How That Happened?

Listening and watching to the NEWS about the asymptomatic nature of anybody infecting others of the virus...

Common sense will tell you that if you don't have the symptoms of any illness, disease or ailment then you are not sick. NO SYMPTOMS OF ANY DISEASE means no diagnosis. You have to call an expert Diagnostic Team for such. Otherwise to make diagnosis based on error or misdiagnosis is criminal.

Unless of course if you have information of tracking such individuals who you think are "infected" such as for example ONLY: Group of medical practitioners and health care workers traveled around the world on health care mission in certain places known as HOT SPOT for such contagious diseases and then returned home to their home country and practice what they preached and get into the workforce once again. Let say, they traveled to Egypt. They went inside the pyramid down through where curiosity led them to unearth the pharaohs and mummies. Some of them got bit with mosquitoes and right away showed signs of  red rashes on their skin. Assuming that's nothing but mosquitoes and the rashes can be treated with topical derma solution. What they never knew is once bit by infected mosquitoes, the virus can linger inside the body through the blood stream. Mosquitoes are really small pest of blood suckers. However, swarms of mosquitoes could ultimately lead to something else, like "viral transmission." It can have an "incubation period" where you don't show any sign of symptom aside from those skin rashes. So, let say you are one of those nurses got bit by infected mosquitoes and when you returned to the workplace you have vulnerable patients who are already sick of pre-existing diagnosis and then you infected them with that "virus." In other words, those nurses or medical practitioners could be the HOST of such virus.

Above information is just one of the example of transmission.

How could those healthcare workers the carrier and host without showing symptoms? What is their immunity? Health care workers had their "immunity" based on several vaccines and immunizations they had. First and foremost they are "health protected" by the company they worked for. Just like those military men and women who are sent to the battle, they had been  tested and subjected to many "injections." So, if ever they are infected, the growth of the virus in their body can repel or attract depends on how strong and healthy they are or the growth of virus is just slow and can be controlled.