The main problem would be saving lives, finding these people to save, and preventing others from contacting those infected. Presently responses are to carry out tests on people passing by, which if not a mass exercise would be a waste of time due to those tested would need retesting soon afterward. It would be a waste of money also as we are not finding all those affected, you need a mass screen first to locate victims, then test these ones only, that would save money and time. This is obviously a global problem, so the concept would save people everywhere where a disease is spreading. Nearly everyone is at least threatened, many are affected. Detection methods have already been developed to detect temperature, low blood oxygen levels, most victims of any serious virus will show temperature, 90 percent of them. The low blood oxygen levels are a serious outcome of the Covid 19 virus, people do not notice any loss of oxygen, from breathing, but they can faint and die from low blood oxygen levels. For other viral infections there should be more research into symptoms that can be put into detection devices, for mass screening technology.