When a deadly disease emerged in South China's Guangdong province in late 2002, and patients began to die, there was no definite diagnosis as to the cause of death. An epidemic quickly spread nationwide and then to other countries and regions.
It wasn't until five months later, after 774 deaths in 37 countries, that scientists in Canada identified the SARS virus as the source of the infection.
To prevent such a tragedy from happening again, scientists began looking into unknown viruses.
Now an international team led by Chinese virologists has reported, in an article scheduled to be published by Nature magazine on Thursday, the discovery of 1,445 new virus species.
"In the past, we have discovered new viruses only after an outbreak. Some viruses have even remained unknown for decades," Zhang Yongzhen, a researcher at the National Institute for Communicable Disease Control and Prevention, said on Wednesday.
The institute is part of the Chinese Center for Disease Control and Prevention.
"With the lesson learned from SARS, we started to wonder how many unknown diseases are waiting for us. And that is the starting point of this research - to learn of viruses before an epidemic happens," said Zhang.
Starting in 2011, the scientists studied more than 220 invertebrate species - a wide range of creatures such as insects that account for 95 percent of the world's animals - and found the new viruses.
"The discovery of a new virus was slow in the past because most scientists were concentrating on vertebrates such as birds, pigs and dogs, since it was natural for people to inspect livestock first when an epidemic emerged," Zhang said.
"Based on our study, invertebrates, which are much greater in number, carry far more viruses than we were aware of. Also, many vertebrate viruses may have originated from invertebrates."
The International Committee on Taxonomy of Viruses began to devise and implement rules for the naming and classification of viruses early in the 1970s, an effort that continues today. In the latest classification, published in 2011, only 2,284 species of viruses were defined.
"The enormous diversity of lineages and genome structures they describe (in the article) undoubtedly revolutionize our understanding of the virosphere," said one peer review provided to Nature that was shared with China Daily.