There has been tremendous controversy recently about the "Asymptomatic Patient" - who are they and can they spread Coronavirus infection?

To understand the terminology in its context, let us look at three different but closely related situations - 

1. The Mildly Symptomatic Patient- This patient confirmed Covid-19 has mild symptoms like fever, occasional cough, or mild breathlessness. They gradually recover without any specialized treatment. 

2. The Pre-Symptomatic Patient-  These patients have been recently infected, have currently no symptoms, but will gradually develop them. They can transmit infection during this incubation period. This is usually about a week from contracting the infection but could be up to two weeks.

3. The Asymptomatic Patient - This is a confirmed case of Covid-19 who never develops any symptom.

What makes this disease pursue a relentless and fatal path in some patients and leaves many practically untouched is still a mystery. It could be related to the presence of ACE-2 receptors, strong innate immunity, infection with a low viral load, etc-  but we do not know for sure.

What makes these above three categories of patients worth serious consideration is that they could be the source of the global spread of the infection.

It is a logical question as to if a patient is asymptomatic how do we even know that they have Covid-19? 

These are usually seen when household contacts and others are traced back from a confirmed case. When one of them turns positive they are asked for symptoms - many such confirmed contacts claim to have no symptoms at all. Also, persons routinely tested before elective procedures (Dialysis, Chemotherapy), Air Crew, ship Crew, etc.

It was also seen onboard the ship Diamond Princess where passengers were extensively tested that many were asymptomatic or showed very mild symptoms. In the US Naval ship, Theodore Roosevelt, of the 600 sailors detected to be positive, more than half showed no symptoms.

Can an Asymptomatic Patient transmit the Virus? 

As per our current understanding of the disease not only do Presymptomatic and Asymptomatic patients spread the virus through droplets and contact, the virus also tends to linger longer in them. 

It is also seen that infectivity is higher during the first few days of contracting the infection.

The Lesson for us is simple. Treat every stranger on the street/ market as a Covid-19 patient and take precautions accordingly. Stay 2 meters away, wear a good mask, and restrict your movement out of the home. Move out only for necessary work or purchases. Do not organize or participate in get-togethers.