Scientists around the world are looking for the next SARS or MERS virus in wildlife from disease emergence ‘hotspots’.
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In late 2002, a new kind of lung infection began to emerge in the Guandong province of southern China. Patients came down with a fever, headaches and muscle pains, before developing a cough and difficulty breathing. As the disease began to spread further afield, images of people in surgical facemasks became a common sight on the news, and soon SARS (severe acute respiratory syndrome) developed into the first global pandemic of the 21st century. In total, the outbreak infected more than 8,000 people in 27 countries, leaving over 700 dead.
By July 2003, human-to-human transmission chains of SARS had been successfully broken, and the WHO announced that the pandemic was over. But scientists still didn’t know where the virus had come from. Initial theories focused on infected animals sold in Guandong’s markets. SARS was detected in ferret-badgers, raccoon dogs and mongoose-like creatures known as civets, which were slaughtered in their thousands when SARS returned to the country in 2004.
Large numbers of civets are farmed for food in China (they are used to make a delicacy called “dragon tiger phoenix soup”), but further research cast doubt on the idea that they were the original source of the disease. Although civets from animal markets tested positive for SARS, both farmed and wild populations of these animals were largely virus-free. This ruled them out as the natural reservoir for the virus, and implied that the overcrowded mixing of animals in the markets could have led to civets becoming infected by another, unknown host.
Researchers began searching local wildlife species for related pathogens that belonged to the same family as SARS – the coronaviruses. Primates, rodents and bats all seemed like possible suspects, and then, in 2005, two teams independently discovered SARS-like viruses in Chinese horseshoe bats. Their suspicions weren’t confirmed until 10 years after the initial outbreak, when a live coronavirus 99.9% similar to SARS was found inside a bat, confirming these flying mammals as the most likely origin of the deadly disease. Continue reading