Easy. Turn cell phone off.
And yes, I know of the people who say it’s not really off. We an iPhone 7 Plus (can’t remember the iOS version) tested it once while at work using some RF gear one of our departments had. It was a boring Friday afternoon, so why not.
Conclusion - it’s off when it’s off.
There is a report out this morning that would render surveillance meaningless.
A study of 175 recovered patients by the University of Fudan found little or no antibody presence in the blood in about 1/3 of that sample. This is very bad. Only days or weeks will have passed since the patients were declared recovered.
If immunity is not retained to this virus then no vaccine will be of any use.
Taking out the battery is even a stronger version of “off”. ;-)