During the first weeks of the spread of the COVID-19 pandemic, some hopefully estimated that the arrival of high temperatures in the northern hemisphere would end up reducing infections. The reason for this prediction is based on the fact that many respiratory viruses, such as rhinoviruses, spread much more easily in the face of less efficient antiviral defense of infected cells in cool temperatures. Many viruses that cause the common cold reproduce their life cycles better in cold temperatures.
However, months later, and with the pandemic devastating all countries in all latitudes, the temperature does not seem to be associated with the spread of the virus. To confirm this, an international study has just been published, published by the prestigious CMAJ ( Canadian Medical Association Journal ).
Instead, the study does conclude that school closings and other public health measures are having a positive effect.
According to Dr. Peter Jüni, Institute for Health Policy, Management and Evaluation, University of Toronto and St Michael’s Hospital, Toronto, Ontario: “Our study provides important new evidence, using global data from the COVID-19 epidemic, that these public health interventions have reduced epidemic growth ”.
Method
The Canadian study looked at 144 geopolitical areas , states and provinces in Australia, the United States and Canada, as well as several countries around the world, and more than 375,600 confirmed cases of COVID-19. China, Italy, Iran and South Korea were excluded from the study because the virus was declining in some cases, or in a full disease outbreak at the time of analysis in others.
To estimate epidemic growth, the researchers compared the number of cases on March 27 with the cases on March 20, 2020, and determined the influence of latitude, temperature, and humidity, also taking into account measurements such as closure. of schools, mobility restrictions and social distancing during the March 7-13 exposure period.
Finally, they found little or no association between latitude or temperature with epidemic growth of COVID-19 and a weak association between humidity and reduced transmission. The results, that warmer weather had no effect on the progression of the pandemic, surprised the authors: “We had done a preliminary study that suggested that both latitude and temperature could play an important role. But when we repeated the study under much more rigorous conditions, we got the opposite result. “
However, for the preparation of this study, the authors point to several limitations, such as differences in testing practices, inability to estimate actual rates of COVID-19, and compliance with social distancing.
Lifting social distancing, a measure that must be carefully weighed
The researchers concluded that public health measures, including school closings, social distancing and restrictions on large gatherings, had been effective. In this sense, Dr. Peter Jüni warns: “Our results are of immediate relevance since many countries, and some provinces and territories are considering facilitating or eliminating some of these public health interventions.”
According to Professor Dionne Gesink, co-author and epidemiologist at the Dalla Lana School of Public Health: “Summer is not going to make this go away. It is important for people to know. On the other hand, the more public health interventions a area, the greater the impact in slowing epidemic growth. These public health interventions are really important because they are the only thing that works right now to stop the pandemic. “
When deciding how to lift restrictions, governments and public health authorities must carefully weigh the impact of these measures against the potential economic and mental health harms and benefits.
Referencias:
‘Impact of climate and public health interventions on the COVID-19 pandemic: A prospective cohort study’. Peter Jüni, Martina Rothenbühler, Pavlos Bobos, Kevin E. Thorpe, Bruno R. da Costa, David N. Fisman, Arthur S. Slutsky and Dionne Gesink. CMAJ May 08, 2020 cmaj.200920; DOI: https://doi.org/10.1503/cmaj.200920
