Corona weather summer3/27/2023 ![]() Notably the Vietnam study looked at influenza-like illness, without distinguishing influenza from other types of pathogens. Subsequently it has been shown that epidemiological patterns are consistent with this lab data in the US and in Vietnam, among other study sites. For influenza, it has been elegantly shown in the lab that absolute humidity - the quantity of water vapor in the air - strongly affects flu transmission, with drier conditions being more favorable. In the winter, the outdoor air is colder, and the air is dryer usually both indoors and out. For some viruses, we have evidence for which factors are most important, for others, we have to extrapolate. Scientists have identified four factors that contribute to this phenomenon. To understand why, it helps to understand what we know about why many respiratory viruses are winter-seasonal in temperate regions like most of the USA. The other reason this is a myth is that seasonal viruses that have been in the population for a long time (like OC43 and HKU1) behave differently from viruses that are newly introduced into the population. Still, it is worth considering the analogy especially to OC43 and HKU1, which are SARS-CoV2’s closest relatives among the seasonal coronaviruses. So the first problem with this myth is that we don’t know whether those coronaviruses, which go by the evocative names like OC43, HKU1, 229E, and NL63, are good analogies for this virus. Predicting how a novel virus will behave based on how others behave is always speculative, but sometimes we have to do so when we have little else to go on. Myth 2: The “common cold” coronaviruses are seasonal, with little transmission in the summer, so SARS-CoV-2 will be too. The resurgence confirms that it was control measures that stopped transmission the first time. This resurgence was eventually linked to a case from the first wave. In Toronto, SARS resurged after the initial wave was controlled and precautions were discontinued. ![]() ![]() These worked well for SARS because those who were most infectious were also quite ill in a distinctive way - the sick cases were the transmitters, so isolating the sick curbed transmission. These involved isolating cases, quarantining their contacts, a measure of “social distancing,” and other intensive efforts. It was killed by extremely intense public health interventions in mainland Chinese cities, Hong Kong, Vietnam, Thailand, Canada and elsewhere. Myth 1: In 2003, SARS went away on its own as the weather got warmer. The short answer is that while we may expect modest declines in the contagiousness of SARS-CoV-2 in warmer, wetter weather and perhaps with the closing of schools in temperate regions of the Northern Hemisphere, it is not reasonable to expect these declines alone to slow transmission enough to make a big dent.īefore making the positive case for my assertions, let me start by busting some myths. Some have even suggested that the experience with SARS in 2003 provides evidence for this assertion. Several people, including the US president, have suggested that the novel coronavirus SARS-CoV-2 and the disease it causes, COVID-19, will go away on its own in the warmer weather that will come in the Northern Hemisphere in coming months. Professor of Epidemiology and Director, Center for Communicable Disease Dynamics, Harvard T.H. ![]()
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