Monday, June 29, 2020

mSphere: Environmental Contamination From Asymptomatic COVID-19 Patients & Nature: Face Touching Study


Yesterday, in EID Journal: Prolonged Infectivity of SARS-CoV-2 in Fomites, we looked at the viability of our pandemic coronavirus on inanimate objects, whose infectivity was remarkably preserved in the presence of proteins, such as those found in human respiratory fluids.

Today, we have two related reports

Briefly, the first - published today in the journal Nature - looks at the frequency of our unconscious touching of our hair, face, neck, and shoulders (HFNS).

In yesterday's blog, I mentioned an older study (see AJIC Face touching: A frequent habit that has implications for hand hygiene) which showed that when in public, we touch our face/mouth/nose frequently; often 20+ times an hour.
This first study, based on the analysis of over 75 hours of video surveillance at a Chinese graduate student office, found - among other things - that the subjects spent a remarkable 9% of their time touching their own hair, face, neck, and shoulders (HFNS).

It's a fascinating report, and while limited to a 5-day observation period and to a cohort who knew they were being observed (see APIC: The Impact Of The Hawthorne Effect On Hand Hygiene Audits), it provides a wealth of behavioral information with infection control implications.

Follow the link to read the study in its entirety. 

Nan Zhang, Wei Jia, Peihua Wang, Marco-Felipe King, Pak-To Chan & Yuguo Li 

Scientific Reports volume 10, Article number: 10457 (2020) Cite this article
Self-touch may promote the transfer of microorganisms between body parts or surfaces to mucosa. In overt videography of a post-graduate office, students spent 9% of their time touching their own hair, face, neck, and shoulders (HFNS). These data were collected from 274,000 s of surveillance video in a Chinese graduate student office. The non-dominant hand contributed to 66.1% of HFNS-touches.
Most importantly, mucous membranes were touched, on average, 34.3 (SE = 2.4) times per hour, which the non-dominant hand contributed to 240% more than the dominant hand.
Gender had no significant effect on touch frequency, but a significant effect on duration per touch. The duration per touch on the HFNS was fitted with a log–log linear distribution. Touch behaviour analysis included surface combinations and a probability matrix for sequential touches of 20 sub-surfaces. These findings may partly explain the observed variation in the literature regarding the microbiome community distribution on human skin, supporting the importance of indirect contact transmission route in some respiratory disease transmission and providing data for risk analysis of infection spread and control. 
From our study, washing the nondominant hand is more important because of the higher frequency of touching the mucous membranes. In addition, not only the airborne and large droplet routes, but also the fomite route, can be effectively reduced by wearing surgical masks. The eyes, nostrils and lips are three mucous membranes on the face. Only 6.6% of touches of the mucous membranes were on the eyes, which means 93.4% of viral transfer could be blocked by wearing a surgical mask.
(Continue . . . )
Today's second study, published this past week in mSphere, looks at the environmental contamination due to the shedding of SARS-CoV-2 from asymptomatic and mild cases in a non-ICU negative-pressure isolation ward in China. 

If this sounds vaguely familiar, roughly six weeks ago, in EID Journal: Detection of SARS-CoV-2 on Surfaces in Quarantine Rooms, we looked at the extensive contamination of a hotel room occupied overnight by two presymptomatic COVID-19 cases, also in China. 

First the link and abstract to this study (which you'll want to read in its entirety), then I'll return with a postscript. 

Li Wei, Ji Lin, Xiaofei Duan, Wenzhi Huang, Xiaojun Lu, Juan Zhou, Zhiyong Zong
Katherine McMahon, Editor

DOI: 10.1128/mSphere.00442-20


The contamination of patients’ surroundings by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) remains understudied. We sampled the surroundings and the air of six negative-pressure non-intensive care unit (non-ICU) rooms in a designated isolation ward in Chengdu, China, that were occupied by 13 laboratory-confirmed coronavirus disease 2019 (COVID-19) patients who had returned from overseas travel, including 2 asymptomatic patients.

A total of 44 of 112 (39.3%) surface samples were positive for SARS-CoV-2 as detected by real-time PCR, suggesting extensive contamination, although all of the air samples were negative.

In particular, in a single room occupied by an asymptomatic patient, four sites were SARS-CoV-2 positive, highlighting that asymptomatic COVID-19 patients do contaminate their surroundings and impose risks for others with close contact. Placement of COVID-19 patients in rooms with negative pressure may bring a false feeling of safety, and the importance of rigorous environment cleaning should be emphasized.

IMPORTANCE Although it has been well recognized that the virus SARS-CoV-2, the causative agent of COVID-19, can be acquired by exposure to fomites, surprisingly, the contamination of patients’ surroundings by SARS-CoV-2 is largely unknown, as there have been few studies. We performed an environmental sampling study for 13 laboratory-confirmed COVID-19 patients and found extensive contamination of patients’ surroundings.
In particular, we found that asymptomatic COVID-19 patients contaminated their surroundings and therefore imposed risks for other people. Environment cleaning should be emphasized in negative-pressure rooms. The findings may be useful to guide infection control practice to protect health care workers
(Continue . . . )

While it seems probable that symptomatic COVID-19 cases shed far more virus and are better able contaminate their surroundings than asymptomatic or presymptomatic carriers, they are also more more easily identified and avoided than `stealth' carriers of SARS-CoV-2. 

How much of an impact that asymptomatic shedding of the virus has on the spread of COVID-19 has yet to be quantified, but the evidence for its contribution continues to mount.

EID Journal: Persistence of SARS-CoV-2 in Aerosol Suspensions

EID Journal: Asymptomatic or Presymptomatic Transmission Of SARS-CoV-2

MMWR: Asymptomatic & Presymptomatic SARS-CoV-2 Infections in Residents of a LTCF

Presymptomatic Transmission of SARS-CoV-2 — Singapore, January 23–March 16, 2020

Transmission of 2019-nCoV Infection from an Asymptomatic Contact in Germany

When you combine the shedding studies (of both symptomatic & asymptomatic) cases with the fomite contamination and environmental persistence studies, it isn't hard to understand why cases are suddenly surging in Florida, Texas, California and many other states where social distancing rules have recently been relaxed. 

While stealth transmission is undeniably harder to protect against, it can be done.  

Social distancing, scrupulous hand hygiene, wearing face covers, and avoiding touching your face are all things that can reduce the risk of picking up the virus from individuals, the air, or from contaminated surfaces. 

Granted, following this advice rigorously isn't easy, particularly in the summer. Masks and face covers are hot and uncomfortable, and after months of social isolation people want to mingle and have fun.
But we are currently seeing what comes from a month of not doing these things in a pandemic.
In Florida, that has meant more than a 10-fold increase in daily cases in the past 30 days (see chart below), which corresponds to the relaxation of social distancing rules starting on Memorial Day weekend. 

Florida COVID-19 Dashboard June 29th
While going back to a `lockdown' is both socially and economically unacceptable, we need to do a much better job of preventing COVID-19 transmission, even if it is inconvenient.  

Because if we allow these trends continue for very much longer, hospitals will start to become overwhelmed, deaths will inexorably rise, and any hopes for a quick economic recovery will vanish.
Making the future course of this pandemic literally in - and arguably on - our hands.