COVID-19 is a zoonotic illness caused by one of many hundreds of coronaviruses. Other notable coronaviruses are MERS 2012 and SARS 2003. A zoonotic virus causes disease in animals, but has made the jump to humans. When humans encroach on territory held by wild animals, the risk of humans coming into contact with novel zoonotic diseases is heightened. The close proximity of live animals and animal slaughter practices increase this risk, and this was the case in the wet market in Wuhan where the outbreak has been traced back to. Although there is still not sufficient evidence to indicate exactly how this specific coronavirus was transferred to human beings, there have been some attempts to understand exactly what happened, which you can read here.
The animal origin of COVID-19 has not yet been identified, but bats are a possible source. Bats are hosts to many types of zoonotic viruses, including Ebola, HIV and rabies. Zoonotic diseases usually stay locked away in nature, but are often unearthed because of human behaviour. This is why there have been calls to ban wildlife markets in response to the COVID-19 outbreak. Research suggests that COVID-19 could be a chimera between two types of pre-existing viruses, but we still cannot say from which animal species.
As with any issue of global concern, alternative theories circulate. Read some of the most common debunked conspiracies on COVID-19 here.
In 80% of people, COVID-19 is a mild illness and causes symptoms similar to cold and flu. Recently, the loss of smell and taste have emerged as common COVID-19 symptoms. The virus spreads through droplets when a person coughs, sneezes or exhales. There are currently no curative treatments for COVID-19, and the management of very unwell individuals is supportive.