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SARS, MERS …? Preparing for the next coronavirus pandemic

The 2003 SARS outbreak spread from southern China to most parts of the world, resulting in more than 8,000 human infections and almost 800 deaths. KARL GOH/EPA

The outbreak of severe acute respiratory syndrome (SARS) was one of the more serious recent pandemics. It was caused by a member of the coronavirus family, and now another such virus is causing illness in the Middle East.

In 2003, SARS spread from southern China to most parts of the world, resulting in more than 8,000 human infections and almost 800 deaths. It caused great panic in the international community for two reasons – nobody knew what it was or where it came from.

And it disappeared as inexplicably as it had appeared. After SARS was gone, the key question was whether it would come back. This was answered last year when a new SARS-like virus emerged in the Middle East

Enter MERS

This virus, known as Middle East Respiratory Syndrome (MERS), has caused an ongoing outbreak of respiratory disease. As a result of the ease of modern travel, MERS has spread from Saudi Arabia, Jordan, Qatar and the United Arab Emirates to the United Kingdom, Germany, France, Italy and Tunisia.

MERS appears to be even deadlier than SARS as it has more than a 30% mortality rate; so far, it has killed 45 of the 82 people diagnosed with it.

Although the World Health Organization (WHO) hasn’t classed MERS as an emergency or pandemic, the international health community is poised for whatever comes next. A subtle change in the virus, making it more contagious or virulent, could drastically change the situation.

There are key similarities between this and the 2002-03 SARS outbreak, and we need to learn from our past to help us prepare for current and future biosecurity threats.

An artificially coloured electron micrograph of the Middle East Respiratory Syndrome (MERS). CSIRO

Prior to the emergence of SARS, coronaviruses had been detected in both human and livestock populations. But all previously known human coronaviruses only caused mild respiratory symptoms and had never been associated with severe human disease.

This is what made SARS unique. And it complicated the search for the specific cause of the illness (cornonaviruses had not been extensively researched before) and its origin even more complex.

Initial evidence suggested that the SARS coronavirus was likely an animal virus that had crossed the species barrier into the human population. But working out the animal that was its natural host proved challenging.

At the time (2005), we (the current authors) led an international team that identified that bats were the likely reservoir host of a SARS-like coronavirus. But we still haven’t found the animal host of the exact SARS virus.

Virus reservoirs

Since the mid-1990s, bats have been recognised as an important source of many emerging viruses that can cause severe or lethal disease in people and livestock. These include the Hendra, Nipah, Ebola, Marburg, Menangle and Melaka viruses.

Our discovery of the SARS-like bat coronavirus in 2005 triggered a surge of international interest in bat coronaviruses. Genetic evidence of more than 100 different coronaviruses were discovered in bats across all continents.

Based on the bat coronavirus data obtained by our group and others around the world, we feared there was a high chance that the SARS coronavirus or one related to it could re-emerge.

What we could not predict was when or where it would happen. But this was addressed by the MERS outbreak. We know that there are other related viruses that could also spill out of their bat hosts and infect people.

Chinese horseshoe bats harbour coronaviruses closely related to the SARS virus. Zhang Libiao/Guangdong Entomological Institute

Preparing for new viruses

While we are unable to prevent future coronavirus spillovers, there are a number of things we can do to lessen the risk of it happening.

Once we identify the host species and the conditions for spillover, we can try to limit the opportunity for human infection. Restrictions on the interactions between wild bats and other species at markets, for instance, has so far prevented the re-emergence of SARS in China or any other part of the world.

We can also enhance early detection and rapid response capacities to combat outbreaks through international collaborations with more systematic surveillance, sharing of diagnostic and research tools, and rapid exchange of key scientific information.

Controlling emerging diseases, such as SARS and MERS, takes not only a global effort but a multi-disciplinary one. Our response to the next human pandemic threat needs to combine medical, veterinary, ecological and environmental expertise to tackle the disease threat at the source.

Such approaches will help protect the global community from the next pandemic.

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