What is the difference between MERS and SARS?

Photo: Reuters

I recently visited South Korea on a business trip. I wasn't aware that they were having an outbreak of MERS until I went by one of their hospitals, and realised that several wards were closed. I remember when we had the SARS scare in our neck of the woods. How is MERS different from SARS?

There was a study published in the journal Lancet in 2013 about the differences between MERS and SARS. It was done while they were observing the MERS outbreak in the Middle East.

But first, let us recap. MERS stands for Middle East Respiratory Syndrome. SARS stands for Severe Acute Respiratory Syndrome. Both are caused by a coronavirus.

Did those two viruses originate from the same place?

No. SARS originated from Southern China in late 2002, and started spreading throughout the world in 2003. It affected more than 8,000 people and killed more than 900 patients.

No more SARS cases have been reported since 2003. Hopefully, the virus has died out.

MERS, on the other hand, is spreading. At the time of writing, in South Korea alone, there have been 175 cases with 27 deaths. Fourteen cases involve healthcare professionals.

Apparently, the South Korean virus is currently contained around healthcare facilities, and it hasn't entered the general public yet. Several hospitals have been closed to contain the virus.

MERS was initially reported in Saudi Arabia in 2012. It has spread to many countries since, including the US. Three to four out of every 10 patients have died.

SARS was believed to have originated from bats.

What type of patients do these different viruses target? The same? Or is there a difference?

For MERs, the patients seem to skew older, and are mostly male. The patients have a median age of 56 years old.

SARS, when it occurred in 2002-2003, was diagnosed in adults from 25 to 70 years of age. It did not seem to favour either male or female. It skewed primarily to younger patients who were healthy.

What about the way the diseases present? How is MERS different from SARS?

The incubation period between the two is quite similar. The incubation period is 5.2 days for MERS and 4.6 days for SARS.

But SARS spread very rapidly from person to person worldwide, thanks to a few "super" spreaders. In eight months, there were already more than 8,000 cases of SARS worldwide. The mortality rate in SARS was about 10 per cent.

MERS, in contrast, spread a lot more slowly. In 18 months after it was first detected in 2012, there were only 200 cases worldwide. Most of them were in the Arabian Peninsula. Sure, MERS has since spread to Europe, US, South Korea and even Hong Kong, but it has been a slower process over several years.

MERS, however, has a 40 per cent mortality rate. Nevertheless, experts question this because mild or asymptomatic infections may not have been recognised. If these cases were grouped together, the mortality rate might even be lower.

In MERS, 70 per cent of the deaths occurred in people with other diseases, according to a report published in 2014. These are diseases such as diabetes, kidney failure and heart disease.

However, another reviewer quickly pointed out that this observation is skewed because those initial patients who contracted MERS were all attending the same haemodialysis clinic in Saudi Arabia. Naturally, they would all have some sort of kidney disease, diabetes or even hypertension, leading to heart disease.

Apparently, MERS progresses to respiratory failure far quicker than SARS.

What about the symptoms in MERS compared to SARS?

If you have MERS, you typically develop a pneumonia-like illness. In short, you develop symptoms of high fever, cough and severe shortness of breath.

SARS also comes with a high fever, cough and severe shortness of breath.

In fact, these diseases are difficult to differentiate from severe bacterial infections.

These diseases are diagnosed as atypical pneumonia after the pneumonia that is caused by bacteria and viruses is ruled out. Of course, with an epidemic spreading, MERS is now the prime suspect if you develop such symptoms if you are in South Korea, or even if you have travelled to South Korea or the Middle East recently.

This is why airports in Malaysia and Singapore are now screening travellers who come from affected countries.

Dr YLM graduated as a medical doctor, and has been writing for many years on various subjects such as medicine, health, computers and entertainment. For further information, e-mail starhealth@thestar.com.my. The information contained in this column is for general educational purposes only. Neither The Star nor the author gives any warranty on accuracy, completeness, functionality, usefulness or other assurances as to such information. The Star and the author disclaim all responsibility for any losses, damage to property or personal injury suffered directly or indirectly from reliance on such information.