The US Centers for Disease Control and Prevention (CDC) estimates that around 35% of novel coronavirus COVID-19 infections are asymptomatic.
In other words, people infected with the virus show no symptoms at all.
But according to Business Insider, new research suggests the 35% figure may actually be a conservative guess.
Studies of cruise ship passengers in Argentina and patients in Wuhan, China showed roughly half of those who tested positive showed symptoms.
Not only that, but the Wuhan study also showed those asymptomatic cases were only contagious for approximately half as long as those who had symptoms.
Researchers from the University of California - San Francisco say asymptomatic spread is the "Achilles heel" of coronavirus mitigation strategies.
In other words, without testing asymptomatic patients, the US might continue to struggle to contain its COVIC-19 outbreak.