Warmer temps could slow spread
Flu usually dissipates as spring arrives
As coronavirus spreads, one common hope is that the coming warmer months may help slow the spread of the virus.
According to the Centers for Disease Control and Prevention, nearly 100,000 people had contracted the disease worldwide, as of Friday, including at least 164 in the United States.
While the disease is still poorly understood, Dr. Stefan Baral, an associate professor of epidemiology at Johns Hopkins University in Baltimore, speculates that warm weather behavior will be the primary driver behind a seasonal downturn.
“As we move into warmer weather and people are more out in the open, I expect there to be a natural decrease, similar and consistent with the decrease with other upper respiratory tract infections,” Baral said. “It’s more seasonal in nature. Obviously, it’s been a relatively warm winter, but as we’re outside more, we just expect less of those types of infections to take place.”
But Thomas Jaenisch, an associate professor of epidemiology at the University of Colorado School of Public Health, said he believes warmer and drier weather in particular is better correlated with stopping the spread — which might be at odds with Boston’s often humid summer climate.
“I think this is something that is reasonable to speculate,” Jaenisch said. “It’s based on pure physics. How long can those droplets be in the air and not fall down? This depends on how big the droplets are, the ambient temperature, the moisture.”
“The idea is when it is dry and hot, then these droplets fall down faster. When it is moist and colder, then the droplets can stay in the air suspended and can be taken in by another human,” Jaenisch said. “But, we don’t really know enough about the features of the virus to really be sure.”
It is believed that the virus is spread through airborne droplets from coughing or sneezing, direct contact with an individual with the virus, or contact with traces of virus left on commonly touched surfaces.
“Many of these viruses are transmitted by droplet or by direct contact. The mix of these two transmission pathways is a factor that determines the transmissibility in a given climate,” Jaenisch said. “The droplet airborne transmission is more effective in a cold, moist climate.”
New England’s summer climate varies somewhat from the warmer, drier weather that Jaenisch speculates could stall the disease. But Baral said, “What we don’t know is if there’s anything different with this virus in terms of contagiousness … it’s really the next few months that are going to be pretty fundamental in terms of having the right public health interventions in place to prevent local transmissions.”
This spring and summer could also, perhaps, be trending a bit warmer than usual for New England and most of the United States. The Climate Prediction Center’s late spring and summer outlook covering May, June and July puts all of Massachusetts and New England in its zone of aboveaverage temperatures.
“Trends and most (computer) models favor above normal temperatures from the Mid-Atlantic, to the Gulf Coast and westward to the Four Corners and Pacific Coast states,” the CPC wrote in its long-term seasonal outlook.
With warmer weather ahead, though, it should be noted that the epidemiologists’ opinions on weather and the coronavirus are based on comparisons with other similar viruses. That could change as more is learned about this specific coronavirus.
“We are always trying to make comparisons with influenza, which we know much better,” Jaenisch said. “We need to realize that these comparisons are not well underpinned with data. So, we can speculate.”