As coronavirus becomes pandemic, scientists ask if lines on the map hold the key to contagion's spread
The coronavirus pandemic that has infected more than 125,000 people around the world is concentrated in a "corridor" across the northern hemisphere, researchers said, as more studies focused on how temperature and humidity could be used to predict the spread of the contagion.
Despite worries that Southeast Asia may become a coronavirus hotspot after central China (where the Covid-19 outbreak started) because of their proximity and travel connections to the infection's epicentre, more countries and regions like South Korea, Japan, Iran, northern Italy and the northwestern United States may have to bear the heaviest burden.
"The establishment of community transmission has occurred in a consistent east-and-west pattern. The new [regional] epicentres of the virus were all roughly along the 30-50 degree [lines of latitude] north zone," according to a team of US and Iranian researchers.
Their work, made public this week on the Social Science Research Network (SSRN) and pending review by peer experts, said that common temperature and humidity factors in these locations may allow epidemiologists to anticipate where virus cases may become focused.
The study was part of wider efforts by scientists to understand which traits the new coronavirus shared with other human coronaviruses and flu viruses, which display strong winter seasonality.
Earlier, researchers from Sun Yat-sen University in Guangzhou, China, found that transmission of the coronavirus responsible for the Covid-19 disease was sensitive to temperature, with an optimum environment of around 8.72 deg C - a finding that concurred with the US-Iran researchers' observations.
Other researchers, including Marc Lipsitch of Harvard T.H. Chan School of Public Health in Boston, Massachusetts, said that transmission of the new coronavirus was sustained in a range of temperatures and humidity, and that people should not pin their hopes on weather alone for the epidemic to go away.
The US-Iranian researchers, led by Mohammad Sajadi of University of Maryland School of Medicine in Baltimore, said there was a "striking similarity" between conditions in locations inside the current outbreak corridor, with average temperatures in the five-to-11 deg C range and relative humidity of between 47 and 79 per cent.
"These locations also exhibit a commonality in that the timing of the outbreak coincides with a nadir in the yearly temperature cycle, " the study said. "[This is] perhaps pointing to increased risk of outbreaks with prolonged conditions in this [temperature] range."
The team said that none of the cities affected by the coronavirus reported minimum temperatures below zero deg C, which may be a low for the contagion.
Making reference to temperature data from last March and April, the study predicted that new community spread in the coming weeks could emerge in areas just north of the current corridor. This spread could include northeastern and Midwest US, British Columbia, the British Isles and northeastern China.
But the study added that if temperatures warmed rapidly, coupled with lower population density and a well-prepared medical response, the risks to these areas might be mitigated.
The weather factor was also supported in a separate study by researchers from Beihang University and Tsinghua University in Beijing, one that was also undergoing peer review and was released on SSRN this week.
The university researchers found both data samples of China and 14 other countries showed that in the early days of their respective outbreaks, areas with lower temperatures and lower humidity suffered more severe outbreaks than places that were warmer and where humidity was greater.
Drawing on Chinese data collected between Jan 20 and 23, when local governments around the country started reporting Covid-19 cases but before aggressive lockdown and quarantine measures were imposed, the Beihang-Tsinghua team projected that high temperature and relative high humidity could help cut transmission of the virus.