Rapid communications

Stability of Middle East respiratory syndrome
coronavirus (MERS-CoV) under different
environmental conditions
N van Doremalen1, T Bushmaker1, V J Munster (vincent.munster@nih.gov)1
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
Article submitted on 10 September 2013 / published on 19 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, nodecrease in stability was observed at 20°C – 40% RH.
These data suggest the potential of MERS-CoV to betransmitted via contact or fomite transmission due toprolonged environmental presence.
In 2012, a novel coronavirus termed Middle East respiratory syndrome coronavirus (MERS-CoV) emergedin the Middle East [1]. Limited human-to-human transmission of MERS-CoV has been observed [2-5] andcurrently no data are available on the modes of transmission. The occurrence of MERS-CoV as a respiratory
pathogen and the high viral loads detected in samples
from the lower respiratory tract of infected patients[6,7] suggests that MERS-CoV will be predominantly
shed during coughing and via exudates from the lower
respiratory tract. For influenza A virus it is shown thattransmission is linked to the viability of the virus under
different environmental conditions, such as temperature and humidity with a cool dry environment being themost favourable for transmission and either warm or
humid conditions being unfavourable [8]. 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 andhigh humidity, 30°C – 80% RH and low temperatureand 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 MERSCoV under the three tested environmental conditions
was respectively compared with that of influenza A
virus A/Mexico/4108/2009 (H1N1) originating from ahuman isolate obtained during the influenza A(H1N1)
pdm09 pandemic in 2009 [9]. The stability of the twoviruses in aerosols at 20°C with 40% or 70% RH was
also assessed and compared.
www.eurosurveillance.org

Environmental stability

MERS-CoV(isolate
HCoV-EMC/2012)
andA/
Mexico/4108/2009 (H1N1) virus were propagated andtitrated by end-point titration on VeroE6 cells (for
MERS-CoV) and Madin-Darby canine kidney (MDCK)
cells (for A/Mexico/4108/2009 (H1N1) virus) as previously described [9,10]. To determine the environmental stability of the two viruses, 100 μl of 106 tissue
culture infective dose 50 (TCID50) of MERS-CoV or A/
Mexico/4108/2009 (H1N1) virus was spotted in droplets of 5 μl on the surface of steel or plastic washers(McMaster-Carr, USA) and incubated at the desiredconditions in an environmental chamber (Caron, USA)for 10 and 30 minutes and 4, 8, 24, 48 and 72 hours.
Experiments were conducted in triplicate. For both
MERS-CoV and A/Mexico/4108/2009 (H1N1) virus, nodifferences in stability could be observed between
the plastic and steel surface, suggesting the plastic and steel surfaces did not affect the stability differentially (Figure 1, panels A and D). MERS-CoV virus
could still be recovered after 48 hours at the 20°C –40% RH condition, whereas for the other two conditions the virus remained viable for eight (30°C – 80%
RH) and 24 hours (30°C – 30% RH) respectively. For
A/Mexico/4108/2009 (H1N1) virus, no virus could berecovered after four hours at each environmental condition and no difference between the environmental
conditions was observed. The mean half-life valuesof MERS-CoV varied between 0.441822 and 0.973656
hours (five-parameter logistic model, R and R package
drc [11]), but were not found to be significantly different (Table). Due to the rapid decrease in viability of A/
Mexico/4108/2009 (H1N1) virus, half-life values could
not be calculated.

Aerosol stability

To study their respective aerosol stability, MERS-CoVand A/Mexico/4108/2009 (H1N1) virus were aerosolised at 20°C with 40% or 70% RH (Figure 2). Aerosol
experiments were performed using the AeroMP(Biaera Technologies, USA) aerosol management platform [12]. 106 TCID50/ml solutions of MERS-CoV and1

Figure 1
Viability over time of Middle East respiratory syndrome coronavirus (MERS-CoV) and A/Mexico/4108/2009 (H1N1) virus
under different environmental conditions

MERS-CoV
Virus titre (Log10TCID50/ml)

A

B

Plastic

6

5

5

4

4

3

3

2

2

1

1

0

0
0

A/Mexico/4108/2009 (H1N1) virus
Virus titre (Log10TCID50/ml)

