in median hospital stay, probability of transfer to the intensive care unit, and need for mechanical ventilation were also observed in most, but not all hospitals. Severity of COVID-19 in Europe decreased significantly between March and May and the seasonality of COVID-19 is the most likely explanation.
Ten scientific reasons in support of airborne transmission of SARS-CoV-2
First, superspreading events account for substantial SARS-CoV-2 transmission; indeed, such events may be the pandemic's primary drivers. Second, long-range transmission of SARS-CoV-2 between people in adjacent rooms but never in each other's presence has been documented in quarantine hotels. Third, asymptomatic or presymptomatic transmission of SARS-CoV-2 from people who are not coughing or sneezing is likely to account for at least a third, and perhaps up to 59%, of all transmission globally and is a key way SARS-CoV-2 has spread around the world, supportive of a predominantly airborne mode of transmission. Fourth, transmission of SARS-CoV-2 is higher indoors than outdoors and is substantially reduced by indoor ventilation.
Indoor Air Changes and Potential Implications for SARS-CoV-2 Transmission
SARS-CoV-2 is primarily transmitted from the exhaled respiratory aerosols of infected individuals. Larger droplets (>100 μm) can settle out of the air due to gravitational forces within 6 feet, but people emit 100 times more smaller aerosols (<5 μm) during talking, breathing, and coughing. Smaller aerosols can stay aloft for 30 minutes to hours and travel well beyond 6 feet.1 Second, high-profile and well-described SARS-CoV-2 outbreaks across multiple space types (eg, restaurants, gyms, choir practice, schools, buses) share the common features of time indoors and low levels of ventilation, even when people remained physically distanced.
Covid-19 has redefined airborne transmission
People infected with SARS-CoV-2 produce many small respiratory particles laden with virus as they exhale. Some of these will be inhaled almost immediately by those within a typical conversational “short range” distance (<1 m), while the remainder disperse over longer distances to be inhaled by others further away (>2 m). Traditionalists will refer to the larger short range particles as droplets and the smaller long range particles as droplet nuclei, but they are all aerosols because they can be inhaled directly from the air. If we accept that someone in an indoor environment can inhale enough virus to cause infection when more than 2 m away from the original source—even after the original source has left—then air replacement or air cleaning mechanisms become much more important. This means opening windows or installing or upgrading heating, ventilation, and air conditioning systems, as outlined in a recent WHO document. People are much more likely to become infected in a room with windows that can’t be opened or lacking any ventilation system.