Shingles infectivity

After having a case of shingles and two more suspected cases (which turned out not to be) at the care home where I work, I thought it might be useful to put together a protocol for staff. I posted this to the forum to check I hadn’t made any egregious errors, and the question was raised of whether I was giving them the correct advice on infectivity. I’d assumed it was the same as for chicken pox, but in fact, although the same virus is involved, a person with shingles is rather less likely to pass it on. But how likely, and what precautions do we need to take? This turned out to be more complicated than I’d anticipated.

Firstly, there seems to be no doubt that being in contact with the rash is a risk, as you might expect. The virus can also persist on bed linen, towels, and washcloths. This has obvious implications for staff, and one of the issues I had to consider was whether to request that all staff be asked to have routine varicella testing as part of employment. That way, we would know which staff could safely work with residents that have shingles.

The question, however, is what risk is involved in being in the same room as someone with shingles whose rash is covered. In other words, is droplet transmission a factor?

Accepted wisdom says no (unless the person with shingles is immunosuppressed). However, when I raised the question on DNUK, one helpful person found me some links, including this useful summary of evidence on Medscape. One particularly notable case history cited by that article was of a healthy, immunocompetent patient in hospital with shingles; PCR on swabs taken from various places in the room, including an air filter which the patient hadn’t touched, confirmed that she was, in fact, breathing out VZV. But how much? That study can’t give us quantitative accounts.

The article also cited some interesting-sounding Russian studies; one that quantified the amount of virus spread by patients with shingles as being a quarter of that spread by patients with chicken pox, one that confirmed cases of chicken pox occuring as spread from shingles, and, most annoyingly tantalising of all, one that had apparently followed over two thousand patients over a ten-year period, figured out the degree to which droplet spread and chicken pox infection were an issue, and, from this, come up with what sounded like exactly the sort of detailed instructions I was looking for, available to anyone who could not only get hold of the article in question but who could read Russian. So, that’s helpful, then.

The only thing I could find on Public Health England was a guideline for inmates in prison or other places of detention; this advised that viral spread from shingles can occur ‘if the lesion is on an exposed site and there is direct contact with a susceptible person’ and that a significant contact would be ‘direct contact with a shingles rash on an exposed part of the body when the lesions have not yet crusted over’ which would seem to imply that droplet spread isn’t an issue. However, the guideline then goes on to advise isolation for affected detainees without differentiating between chicken pox and shingles, so that’s a little unclear.

The CDC guidelines advise avoiding people in specific high-risk categories; namely, pregnant women, premature or LBW babies, and the immunosuppressed. The implication there, although not stated, seems to be that you don’t have to avoid people in other categories as long as the rash is covered.

I think the bottom line is that no-one knows for sure. (Apart from some people in Russia.) So, it is in effect a matter of balancing a theoretical low risk of infection against the known harm to a care home resident of having to stay in isolation when they want to be out and doing things (plus, I might add, the difficulty of enforcing this in the case of some of our demented patients). My inclination, after reading all this, was not to order isolation for shingles patients.

I contacted the local microbiology team, from where the consultant advised me that this was correct as long as the rash could be covered, but that patients with an uncovered rash should be isolated. This seems a fair compromise. She also agreed that it would be advisable for all care home staff to have their immunity to varicella checked, but advised that this needed to be the decision of the home’s occupational health department and that I should contact them.

Armed with that information, I shall complete the protocol and send it to the care home, and I’ve raised the issue of immunity testing with the care home manager as something to pass on to their OH department; she agreed this was a good idea.



About Dr Sarah

I'm a GP with a husband and two young children.
This entry was posted in Credits 2017, DENs, Infectious Diseases. Bookmark the permalink.

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