C

Steel

6

1 2

24

36

48

60

7 2

20°C – 40% RH
30°C – 30% RH
30°C – 80% RH
Standard deviation

6

5

0

1 2

24

36

48

60

7 2

0

1 2

24

36

48

60

7 2

D6
5

4

4

3

3

2

2

1

1

0

0
0

1 2

24

36

48

60

Time (hours)

7 2Time (hours)

RH: relative humidity; TCID50: tissue culture infective dose 50.
106 TCID50 of MERS-CoV (isolate HCoV-EMC/2012) (panels A and B) or A/Mexico/4108/2009 (H1N1) virus (panels C and D) was spotted on plastic(panels A and C) or steel (panels B and D) surfaces, incubated at 20°C – 40% RH (blue); 30°C – 30% RH (green) and 30°C – 80% RH (red) andtitrated on VeroE6 cells (for MERS-CoV) or Madin-Darby canine kidney (MDCK) cells (for A/Mexico/4108/2009 (H1N1) virus).

A/Mexico/4108/2009 (H1N1) virus respectively were
aerosolised in triplicate for 10 minutes. Aerosols werecollected continuously during aerosolisation in tissue
culture media (10 ml, DMEM) with an All Glass Impinger(Ace Glass Inc., USA). Collected aerosols were analysed by quantitative real-time polymerase chain reaction (qRT-PCR) and by virus titration [10,13,14]. TCID50
equivalents were generated using a standard curve of
10-fold diluted MERS-CoV RNA of known concentration in the qRT-PCR. Viral genomic RNA levels in TCID50
equivalents, representative of total amount of virus
particles, were compared to TCID50 , representative of2

the amount of viable virus of either MERS-CoV or A/
Mexico/4108/2009 (H1N1) virus [13,14].
MERS-CoV decreased only 7% in viability at 40% RH,
whereas the viability at 70% RH decreased significantly with 89% (unpaired one-tailed Student’s t-test,
p=0.0045). The viability of A/Mexico/4108/2009(H1N1) virus decreased under both conditions with
95% for 40% RH and 62% for 70% RH respectively.
This decrease was found to be significant at 40% RH(p=0.0095), but not at 70% RH and did not differ significantly between the two conditions.
www.eurosurveillance.org

TableDecay of Middle East respiratory syndrome coronavirus(MERS-CoV) on plastic and steel surfaces at different
temperatures and percent humidity

Figure 2
Aerosol stability of Middle East respiratory syndrome
coronavirus (MERS-CoV) and A/Mexico/4108/2009(H1N1) virus under different relative humidity conditions*Surface type; temperature,
relative humidity

A

Standard
deviation

Plastic; 20°C, 40%

0.954523

1.110443

Plastic; 30°C, 30%

0.441822

0.345291

Plastic; 30°C, 80%

0.904005

4.6838

Steel; 20°C, 40%

0.940139

1.837771

Steel; 30°C, 30%

0.973656

0.31109

Steel; 30°C, 80%

0.641163

0.825395

Mean half-life was determined from three independent
experiments.

4

**
*

3
Virus titre (Log10)aMean half-life time of
MERS-CoV (hours)a2

1

020°C – 40%RH

Discussion

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 ina rapid loss of viability [19]. Although a comparison
between different experimental studies should beapproached cautiously, the relative stability of MERSCoV 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 oftransmission for MERS-CoV is currently unknown, thespread of MERS-CoV between people in close contact
www.eurosurveillance.org

B
4

Virus titre (Log10)

Since MERS-CoV emerged [1], an increasing number ofhuman cases have been identified in eight different
countries with a case-fatality rate of 50- to 60% [15].
Small clusters of cases with human-to-human transmission have occurred in the United Kingdom, France
and Italy. In these clusters, initial cases had a recent
travel history to the Middle East and subsequently
infected secondary cases [2-5]. In addition, the largest cluster with suspected human-to-human transmission of MERS-CoV has been observed in Saudi Arabia
and is epidemiologically linked to healthcare facilities,
suggesting nosocomial transmission [16]. The recent
identification of the potential circulation of MERS-CoVin dromedary camels could indicate that both zoonotic
and human-to-human transmission is involved in theongoing spread of MERS-CoV [17,18].

20°C – 70%RH

**

3

2

1

0
20°C – 40%RH

20°C – 70%RH

Virus titre in log10TCID50/ml
Virus genome copies log10TCID50 equivalents/ml
Error bars represent standard deviation.
* = p-value < 0.05; ** = p-value < 0.01.

