It's been one year since reports first emerged that a viral "pneumonia of unknown cause" infecting dozens in China had been identified as a novel coronavirus.
That novel coronavirus, SARS-CoV-2, is now known to cause COVID-19, an illness that has wreaked havoc on the planet, upended normal life, and killed more than 1.8 million people globally.
There have been more than 87 million infections throughout the world and as the virus spread in April, more than half of humanity was in lockdown or restricted.
Chinese state television first reported that the mystery illness was likely a novel coronavirus on January 9, 2020, the same day the World Health Organization (WHO) says they reported the information.
It is the seventh known coronavirus to infect humans with many of these viruses causing upper respiratory illness or the common cold.
The other two coronaviruses that cause severe illness are SARS (Severe acute respiratory syndrome) and MERS (Middle East respiratory syndrome), which both caused outbreaks but did not spread as widely or as rapidly as COVID-19.
In the SARS outbreak from 2002 to 2003, nearly 8,100 people were infected and 774 died. There have been 2,519 cases of MERS reported since 2012 and 866 deaths.
Coronaviruses are named for a protruding spike protein which looks like a crown. Corona means crown in Latin.
That protein also facilitates the virus' entry into cells. It is what the approved vaccines developed to help end the pandemic are targeting.
Like SARS and MERS, COVID-19 likely originated from an animal source.
What happened after it was determined there was a novel coronavirus in China?
In the days that followed the discovery of the novel coronavirus, the WHO put out guidelines on how to test for the virus and prevent infection.
Early guidance for healthcare workers suggested wearing a medical mask, gloves and a gown to prevent infection. It also warned of some risk of aerosol transmission while performing some ventilation procedures.
The month that followed in January 2020 was marked by fast developments in the pandemic, with the virus' genome sequence shared globally days after reports of the coronavirus.
By the end of the month, the WHO would declare the novel coronavirus a global health emergency with cases already identified in Asia, Europe and the US.