SARS, MERS and COVID-19—new threats; old lessons
Contrary to the widespread optimism of the mid-20th century, infectious diseases will never be relegated to history by antimicrobials and vaccines. ‘New’ human pathogens have emerged at intervals throughout human history but, until recently, emerging infectious diseases often remained unrecognized, and their causes unknown, long after they had become widespread. Now, scientists can often characterize emergent pathogens with astonishing speed, using next-generation sequencing and bioinformatics. In December 2019, in Wuhan, China, only a few days elapsed between collection of respiratory specimens from patients with viral pneumonia of unknown aetiology and the publication of the genome of the novel beta-coronavirus (now called SARS-CoV-2) that caused it.1 This led to rapid development of a diagnostic polymerase chain reaction (PCR) test and implementation of targeted containment measures. One might expect these technological advances, along with lessons from two previous novel coronavirus disease outbreaks—severe acute respiratory syndrome (SARS), in 2003 and Middle East respiratory syndrome (MERS), in 2012—to contribute to rapid control of the latest one, COVID-19. But, as Peeri et al.2 note in this issue, although there are similarities between SARS-CoV, MERS-CoV and SARS-CoV-2, there are key differences between the corresponding diseases, the global milieux into which they have emerged and international responses, that limit the relevance of lessons from previous outbreaks.