Coronavirus infections in Malta are likely to be spreading at a rate of 1.5 for every infected person, Superintendent for Public Health Charmaine Gauci said on Tuesday.
The estimated R0 (pronounced ‘R-Nought’) of 1.5 means that, on average, each person infected with COVID-19 transmits the virus to 1.5 other people. That calculation of the virus’ contagiousness emerges from modelling carried out by public health authorities as they try to contain the spread of COVID-19.
Malta’s estimated R0 compares favourably to the World Health Organization's estimate, made back in January when the virus was contained to Wuhan, China, that it had an R0 of 1.4 to 2.5. Other studies had estimated it even higher, at anything between 2.24 to 3.58.
Globally, Gauci said, researchers believe that the novel coronavirus has an R0 of 2.2 – meaning that, on average, every infected person spreads the virus to 2.2 more people.
Countries and public health experts must work to bring the R0 down to below 1. With an R0 of 1 or less, a virus has nowhere to spread and is gradually choked out.
Calculating a virus’ R0 is extremely difficult because it is not fixed: the value changes as societies adapt and react. Social distancing and other such measures intended to starve the virus of new hosts help bring that number down; people living in crowded conditions or inadequate use of personal protective equipment by healthcare workers, for instance, will bump the number up.
What the lower R0 means
Should local models be correct, Malta's R0 of 1.5 suggests that restrictions introduced to slow the spread of the virus - from closing borders to shutting down non-essential shops - are bearing fruit.
But given that the R0 is not fixed and depends in large part on human behaviour, that can quickly change if people disregard public health orders by, for instance, meeting in large groups.
Gauci has previously said that local authorities are basing their virus models on those of Hong Kong and has repeatedly warned that Malta has not yet reached the peak of its coronavirus infection curve.
A model devised by academics at the University of Washington’s UW Medicine earlier this month predicted that Malta will see its peak on April 22 and estimated that anything between two and 122 people would die of the virus locally.
The researchers have since updated their calculations. As of Wednesday, that model - which assumes full social distancing - predicted Malta's peak to be on April 29, with anything between three and 344 deaths.
Gauci has urged people to treat modelling data with caution, as all models are built on assumptions which may not turn out to be true in reality.
Malta had nine newly-confirmed coronavirus cases on Tuesday, bringing its total number of confirmed cases up to 393. Three patients have died so far, while 44 have recovered.