TCID50: tissue culture infective dose 50.
106 TCID50/ml of MERS-CoV (panel A) and A/Mexico/4108/2009(H1N1) (panel B) were aerosolised and viability was determined bytitration on VeroE6 cells (for MERS-CoV) or Madin-Darby canine
kidney (MDCK) cells (for A/Mexico/4108/2009 (H1N1) virus), andcompared to TCID50 equivalents derived by quantitative real-timepolymerase chain reaction (qRT-PCR).
TCID50 equivalents were extrapolated from standard curves
generated by adding dilutions of RNA extracted from a MERS-CoVstock with known virus titre in parallel to each run.

3

settings suggest contact and fomite transmission
routes are most likely involved [2,3,16]. Knowledge
on the environmental stability of MERS-CoV does notprovide 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 hightemperature suggests that direct contact transmission,and not fomite transmission, in the Arabian Peninsula
would be the most likely route of zoonotic and humanto-human transmission in outdoor settings. The abilityof 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 oftransmission could be the most effective way to arrest
the further spread of MERS-CoV.
Acknowledgements
The authors would like to thank Drs. Bart Haagmans
and Ron Fouchier, Erasmus Medical Center, Rotterdam,
The Netherlands for providing MERS-CoV (isolate HCoVEMC/2012), Emmie de Wit and Matt Lackemeyer for excellent
technical assistance and helpful discussions, Anita Mora
for assistance with the figures and Kui Shen for assistancewith statistical analyses. This research was supported by
the Intramural Research Program of the National Institute ofAllergy and Infectious Diseases (NIAID), National Institutesof Health (NIH).

Conflict of interest
None declared.

Authors’ contributions
N.v.D. and V.J.M. conceived and designed the study, N.v.D.
and T.B. performed the experiments, N.v.D. and V.J.M. analysed the data, N.v.D. and V.J.M wrote the manuscript.

*Erratum
Figure 2 was corrected and replaced on 23 September 2013.

References1.

Zaki AM, van Boheemen S, Bestebroer TM, Osterhaus AD,
Fouchier RA. Isolation of a novel coronavirus from a man withpneumonia in Saudi Arabia. N Engl J Med. 2012;367(19):181420. http://dx.doi.org/10.1056/NEJMoa1211721. PMid:23075143.
2. Mailles A, Blanckaert K, Chaud P, van der Werf S, Lina
B, Caro V, et al. First cases of Middle East Respiratory
Syndrome Coronavirus (MERS-CoV) infections in France,
investigations and implications for the prevention of humanto-human transmission, France, May 2013. Euro Surveill.
2013;18(24):pii=20502. Available from: http://www.
eurosurveillance.org/ViewArticle.aspx?ArticleId=20502
PMid:23787161
3. The Health Protection Agency (HPA) UK Novel Coronavirus
Investigation team. Evidence of person-to-person transmission
within a family cluster of novel coronavirus infections, United
Kingdom, February 2013 . Euro Surveill. 2013;18(11):pii=20427.

