Camels at the centre, aerosol all around...

v2 12JUN2015

A droplet (and perhaps airborne)-centric view of how the camel could be a source of sporadic human infection by MERS-CoV, a virus that is genetically very similar whether found in camels or humans.

The inner ring (orange) is more about bigger wetter droplets and aerosols-if you must differentiate on size. 

These are potential routes by which a human in contact with, or near to, camels might acquire virus from them, when those camels are actively infected. Keep this in context though- because of a number of large hospital-based outbreaks, most cases of MERS seem to have occurred by virus transmission between humans and their environments rather than from camels to humans.

Camels are not all infected all the time. This is probably why there wasn't a rash of camel herdsmen coming down with MERS after the YouTube camel-kissing outbreak...at least as far as we know there wasn't.

Camels have been found to be actively infected more often when young, but adult camels have also been found actively infected by MERS-CoV as well so there is risk of exposure to camels at any age, when they are infected.

Sometimes camels do not show signs of illness (e.g. no runny nose) but other times they do, so illness alone cannot be used as a warning sign.

There are also some data to suggest adult camels can be reinfected. This makes sense if you remember that MERS-CoV is well entrenched among camels spread over large areas of the Arabian Peninsula and Africa. The virus would disappear if there were no susceptible hosts left among the adults to maintain it in the herds between camel breeding seasons. Plus, there is nothing to physically stop a new infection anyway. That's a conversation about whether that infection leads to notable or debilitating disease or not.

The outer (Blue) ring in the picture above is more about consumption of camel products. As you can see in the inner ring, some of these activities could also generate aerosols and it is important to think about, and recognize, that avoiding consuming of camel products may still be about reducing your risk of exposure to virus that you can breathe in during the process of preparing the camel products to consume, when the camel is infected.

We don't yet have any evidence that the virus can infect after eating/drinking material contaminated with it. Or whether many camel products are contaminated with it. I tend to think that if eating/drinking were a route to acquiring MERS, then a lot more people would be infected by such a deliberate process of viral delivery. Plus. the disease almost always shows up as a respiratory tract illness with gut issues thrown in sometimes, not the other way around. And the physiology underpinning a virus being ingested, disseminating systemically and mostly showing up as pneumonia? Plus the few exported cases that have forward transmitted probably weren't consuming camel products at their destinations. Meh. Droplets. Respiratory

So we still need to find out which bits of the camel actually have virus in them. No milk testing has been done yet but nasal swabs and faeces have been positive for MERS-CoV RNA and have had infectious virus grown from them.

On cleaning this blight from the camels, I'd like to see more talk about quarantine and isolation processes now. Can camel herds be kept separated for long enough that the virus is "burned out" of each herd by limiting its ability to infect new herds? It would be a huge job but it may be a way to rid areas, countries and perhaps the Peninsula of MERS-CoV while routine animal testing can be put in place for imported camels. Just a thought. In the meantime, finding ways to perhaps do this on a small scale for the incoming pilgrims so that they could still visit with "safe" camels, might be a matter of priority.

Make no mistake, camels host this virus and they have done so for at least 20-years.

That's not the end of the story - but it's one chapter of it and it's written in stone.


Version history.

• v2-changed some use of the term 'airborne' as my understanding of the word has mutated over the past year

MERS and camels....urine drinking seems to be a very wide ranging thing...

A video of camel urine being collected by a band of merry (although somewhat coughy) men.

http://www.youtube.com/watch?v=fFk0rXkv0xc&feature=youtube_gdata_player

While the intended uses for camel urine extend from prolonging life to treating cancer to preventing hair loss (none of which have been proven effective in clinical studies as I understand it), consumption among tribes and others in the Kingdom of Saudi Arabia seems to be much more widespread than I, in my ignorance, had thought.

It still remains unclear whether MERS-CoV is actually shed in the urine from infected camels. This is strange to me given that there have now been quite a few camel studies, including those that used PCR-based (real-time reverse transcription PCR that is) methods quite capable of detecting infectious virus. There also seems to be plenty of opportunities to sample already collected urine by PCR. The camel testing focus has been mostly on respiratory secretions and faeces; urine gets missed off the list of samples to be tested. Why? I don't know. Hopefully that will change soon as the science catches up to the realities of lifestyle, however widespread or niche, that those practices may be.

What also really frustrates me is that because camel urine is consumed by drinking, the next step for many is that MERS-CoV must be infecting through the oral route. That does not necessarily track. Urination, defecation, coughing, sneezing, flushing a toilet, talking even breathing can create aerosols that can be inhaled. An aerosol being tiny droplets or floating "nuclei" (dried down droplet that remains airborne for much longer than the larger hydrated form). 

To me at least, this would seem to be to be a much more logical and probable way of acquiring the respiratory disease that is MERS on presentation. At least much more probable that swallowing and needing to inhale some of that into the airways. They may not be exclusive events; swallowing may create aerosols too, but I'm thinking more in terms of the most likely or frequent methods for acquiring a respiratory infection, which is what MERS seems to start off being. 

Keeping in mind that animal studies of hamsters have shown that drinking can result in airway infection by virus - but do we drink like a hamster in a cage? I don't know that we do and I remain very dubious of the relevance of those sorts of findings in humans.

Just some thoughts anyway.

Many thanks to all on Twitter who continue to educate me on camel-related practices in far-off lands. Pleas note that I do not intend to belittle any practice and I sincerely hope it doesn't come across that way. I'm seeking only to try and understand how MERS-CoV may spread, and by extrapolation, how other viruses may spread among animals and to people in the future. 

Spillover events like MERS-CoV infections and H5N1 and H7N9 and H10N8....are going to keep happening but hopefully the knowledge we acquire from each outbreak can speed up our efforts to track the source for the next one. Whatever that source may be. Ultimately, such work needs to be done by the country harbouring the infection though because, resource permitting, they can do it most quickly; so this sort of education is secondary to putting in place the infrastructure and people to accept that education.