A recent paper looks at how long coronaviruses can survive on various types of surfaces. It finds that the virus tends to persist longer in colder, more humid conditions. The authors also ask how we can destroy coronaviruses.

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Electron micrograph of the coronavirus that caused SARS.

The novel coronavirus, now officially known as COVID-19, has been making headlines since it first came to light, late in 2019. Spreading from China to 23 other countries, COVID-19 has now infected 45,171 people.

Because this version of the coronavirus is new to science, researchers are scrambling to understand how to treat infections, and how to ensure that the virus does not spread further.

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Scientists from the Greifswald University Hospital and Ruhr-Universität Bochum, both in Germany, recently compiled information from 22 studies on coronaviruses. Their work helps us understand how long coronaviruses survive on surfaces, and how people may be able to destroy them.

The authors initially compiled the information for inclusion in an upcoming textbook; but, author Eike Steinmann explains that “under the circumstances, the best approach was to publish these verified scientific facts in advance, in order to make all information available at a glance.”

Their work, which appears in The Journal of Hospital Infection, focuses on the coronaviruses responsible for two of the most recent outbreaks: severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS).

Their paper also draws information from studies that investigated veterinary coronaviruses, such as transmissible gastroenteritis virus (TGEV), mouse hepatitis, and canine coronavirus.

The first section of the new paper focuses on how long coronaviruses can survive on inanimate surfaces, such as tables and door handles. The authors show that, depending on the material and the conditions, human coronaviruses can remain infectious from 2 hours to 9 days.

At temperatures of around 4°C or 39.2oF, certain versions of the coronavirus could remain viable for up to 28 days. At temperatures of 30–40°C (86–104°F), coronaviruses tended to persist for a shorter time.

At room temperature, a coronavirus responsible for the common cold (HCoV-229E) persisted significantly longer in 50% humidity than 30% humidity. Overall, the authors conclude:

“Human coronaviruses can remain infectious on inanimate surfaces at room temperature for up to 9 days. At a temperature of 30°C [86°F] or more, the duration of persistence is shorter. Veterinary coronaviruses have been shown to persist even longer for 28 d[ays].”

When the scientists delved into the literature on the persistence of coronaviruses on different surfaces, the results were variable. For instance, the MERS virus persisted for 48 hours on a steel surface at 20°C (68°F). However, on a similar surface and at the same temperature, TGEV survived for up to 28 days.

Similarly, two studies investigated the survival of two strains of SARS coronavirus on a paper surface. One survived 4–5 days, the other for just 3 hours.

In the next section of their paper, the authors address the best way to inactivate coronaviruses.

They conclude that agents, including hydrogen peroxide, ethanol, and sodium hypochlorite (a chemical in bleach), quickly and successfully inactivate coronaviruses.

For instance, the authors write that “[h]ydrogen peroxide was effective with a concentration of 0.5% and an incubation time of 1 minute.”

After assessing the evidence, the authors conclude:

“Surface disinfection with 0.1% sodium hypochlorite or 62–71% ethanol significantly reduces coronavirus infectivity on surfaces within 1 min[ute] exposure time.”

Conversely, solutions of a biocide called benzalkonium chloride produced conflicting results; and chlorhexidine digluconate, which people use as a topical antiseptic, was ineffective.

The authors write that “[t]ransmission in healthcare settings can be successfully prevented when appropriate measures are consistently performed.” Handwashing, in particular, is critical.

They explain how, in Taiwan, “installing hand wash stations in the emergency department was the only infection control measure which was significantly associated with the protection from healthcare workers from acquiring the [SARS coronavirus].”

Although the studies the authors summarize in this review did not investigate COVID-19, they believe that the results are also likely to be relevant to this latest coronavirus. All the human coronaviruses that the research had investigated seem to be susceptible to the same chemical agents.