Coronavirus – Credit CDC PHIL
# 7793
Although viruses are generally pretty fragile, we know that under the right environmental conditions, some of them can retain their integrity and infectivity for hours, days, or even weeks outside of a host organism. Temperatures, UV exposure, pH, humidity, and other factors can all effect how long a virus can remain viable in the environment.
We know, for instance, that temperature and humidity greatly affect the spread of influenza (see Influenza Virus Survival At Opposite Ends Of The Humidity Spectrum), which helps explain the seasonality of flu.
Today, Eurosurveillance Journal has published our first good look at the environmental stability of the MERS coronavirus, both on surfaces (fomites), and as an aerosol. The researchers describe their experiments thusly:
In this study, the stability of MERS-CoV (isolate HCoV-EMC/2012) was evaluated under three different environmental conditions: high temperature and low humidity, 30°C – 30% relative humidity (RH); high temperature and high humidity, 30°C – 80% RH and low temperature and low humidity, 20°C – 40% RH, to reflect a wide range of environmental conditions including an indoor environment (20°C – 40% RH). The stability of MERS-CoV under the three tested environmental conditions was respectively compared with that of influenza A virus A/Mexico/4108/2009 (H1N1) originating from a human isolate obtained during the influenza A(H1N1)pdm09 pandemic in 2009 [9]. The stability of the two viruses in aerosols at 20°C with 40% or 70% RH was also assessed and compared.
Their results are striking.
- While the Influenza A virus became non-viable on steel and plastic surfaces in less than 4 hours for all testing environments, the MERS virus survived 48 hours in the 20°C – 40% RH environment. Survival of the coronavirus at 30°C – 30% RH was 24 hours, and 8 hours at 30°C – 80% RH.
- As an aerosol, the MERS virus remained very stable at 20°C – 40% RH, while its viability decreased (89% – comparable to the Influenza A virus) at 20°C – 70% RH.
The bottom line, under favorable temperature and humidity conditions (such as you might find in an air conditioned hospital), the MERS virus survives quite well on surfaces, and in the air. This may help explain the high rate of nosocomial outbreaks we’ve seen in the Middle East.
While the route of infection with this virus has not been determined, this virus shows the kind of environmental hardiness that would be conducive for either fomite or droplet/aerosol (contact) transmission.
Here is a link to the NIAID study (and excerpts).
N van Doremalen1, T Bushmaker1, V J Munster (
)1
- Laboratory of Virology, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT, USA
Citation style for this article: van Doremalen N, Bushmaker T, Munster VJ. Stability of Middle East respiratory syndrome coronavirus (MERS-CoV) under different environmental conditions. Euro Surveill. 2013;18(38):pii=20590. Available online: http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=20590
Date of submission: 10 September 2013
The stability of Middle East respiratory syndrome coronavirus (MERS-CoV) was determined at 20°C – 40% relative humidity (RH); 30°C – 30% RH and 30°C – 80% RH. MERS-CoV was more stable at low temperature/low humidity conditions and could still be recovered after 48 hours. During aerosolisation of MERS-CoV, no decrease in stability was observed at 20°C – 40% RH. These data suggest the potential of MERS-CoV to be transmitted via contact or fomite transmission due to prolonged environmental presence.
<BIG SNIP>
DISCUSSION (Excerpt)
Here we show that compared to A/Mexico/4108/2009 (H1N1) virus, MERS-CoV remains viable for a longer duration in the environment. After four hours no viable A/Mexico/4108/2009 (H1N1) virus was detected in comparison to 8, 24 or 48 hours for MERS-CoV depending on environmental conditions (Figure 1, panels A and D). MERS-CoV was very stable in aerosol form at 20°C – 40% RH. The decrease in viability at 20°C – 70% RH (89%) was comparable to that of A/Mexico/4108/2009 (H1N1) virus.
Severe acute respiratory syndrome coronavirus (SARS-CoV) has been reported to stay viable for up to five days at 22 to 25°C and 40 to 50% RH and increase in temperature and humidity resulted in a rapid loss of viability [19]. Although a comparison between different experimental studies should be approached cautiously, the relative stability of MERS-CoV at 20°C – 40% RH and the rapid decrease in virus viability at higher temperatures and higher humidity suggests that MERS-CoV and SARS-CoV share relatively similar stability characteristics.
Although the route of transmission for MERS-CoV is currently unknown, the spread of MERS-CoV between people in close contact settings suggest contact and fomite transmission routes are most likely involved [2,3,16]. Knowledge on the environmental stability of MERS-CoV does not provide direct insights in the route of transmission; yet it does provide us with a better understanding for the potential of aerosol, contact and fomite transmission. The prolonged survival of MERS-CoV compared to A/Mexico/4108/2009 (H1N1) virus on surfaces increases the likelihood of contact and fomite transmission. However, the decrease in viability observed at high temperature suggests that direct contact transmission, and not fomite transmission, in the Arabian Peninsula would be the most likely route of zoonotic and human-to-human transmission in outdoor settings.
The ability of MERS-CoV to remain viable in an airborne state suggests the potential for MERS-CoV to acquire the ability to be transmitted via aerosols. In the absence of therapeutic and prophylactic intervention strategies for MERS-CoV, a thorough understanding of the routes of transmission could be the most effective way to arrest the further spread of MERS-Co
