MERS is still lurking in the shadows

You may vaguely remember hearing of something called Middle East Respiratory Syndrome (MERS) a few years ago. You may even remember hearing that it’s transmitted to people by camels. Because that’s certainly a memorable reservoir for those of us living in areas without camels. And I wouldn’t be surprised if you thought that it had just sort of gone away because you haven’t heard anything about it in awhile.

I’m here to tell you, it hasn’t gone away.

History of MERS

MERS is a respiratory disease caused by a novel coronavirus (the same family of viruses that causes SARS) that was first identified in Saudi Arabia in 2012. Since 2012, 27 countries have reported cases of MERS. You can see from the figure below that most of the cases are located in the Middle East region. But even countries such as the US, UK and South Korea have reported cases. Saudi Arabia has reported most (over 80%) of the cases.

People get infected from other people or from camels. No one is totally sure how people get MERS from camels but they do know that to get it from another person you need to have very close contact. This is why much of the human-to-human transmission happens in healthcare settings and involves healthcare personnel getting infected too.

Since 2012 there have been 2 040 laboratory confirmed cases, although the number is probably higher as many mild cases are likely missed by surveillance efforts. Of those 2 040 cases, at least 712 have died (mortality rate of approximately 35%).

Global cases of MERS from 2012 to 2017. Most of the cases have been in Saudi Arabia.

Global cases of MERS from 2012 to 2017.

MERS today

You can see from the epi curve below that the number of MERS cases (around 100) first spiked in Saudi Arabia in 2014 and again in 2015. South Korea experienced a spike of about 90 cases in 2015 as well. Since then there have been smaller spikes in Saudi Arabia of around 30-40 cases. The most recent spike in Saudi Arabia happened just a few weeks ago. Cases continue to be reported between spikes. So we can safely assume that MERS and the camels that harbor MERS aren’t going anywhere anytime soon.

Epi curve of MERS cases reported to WHO as of 28 July 2017.

Epi curve of MERS cases reported to WHO as of 28 July 2017.

Since we’re not sure how people get MERS from camels we can’t totally prevent transmission. So what are we doing to prevent MERS? Researchers are trying to develop targeted therapies, that’s what.

Targeted MERS therapies

The best time for many researchers to develop treatments or vaccines is during these lulls between major outbreaks. Researchers who recently published a paper in Science Immunology were able to get blood samples from 21 (of the 2 040) people who’ve survived MERS. They’ve used these blood samples to learn more about MERS and how people respond to the infection.

What they learned is that the survivors who recovered the quickest didn’t have a super strong antibody response. Instead they had a strong killer T cell response. Therefore, many people may have had MERS but didn’t test positive because they didn’t make enough antibodies to trigger the laboratory test. So the mortality rate of MERS may be artificially inflated.

Those patients who developed the most severe cases of MERS actually had the strongest antibody response. The authors think this may have been because their T cells couldn’t clear the virus. Researchers are looking into ways to help patients by giving them short-term antibody infusions, similar to what was done with Ebola. It isn’t a cure but it could help those who are experiencing very serious illness.

There is still no vaccine for MERS. However, various researchers are working on developing one. At NIH’s Rocky Mountain Laboratory researchers are trying to train the immune systems of chimpanzees to target the protein the virus uses to invade cells. Another company, Invovio, is running clinical trials on a vaccine that uses the DNA of that specific viral protein to stimulate an immune response. But for any of these vaccines to have long-term effectiveness, they need to stimulate the antibodies as well as the T cells.

Let’s hope that researchers can remain one step ahead of MERS (and other coronaviruses) before it’s too late.

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