Sweeping testing of the entire crew of the coronavirus-stricken US aircraft carrier Theodore Roosevelt may have revealed a clue about the pandemic: the majority of positive cases so far are among sailors who are asymptomatic, officials say.

The navy’s testing of the entire 4800-member crew of the aircraft carrier — which is about 94% complete — was an extraordinary move.

Roughly 60% of more than 600 sailors who tested positive so far have not shown symptoms of COVID-19, the navy says. 

The service did not speculate about how many might later develop symptoms or remain asymptomatic.