Coronaviruses are a large family of viruses that typically affect the respiratory tracts of birds and mammals, including humans. Human coronaviruses (CoV) can cause a variety of illnesses ranging from the common cold to more severe diseases such as the Middle East respiratory syndrome and Severe Acute respiratory syndrome, more commonly known as MERS-CoV and SARS-CoV.
Human coronaviruses vary greatly in severity and risk. The four non-severe strains of Human coronavirus (229E, NL63, OC43 and HKU1) generally produce mild symptoms akin to the common cold. However, they can also cause colds with major symptoms, such as fever and sore throat. The other three strains (MERS-CoV, SARS-CoV, SARS-CoV-2) are potentially more severe, and can cause major respiratory illnesses such as pneumonia and bronchitis.
In 2019, a new deadly coronavirus outbreak was identified in China and quickly spread to other countries. Coronavirus disease 2019, or COVID-19 is caused by the virus SARS-CoV-2, or Severe Acute Respiratory syndrome coronavirus. The origin of SARS-CoV-2 is believed to have an animal origin through spill over, but the quick spread of infection is almost entirely from human-to-human transmission. As of record, the earliest known infection occurred on 17 November 2019 in Wuhan, China.
[Severe Acute respiratory syndrome]
SARS is a severe strain of coronavirus that quickly spread around the world in early 2003. During the outbreak, which originated in China and spread to 26 countries in North America, South America, Europe, and Asia, approximately 8,000 people were infected and the mortality rate was 9%. However, this rate was much higher with people over the age of 60. Scientists trace the origins of SARS to bat-infected civet cats most likely sold at a wild animal market in China, but the majority of the transmission was human-to-human. Overall, nearly 800 people died. As of 2004 the SARS virus seemed to have been contained.
[Middle East respiratory syndrome-related coronavirus]
MERS or also known as the camel flu, is another severe strain of coronavirus that originated in Saudi Arabia in 2012. This more recent outbreak was also deadly as it produced severe flu-like symptoms including fever, cough, diarrhea and shortness of breath and had a mortality rate of 33% of infected patients. Similarly to the SARS strain of coronavirus, the origins of MERS are also zoonotic most likely from infected bats transmitting the disease to camels. Since 2012, there have been 2,494 confirmed cases of MERS in 27 countries and 858 people have died from the disease.
[Corona disease 2019 or COVID-19]
COVID-19 is an infectious respiratory illness caused by the coronavirus SARS-CoV-2. Symptoms can be mild and include fever, dry cough, and shortness of breath, but can also be severe progressing to pneumonia and multi-organ failure. Authorities first discovered the virus in Wuhan, China at the end of December 2019. From the onset it was believed that this virus was zoonotic, originating from an animal and seafood market, but the recent rate of infection confirms that humans can pass the virus to each other without prior contact to infected animals.
Since late 2019, the virus has spread rapidly to other countries, both in and outside of Asia, leading the World Health Organization (WHO) to declare this a pandemic. As of 24 March 2019, more than 375,000 people have contracted the virus, and over 16,000 people have died from it worldwide.