Hi @Min just to clarify - what do you mean by 4th degree contact? The traditional use of the terminology refers to "degrees" of contact by rings of exposure i.e. if direct contact with a confirmed case - considered 1st degree exposure. If direct contact with an individual with 1st degree exposure but not with any confirmed case - considered 2nd degree exposure, and so on.

The asymptomatic individuals are monitored closely following the exposure to the "contact" for a duration equivalent to the incubation period of the virus in question. Should any 1st degree individual develop suggestion of infection during this time, he is reviewed by a medical professional immediately to determine the need for testing early. More information about this here: https://www.straitstimes.com/multimedia/a-guide-to-singapores-covid-19-contact-tracing-system

This serves as a method to focus contact tracing efforts and identify at-risk individuals. At the 4th degree, the risk from the index case is commensurately lower. However, in the event of an infection with community transmission, it is still possible to have contracted the infection from other cases. Therefore, it is not possible to say how likely it is for someone at the 2nd-3rd-or-4th degree of exposure to develop infection, only that those at the 1st degree are at significantly elevated risk.

Ultimately, the next step for you would be to resume life as per normal since you do not have symptoms, following MOH's guidelines for social distancing and hygiene to minimise your risk of catching the disease. If you do develop symptoms, have a low threshold to see your GP, or consider using Teleconsultation for a detailed initial discussion with a medical professional to determine the need to have a review in person. More about this here: https://www.todayonline.com/brand-spotlight/doctor-will-see-you-next-app

Hope this helps!