Samitivej Hospital Update: COVID-19

 

How long can the virus survive on a solid surface? In other words, is it safe to touch a door handle, BTS bar, push a lift button, etc.?

There are 2 main ways of COVID virus transmission. First, there is direct respiratory transmission by droplets (postilions, sneezing, coughing). It is therefore important that potentially sick people wear a mask, sneeze into their elbow and keep at least a meter away from people who cough or sneeze. Second, there is transmission via contact: Coronavirus is a fragile virus in the environment. It can only survive a few hours on an inert surface: subway bar, coins, elevator button... The lifespan of the virus on an inert surface – with estimations ranging from few hours to 2 or 3 days - depends closely on the temperature, the residual humidity, the presence of biological fluid (postilions, sputum...) and the amount of virus it contains.

Let's take a concrete example: a person with coronavirus inadvertently sneezes into his hands and then touches an inert surface: BTS bar, coins, elevator button.... If a healthy person then touches this surface, he/she can theoretically contaminate his/her hands in a transient way. But, and this is a key point, several conditions must still be met to be infected: touching your face, putting your fingers in your nose, rubbing your eyes.... Even if the hands are contaminated, washing your hands properly will wipe out the virus and have no impact on your health.

There is a risk of contact contamination but the major risk is through direct respiratory breathing by inhaling the droplets of a person who sneezes or spits near you.

What would the studies say?

A first study on the subject has been published this week. The author James Lloyd-Smith said: “This virus has the capability or remaining viable for days”. The study found that the virus had different survival times depending on the surface:

  • Up to 72 hrs on hard surfaces such as plastic or stainless steel
  • Up to 24 hrs on cardboard
  • Only about 4 hrs on copper
  • In the air for up to 3 hrs

Other factors such has temperature, humidity and light affect the survival time.

Remark: This study has not yet (March 16, 2020) been peer reviewed. You can find it at the following link: https://www.medrxiv.org/content/10.1101/2020.03.09.20033217v1.full.pdf 

If you think a surface may be infected, clean it with simple disinfectant to kill the virus and protect yourself and others. Clean your hands with an alcohol-based hand rub or wash them with soap and water. Avoid touching your eyes, mouth, or nose.

Does the outside temperature play a role?

Possibly, but there is no conclusive scientific evidence at this point in time. 

The case for: a study, by a team from Sun Yat-sen University in Guangzhou, suggested heat had a significant role to play in how the virus behaves. “Temperature could significantly change Covid-19 transmission,” it said. “And there might be a best temperature for viral transmission.” What we know for sure is that is that ultraviolet light can be a really powerful disinfectant and we get a lot of UVA light from the sun. Direct sunlight can help rapidly diminish infectivity of viruses on surfaces. The other reason is that the strands of RNA of the virus are encased in lipids. Colder temperatures mean that the lipids are harder, providing more protection while the virus is outside of a host on a surface or in aerosolized droplets. Hotter temperatures break that coating down and may help to limit the virus' ability to spread.

The case against: the above mentioned study wasn’t peer reviewed and its results should be considered with caution. A 2nd study (also not peer reviewed), by a group of researchers from Harvard’s T.H. Chan School of Public Health found that sustained transmission and rapid growth in infections was possible in a range of humidity conditions – from cold and dry provinces in China to tropical locations. “Weather alone, such as an increase of temperature and humidity as the spring and summer months arrive in the Northern Hemisphere, will not necessarily lead to declines in case counts without the implementation of extensive public health interventions,” said the studyAnother consideration is that we spend most of our time in a temperature controlled (air con) and closed environment (no UVA). 

Mike Ryan, executive director of the WHO’s health emergencies programme, is among a host of experts who urged people not to assume the epidemic would automatically subside in the summer: “We have to assume the virus will continue to have the capacity to spread.”

Teleconsultation service by Samitivej: https://www.samitivejhospitals.com/samitivej-virtual-hospital-sem/

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