4

Available from: http://www.eurosurveillance.org/ViewArticle.
aspx?ArticleId=20427
4. Bermingham A, Chand MA, Brown CS, Aarons E, Tong C,
Langrish C, et al. Severe respiratory illness caused by anovel coronavirus, in a patient transferred to the United
Kingdom from the Middle East, September 2012. Euro
Surveill. 2012;17(40):pii=20290. Available from: http://www.
eurosurveillance.org/ViewArticle.aspx?ArticleId=20290
5. Puzelli S, Azzi A, Santini MG, Di Martino A, Facchini M,
Castrucci MR, et al. Investigation of an imported case of
Middle East Respiratory Syndrome Coronavirus (MERSCoV) infection in Florence, Italy, May to June 2013. Euro
Surveill. 2013;18(34):pii=20564. Available from: http://www.
eurosurveillance.org/ViewArticle.aspx?ArticleId=20564.
PMid:23987829.
6. Drosten C, Seilmaier M, Corman VM, Hartmann W, Scheible
G, Sack S, et al. Clinical features and virological analysis
of a case of Middle East respiratory syndrome coronavirus
infection. Lancet Infect Dis. 2013;13(9):745-51.
http://dx.doi.org/10.1016/S1473-3099(13)70154-3
7. Guery B, Poissy J, el Mansouf L, Séjourné C, Ettahar N,
Lemaire X, et al. Clinical features and viral diagnosis of twocases of infection with Middle East Respiratory Syndrome
coronavirus: a report of nosocomial transmission. Lancet.
2013;381(9885):2265-72.
http://dx.doi.org/10.1016/S0140-6736(13)60982-4
8. Steel J, Palese P, Lowen AC. Transmission of a 2009 pandemic
influenza virus shows a sensitivity to temperature andhumidity similar to that of an H3N2 seasonal strain. J Virol.
2011;85(3):1400-2. http://dx.doi.org/10.1128/JVI.02186-10.
PMid:21084485. PMCid:PMC3020521.
9. Safronetz D, Rockx B, Feldmann F, Belisle SE, Palermo RE,
Brining D, et al. Pandemic swine-origin H1N1 influenza A virus
isolates show heterogeneous virulence in macaques. J Virol.
2011;85(3):1214-23.
http://dx.doi.org/10.1128/JVI.01848-10. PMid:21084481.
PMCid:PMC3020514.
10. de Wit E, Prescott J, Baseler L, Bushmaker T, Thomas T,
Lackemeyer MG, et al. The Middle East respiratory syndrome
coronavirus (MERS-CoV) does not replicate in Syrian hamsters.
PLoS One. 2013;8(7): e69127. http://dx.doi.org/10.1371/
journal.pone.0069127
PMid:23844250. PMCid:PMC3699510.
11. Ritz C, Streibig JC. Bioassay analysis using R. Journal of
Statistical Software. 2005;12(5):1-22.
12. Hartings JM, Roy CJ. The automated bioaerosol exposuresystem: preclinical platform development and a respiratory
dosimetry application with nonhuman primates. J Pharmacol
Toxicol Methods. 2004;49(1): 39-55.
http://dx.doi.org/10.1016/j.vascn.2003.07.001.
PMid:14670693.
13. Corman VM, Eckerle I, Bleicker T, Zaki A, Landt O, EschbachBludau M, et al. Detection of a novel human coronavirus by
real-time reverse-transcription polymerase chain reaction.
Euro Surveill. 2012;17(39):pii=20285. Available from: http://
www.eurosurveillance.org/ViewArticle.aspx?ArticleId=20285
14. Munster VJ, Baas C, Lexmond P, Bestebroer TM, Guldemeester
J, Beyer WE, et al. Practical Considerations for High-Throughput
Influenza A Virus Surveillance Studies of Wild Birds by Use of
Molecular Diagnostic Tests. J Clin Microbiol. 2009;47(3):66673.
http://dx.doi.org/10.1128/JCM.01625-08. PMid:19109483.
PMCid:PMC2650931.
15. World Health Organization (WHO). Global Alert and Response(GAR). Coronavirus infections. [Accessed 19 Sep 2013].
Available from: http://www.who.int/csr/don/archive/disease/coronavirus_infections/en/index.html
16. Assiri A, McGeer A, Perl TM, Price CS, Al Rabeeah
AA, Cummings DA, et al. Hospital Outbreak of Middle
East Respiratory Syndrome Coronavirus. N Engl J
Med. 2013;369(5):407-16. http://dx.doi.org/10.1056/
NEJMoa1306742. PMid:23782161.
17. Perera RA, Wang P, Gomaa MR, El-Shesheny R, Kandeil A,
Bagato O, et al. Seroepidemiology for MERS coronavirus
using microneutralisation and pseudoparticle virus
neutralisation assays reveal a high prevalence of antibody
in dromedary camels in Egypt, June 2013. Euro Surveill.
2013;18(36):pii=20574. Available from: http://www.
eurosurveillance.org/ViewArticle.aspx?ArticleId=20574
18. Reusken CB, Haagmans BL, Müller MA, Gutierrez C, Godeke GJ,
Meyer B, et al. Middle East respiratory syndrome coronavirus
neutralising serum antibodies in dromedary camels: acomparative serological study. Lancet Infect Dis. 8 Aug 2013.
[Epub ahead of print].
19. Chan KH, Peiris JS, Lam SY, Poon LL, Yuen KY, Seto WH. The
Effects of Temperature and Relative Humidity on the Viabilityof the SARS Coronavirus. Adv Virol. 2011;2011:734690.

www.eurosurveillance.org