EID Journal: The Stability Of The Ebola Virus On Surfaces & In Fluids

October 15th  Outside Nina Pham’s Apartment

 

# 9998

 

One of the critical issues that emerged during the Ebola epidemic in Western Africa is how little we actually knew about the stability and persistence of the virus in the environment, and how that might vary across different climates and settings. 

 

Variations in temperature, humidity, duration and strength of UV exposure, the types of fluids (including their pH), and the types of surfaces were all potentially mitigating factors. 

 

Last August, a CDC Interim Guidance and FAQ (see Interim Guidance for Environmental Infection Control in Hospitals for Ebola Virus) had this to say about the research to date:

 

6. How long does the Ebola virus persist in indoor environments?

Only one laboratory study has been reported, which was done under environmental conditions that favor virus persistence. This study found that under these ideal conditions, Ebola virus could remain active for up to six days.¹ In a follow-up study, Ebola virus was found, relative to other enveloped viruses, to be quite sensitive to inactivation by ultraviolet light and drying; yet subpopulations did persist in organic debris.²

In the only study to assess contamination of the patient care environment during an outbreak, conducted in an African hospital under "real-world conditions," Ebola virus was not detected by either nucleic acid amplification or culture in any of 33 samples collected from sites that were not visibly bloody. Virus was detected on a blood-stained glove and bloody intravenous insertion site by nucleic acid amplification, which may detect nonviable virus, but not by culture for live, infectious virus.³ Based upon these data and what is known regarding the environmental infection control of other enveloped RNA viruses, the expectation is that with consistent daily cleaning and disinfection practices in U.S. hospitals, the persistence of Ebola virus in the patient care environment would be short, with 24 hours³ considered a cautious upper limit.

 

That said, the CDC adopted some very strict guidance on dealing with potential environmental contamination from the Ebola virus, outlined in Interim Guidance for the U.S. Residence Decontamination for Ebola Virus Disease (Ebola) and Removal of Contaminated Waste  and CDC Interim Ebola Guidance: Mortuary Removal and Handling.

 

Last February, in EID Journal: Post Mortem Stability Of The Ebola Virus, we saw a study that found that viable Ebola virus could be isolated 7 days post-mortem in cynomolgus macaques, and that viral RNA continued to be detectable reliably for 3 weeks and sporadically for up to 10 weeks. 

 

The authors wrote, `. . .  viable virus can persist for >7 days on surfaces of bodies, confirming that transmission from deceased persons is possible for an extended period after death.’

 

Today the same team of NIH researchers are back with another EID Dispatch, this time looking at the persistence of the Ebola virus in the environment.

Two of their most striking findings were;

1. That the Ebola virus lived longer on surfaces (stainless steel, plastic, or Tyvek) roughly twice as long in a climate controlled environment (temp 21°C, 40% RH) than it did in a  tropical environment (27°C, 80% relative humidity (RH)).
2. The Ebola virus remains viable in water for as long as 3 days at 27°C  or 6 days at 21°C

 

I’ve only excerpted part of the study, follow the link below to read it in its entirety.

 

Volume 21, Number 7—July 2015

Dispatch

Ebola Virus Stability on Surfaces and in Fluids in Simulated Outbreak Environments

Robert Fischer¹, Seth Judson¹, Kerri Miazgowicz, Trenton Bushmaker, Joseph Prescott, and Vincent J. Munster

Author affiliations: National Institutes of Health, Hamilton, Montana, USA

 

Abstract

We evaluated the stability of Ebola virus on surfaces and in fluids under simulated environmental conditions for the climate of West Africa and for climate-controlled hospitals. This virus remains viable for a longer duration on surfaces in hospital conditions than in African conditions and in liquid than in dried blood.

<SNIP>

We report stability of EBOV with a current outbreak strain from Guinea (Makona-WPGC07) (9) on 3 clinically relevant surfaces: stainless steel, plastic, and Tyvek (Dupont, Wilmington, DE, USA). We also determined the stability of EBOV in water, spiked human blood, and blood from infected nonhuman primates (NHPs). These experiments were conducted in 2 environmental conditions, 21°C, 40% RH, and 27°C, 80% RH, to simulate a climate-controlled hospital and the environment in West Africa, respectively.

Conclusions

We found that EBOV can persist on surfaces common in an ETU, highlighting the need for adherence to thorough disinfection and doffing protocols when exiting the ETUs and careful handling of medical waste. In addition, EBOV maintains viability for a longer duration in liquid than in dried blood. EBOV in blood of experimentally infected NHPs persists for a similar duration as EBOV in spiked human blood. A recent study showed that blood in the body cavity of an NHP contained viable EBOV for up to 7 days after death (13). We detected viable EBOV in drying blood for up to 5 days at both environmental conditions in human and NHP blood. Therefore, dried and liquid blood from an infected person in their home or ETU should be treated as potentially infectious. The finding that EBOV remains viable in water for as long as 3 (27°C) or 6 (21°C) days at the experimental concentration warrants further investigation into the persistence of the virus in aqueous environments, such as in wastewater or sewage canals. Viable EBOV has been isolated from urine (14) but not from human stool (8). Therefore, the potential for dissemination of EBOV through wastewater remains unknown.

This study is subject to several limitations. First, because standard volumes for samples were used, different volumes or matrices could influence the stability of EBOV under the tested conditions. Second, blood samples from the NHPs might have different immunologic or biochemical conditions, which can potentially influence virus stability. Third, the experimental conditions in the laboratory are sterile, but in disease-endemic areas and ETUs, bacteria or chemicals could influence EBOV viability.

Overall, we found that different environmental conditions, fluids, and surfaces influence the persistence of EBOV. These findings demonstrate that such factors are crucial in understanding transmission and improving safety practices.

Eurosurveillance: Environmental Stability Of MERS-CoV

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).

 

Stability of Middle East respiratory syndrome coronavirus (MERS-CoV) under different environmental conditions

N van Doremalen¹, T Bushmaker¹, V J Munster ()¹

1. Laboratory of Virology, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT, USA

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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

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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