Friday, 30 August 2013

A model of MERS-CoV acquisition (ver1)

With thanks to David Spalten (@dspalten) for discussion and considerations and AtRG for advice.

First we heard about Middle East respiratory syndrome coronavirus (MERS-CoV)-related viruses in bats in South Africa, then we read of antibodies in camels that reacted to MERS-CoV more than the most likely (known) other CoV to infect cattle, and most recently we were absorbed by the discovery of a probable parental strain of the MERS-CoV in the faeces of a Taphozous perforatus insectivorous bats.

We've also heard that most patients have not had direct or obvious contact with bats and we also know that pasteurised camel milk products should be safe. But that still leaves many stones unturned.

So if we can assume that the most likely route of acquisition of MERS-CoV is through the upper respiratory tract and that the spillover events come from animals (I'm including human-to-human exposures in this figure) then we need to consider how that might happen. I've included the animals above as well as baboons as they seem highly mobile, interact well with humans, visit mountains and caves (where bats are likely to hang out") and are found in the KSA. I've added ingestion but I don't really imagine how this could result in a respiratory infection, and MERS-CoV gastrointestinal involvement seems infrequent.

I don't live in the Kingdom of Saudi Arabia or in the Middle East and I do not profess to know much of the environment so what follows is "remote guestimation" at best. But I've thrown together some of the possible routes and animal players into a figure which may have some degree of reality buried in there somewhere. It may also spark an idea or two among those who do know what they're talking about.

So, here is my model of how humans may indirectly get a zoonotic infection from a primary or secondary animal host...
A model of MERS-CoV acquisition. Click to enlarge.
I'd be most happy to take suggestions for improvement of the figure. I know some of you like to use the graphics from the blog and Virology Down Under (which I strongly support, asking only for a specific reference to their source) so if they can be made more robust, I am very happy to do so. Get to me via the comment section below or on Twitter (see top right).