Wuhan, the ground zero of the COVID-19 epidemic has a cool, temperate climate with an annual average temperature around 15 degrees Celsius. Qom, the epicenter of the outbreak in the Middle East also has an arid, desert and cold climate with the annual temperature averaging 15 to 18 degree Celsius. The average temperature of Lombardy, Italy where bulk of the cases in Europe is concentrated also ranges between 7 degrees Celsius to 17 degrees Celsius. Daegu, the worst hit region in South Korea shares similar climatic characteristics with the other regions. Coincidentally or not, all of these regions lie between the latitudinal stretches ranging from 30 degree north to 45 degrees north. (Table 1)
Table 1: Latitudinal positioning of worst hit areas along with number of fatalities
|Wuhan (Hubei)||30.5928° N||2641|
|Qom (Iran)||34.6416° N||22|
|Lombardy (Italy)||45.4791° N||12|
|Daegu (South Korea)||35.8714° N||13|
|Tokyo (Japan)||35.6762° N||3|
Source: Coronavirus disease 2019 (COVID-19) Situation Report-38, World Health Organisation (WHO).
Cold climate: An enabler?
Coronaviruses of all types tend to spread faster in colder, dryer climates which explains a lot about the current pattern of virulence and fatality of the virus. Temperature and humidity may be the most important factors protecting warmer countries from this epidemic. The CoVID 19 outbreak like the previous viruses , 229E, OC43 or the SARS 2003 epidemic have affected geographies across the world in the North Temperate Zone, mainly occurring in the winter months.
SARS (Severe Acute Respiratory Syndrome) 2003 and MERS (Middle Eastern Respiratory Syndrome) 2012 have been two of the recent novel Coronavirus strains to have wreaked havoc on human populations causing a large number of fatalities. The first reported cases of SARS emerged in February 2003 in China. It infected about 8000 people across 26 countries and resulted in 774 deaths with the majority of the cases in mainland China. The MERS 2012 cases were first reported in Saudi Arabia in September 2012 and since then about 2494 cases have been reported with 858 associated deaths. More than 90 per cent of the cases and deaths have been reported in Saudi Arabia (who.int-2 2019). The emergence of the disease in both these cases occurred close to the onset of winter.
COVID-19: Latitudinal Chronology
A first glance at the global spread of COVID 19 would appear to be completely random but a second, closer look at the proliferation of reported cases unveils a pattern. The virus has spread to multiple countries, 54 at this moment but has proven to be especially lethal in about 4-5 counties. Let us take Wuhan, the original source of the virus on one side and Hong Kong on the other. The epidemic has resulted in about 65596 cases and 2641 deaths in Hubei while there have been 91 cases and 2 fatalities in Hong Kong. Preventive measures and quarantine are huge factors but the difference in the climate of the two cities is a major factor in the containment of the spread of the virus. Regions sharing similar climatic characteristics like Daegu, South Korea or Qom, Iran are facing much more acute outbreaks despite the virus reaching these cities at a much later date. As summer approaches and the regions currently affected warm up, the virus might make a northward shift, which would put Europe, Russia, the USA and many other countries in the crosshairs of this deadly pandemic.
Bats to be blamed?
The primary host of the SARS virus is understood to be bats which affected the civet cats. Humans most likely contracted the virus from civet cats. Bats were the animal reservoir for the MERS virus as well while dromedary camels were the animal source for human infections. Preliminary evidence suggests that the COVID-19 might have also originated from bats and jumped to humans through an intermediary, perhaps the pangolin, like the previous cases.
Seasonality of Coronavirus
Experts like Dr Michael Skinner, Reader in Virology, Imperial College London are of the opinion that COVID-19 will eventually become seasonal and settle down to normal rates of transmission as seen in previous coronaviruses. However, there are no guarantees as to how this new strain will behave. Thus such predictions and estimations should not create a false sense of security. Warmer regions like South America, India and Africa need to prepare for a worst case scenario keeping in mind its poor healthcare systems.As the behaviour of the strain is not known and any laxity in taking preventive measures might have untoward consequences.
SARS outbreak contained worldwide (1). Available at: https://www.who.int/mediacentre/news/releases/2003/pr56/en/
Will warming spring temperatures slow the coronavirus outbreak? Available at: