Ira Longini, a biostatistician and adviser to the World Health Organization, has bad news for those of you envisioning an epidemic-free summer. He predicts that two-thirds of the global population may eventually contract COVID-19, the new coronavirus, which originated in Wuhan, China. His models show that even if public health officials manage to decrease transmission by 50%, that would still leave roughly one-third of the world population infected—though he notes that many cases seem to be mild.
Experts have observed that COVID-19 transmission currently seems to resemble seasonal flu, which infected 45 million Americans in 2017-2018, despite 37% of the population getting flu shots. A COVID-19 vaccine is at least a year away. “Trying to stop influenza in a community without vaccine is like trying to stop the wind,” Dr. Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota, told The New York Times. “I don’t know how we’re going to stop this.”
A pivotal variable for accurate modeling is how many people each sick person infects, which is called the R0. (Let us help you sound smart this weekend: it’s pronounced “R-zero”, not “ro” or “r-oh.”) Current R0 estimates for COVID-19 are at 1.5-3.5 people; pinpointing the actual figure will dramatically change outbreak models. A great summary of COVID-19 modeling is here.
Longini’s work assumes an R0 of 2-3, and no successful vaccine or containment measures. “Surveillance and containment can only work so well,” he says. “Isolating cases and quarantining contacts is not going to stop this virus.”
It’s early days still. One bright spot so far has been Africa, which has been notably spared, with no reported cases so far. Experts say that this could be due to lack of testing capabilities, or the fact that flu-like illnesses tend to not take hold in Africa’s warm climates, or luck. Fingers crossed for us all.