I was part of the panel for the latest HIS webinar earlier this week. And here it is:Continue reading
We know that respiratory viruses can be spread through droplets, occasionally aerosols, and contact routes (see Figure 1). But what is the relative importance of these transmission routes for the SARS-CoV-2 virus, which causes COVID-19? A new pre-print paper published yesterday provides evidence that the stability of the SARS-CoV-2 coronavirus is broadly comparable to the ‘original’ SARS coronavirus (SARS-CoV-1) on dry surfaces and in aerosols. This paper supports an important role for dry surface contamination and aerosols in the spread of SARS-CoV-2, and suggests that improved environmental persistence isn’t the key to the relative success of SARS-CoV-2 over SARS-CoV-1.
Figure 1: Transmission routes of respiratory viruses (from this review article).
This recent study from the Donskey group could provide hospital cleaning staff with a powerful visual cue to help assure adequate disinfectant coverage. The addition of a chemical widget to bleach solution gives it a bright blue hue when applied to surfaces, so allowing a cleaner to track their progress visually!
Thought I’d share some key points from the 2016 HIS Spring Meeting.
Outlining the problem(s)
Prof Gary French kicked off the meeting with a (sic) historical perspective, describing how the perceived importance of the environment in transmission has oscillated from important (in the 40s and 40s) to unimportant in the 70s and 80s to important again in the 2000s. Gary cited a report from the American Hospital Association Committee on Infections Within Hospitals from 1974 to prove the point: ‘The occurrence of nosocomial infection has not been related to levels of microbial contamination of air, surfaces and fomites … meaningful standards for permissible levels of such contamination do not exist.’ Gary covered compelling data that contaminated environmental surfaces make an important contribution to the transmission of Gram-positive bacteria and spores, highlighting that C. difficile in particular is a tricky customer, not helped by the fact that many ‘sporicides’ are not sporicidal!
Most virologists would probably tell you that enveloped viruses are generally pretty fragile outside of their host and so wouldn’t survive for long on dry surfaces. They may well say “If you were talking about a non-enveloped virus (like norovirus) then, yes, it would probably survive on surfaces for quite a while. But enveloped viruses, no – you’d be lucky if it survived for more than a few hours.” But when I looked at the literature to investigate the potential for dry surface-mediated transmission of respiratory viruses with pandemic potential (SARS, MERS and influenza), the picture that emerged was quite different. These respiratory viruses can survive on dry surfaces for ages, and the contaminated environment may well be an underestimated reservoir for their transmission. This is summarised in a review published recently in the Journal of Hospital Infection.