askST: Can I get infected with Covid-19 from touching a contaminated surface?

A recent study in Australia found that the Covid-19 virus can remain infectious for 28 days on smooth surfaces.
A recent study in Australia found that the Covid-19 virus can remain infectious for 28 days on smooth surfaces.PHOTO: ST FILE

SINGAPORE - A recent study in Australia found that the Covid-19 virus can survive on banknotes, glass and stainless steel for up to 28 days. It can also remain infectious for 28 days on smooth surfaces such as plastic and mobile phone screens.

The Straits Times outlines the implications of these findings, and the precautions people should take.

Q: What are the implications of this study?

A: It is important to keep in mind that these studies are performed under ideal conditions, where the temperature, light and humidity in the lab can be controlled.

Dr Danielle Anderson, scientific director of the Duke-NUS Medical School ABSL3 laboratory, said that in the real world, virus transmission from a surface to a person can be disturbed.

For example, if an MRT pole has been contaminated, virus particles can be transferred to the hands of someone who touches it. But if this person sanitises his hands afterwards, the virus can be killed, and the transmission is broken.

Professor Dale Fisher, a senior consultant at Division of Infectious Diseases at the National University Hospital, noted that transmission via contaminated surfaces does occur but it is not the dominant route. The studies demonstrate the possibility of such transmission, but do not prove it.

Q: What is the risk of being infected by touching surfaces that have been touched by an infected person?

A: Prof Fisher said that while it is difficult to quantify risk, there needs to be "adequate viable virus" for transmission to occur via a contaminated surface.

For instance, an individual would need to touch the contaminated surface, and then his eyes or mouth, but each movement would dilute the virus number.

Since the maximum amount of virus is in the throats of those infected, there will be less of the virus on surfaces they have touched, and even less in the next person's eyes and throat.

Direct droplet transfer from person to person will carry more of the virus and has a higher likelihood of transmission.

Q: Should I be worried about touching the same surfaces as an infectious person?

A: No, as the risk of transmission is very low, especially in Singapore, which has few community cases. For safety, people should still hold handrails on staircases and MRT trains, said Prof Fisher, but it is important to practise good hand hygiene.

People should continue to sanitise and wash their hands regularly, and avoid touching their face as much as possible.

Q: Should I avoid touching money?

A: No, as the risk of being infected from touching banknotes is low. But if you are worried, you can opt for contactless payment methods as much as possible.

Q: What safety precautions should I take when using my mobile phone?

A: Mobile phone screens tend to be dirty, simply because we use them all the time.

If there was an infected person touching surfaces on the train for instance, and you touch the same surfaces, and then use your phone before sanitising your hands, there is a possibility of the virus staying on the phone's surface, noted Dr Anderson.

To be safe, sanitise your phones with disinfectant wipes where possible, and avoid using them during meals.

Q: Should I be worried about going to the airport, and possibly touching the same surfaces as an infected person?

A: With travellers often mingling at the airport, there tends to be a higher risk of infection, but with surfaces regularly disinfected and people practising good hygiene, the risk is minimised, said Prof Fisher.

In addition, required testing at the time of travel and upon arrival in Singapore further helps to ensure that the risk of infecting others while in transit is low, said Dr Anderson. Even if the individual tests negative at first, and positive later on, they are unlikely to be shedding enough virus to be infecting others.