If there was an outbreak with thousands of cases we would know about it because a hospital would get a surge of cases * Coronavirus (COVID-19) has cases and transmission in warm countries now.
This long incubation period means that people can be unaware that they are sick for about a week, and there have been multiple reported cases of people transmitting the virus prior to the onset of symptoms.
A new study predicted that 46% of infected travelers will board planes with undetected infections, therefore limiting the effectiveness of airport screening and risking spread to other passengers and diverse locations.
Parameter values and assumptions for the baseline scenario estimating effectiveness of exit and entry screening at airports for detecting passengers infected with novel coronavirus (2019-nCoV).
Quarantine and contact tracing of symptomatic individuals alone may not be effective and early, strong control measures are needed to stop transmission of the virus.