Thursday, 17 November 2016

Another virus found to remain infectious on hard surfaces...

That headline doesn't bring in the readers. But - as far as we can tell having not been to the Nov 13-17 conference at which the preliminary data were presented during a seminar- it sums up the main finding of a new study on Zika virus (ZIKV).[1,2,4]

A 2016 Puerto Rico strain of the Asian lineage of ZIKV added to blood or a salt/protein solution was dried onto hard, solid surfaces. 

ZIKV was able to be recovered from those surfaces up to 8 hours later when in the presence of blood, but not the salty solution. 
Blood protected the virus. 

ZIKV recovery was achieved after rehydrating the dried material and adding dilutions to cells in culture (Vero E6 cells). There was no news on infectivity at warm temperatures or on cloth, tissues or other porous surfaces on which enveloped viruses like ZIKV usually don't do so well. By the way, when I say "recovered", I mean virus coudl be grown using lab conditions, producing more infectious virus. So the findings show that enough ZIKV remained infectious (or that it retained some infectivity) to start a new infection in lab cultures, despite being held outside the host cells it needs to replicate. 

Can ZIKV virus "live for hours" on surfaces? It's a virus - so it doesn't do much of anything outside of the living cell it completely depends upon for energy and raw materials ("dietary requirements"!). 

The main takeaway is not that the study defined a new route of ZIKV transmission to add to mosquitoes, sex, intrauterine transmission and transfusion.[11] This might have been your interpretation if you'd read...


.."The Zika virus is able to infect people even after sitting out on a counter for several hours, according to new research" [6]..

The study is really about the observations that some disinfecting agents (bleach and peracetic acid) may not work well when the virus is spilt onto these surface in the presence of blood. Isopropyl alcohol and quaternary ammonium/alcohol agents were still effective though.[3] West Nile virus (WNV) and bovine viral diarrhoea virus (BVDV) responded similarly. This is not a new finding for viruses in general, but it's a good one to have. This can be used as a reference for risk assessments for a lab that works with ZIKV or for healthcare facilities that may be dealing with ZIKV infected patients and needing to know how to effectively clean up spills or contaminated rooms.

Should we worry about this new finding?

Does the finding that a ZIKV spill can remain infectious on surfaces add new knowledge to our understanding of the risks of acquiring ZIKV infection? Not as far as we know because we have very limited evidence that ZIKV can infect a human through their epithelial surfaces (mucous membranes) - like we did have for Ebola virus for example. Such a route of infection - from surface to mucous membrane -is the the implied risk here. In other words, getting enough of those spilt infectious viruses into your eye, mouth or onto/into your nether regions. Its possible, but not likley and we have little evidence that its happens. 

We also have little evidence that ingesting something contaminated with infectious ZIKV or breathing it in can result in an infection. 

As ever, little evidence does not equate to zero evinced - we just have few actual data either because theses are such rare events or because we really haven't looked much (my bet).

Rare ZIKV transmission events do happen...

We have seen documented some unusual/infrequent ZIKV transmission events. Laboratory acquired infections [5,12] for example and that case of a severely immunocompromised/chronically ill adult passing ZIKV to his healthy adult son, perhaps via mucous membrane exposure to a high ZIKV load.[8,9] 

Infection of Dengue virus following exposure of a healthcare worker's mucous membranes to an infected IgM-positive patient's blood has also been described previously.[10] 

This route of transmission is certainly in need of some serious study. That said, transmission was not what this study was investigating. 

Infectious fluids such as blood, saliva, breast milk, urine or semen may come into contact with epithelial surfaces in a range of ways. 

Studies that do set out to focus on this interaction and measure how often an infection results from this contact, are needed. 


References...

  1. Research finds Zika virus can live for hours on hard, non-porous surfaces
    https://www.eurekalert.org/pub_releases/2016-11/aaop-rfz111116.php
  2. Zika virus can survive on hard surfaces for hours, researchers say
    http://www.upi.com/Health_News/2016/11/15/Zika-virus-can-survive-on-hard-surfaces-for-hours-researchers-say/9781479267969/
  3. Study: Zika virus can linger on hard surfaces
    http://www.cidrap.umn.edu/news-perspective/2016/11/study-zika-virus-can-linger-hard-surfaces
  4. Inactivation of Zika Virus on a Hard Non-porous Surface
    https://annual.aapsmeeting.org/event/member/309446
  5. http://www.achd.net/pr/pubs/2016release/060916_zika.html
  6. Zika can survive for hours on hard, nonporous surfaces
    http://www.cnbc.com/2016/11/15/zika-can-survive-for-hours-on-hard-nonporous-surfaces.html
  7. Zika virus can live for hours on hard, non-porous surfaces
    https://www.sciencedaily.com/releases/2016/11/161115164220.htm
  8. Scientists just documented the first case of Zika spreading through physical contact
    http://www.sciencealert.com/scientists-just-documented-the-first-case-of-zika-spreading-through-physical-contact
  9. Fatal Zika Virus Infection with Secondary Nonsexual Transmission
    http://www.nejm.org/doi/full/10.1056/NEJMc1610613?query=featured_home&
  10. Transmission of Dengue Virus without a Mosquito Vector: Nosocomial Mucocutaneous Transmission and Other Routes of Transmission
    http://cid.oxfordjournals.org/content/39/6/e56
  11. Zika Virus Disease Cases - 50 States and the District of Columbia, January 1-July 31, 2016.
    https://www.ncbi.nlm.nih.gov/pubmed/27631604
  12. http://www.cdc.gov/zika/transmission/