What is a Human Coronavirus?
Coronaviruses are single-stranded RNA viruses commonly seen in birds, bats, livestock, and occasionally humans. They are zoonotic in origin, meaning that they are initially transmitted to humans through animals. Most human coronavirus infections are caused by the 229E, NL63, OC43, and HKU1 strains, which have been diagnosed in humans since the 1960s. Similar to the common cold, there is currently no cure for coronavirus, and contracting one form of the virus will not grant immunity from other strains.
A Brief History of Human Coronaviruses
A more severe form of human coronavirus, the SARS-associated coronavirus, or SARS-CoV, appeared in China in 2002, causing a global outbreak in early 2003. SARS-CoV is named for the pneumonia-like condition it causes, Severe Acute Respiratory Syndrome, which can be fatal in humans. Over the course of the 2003 outbreak, over 8000 people contracted SARS-CoV and 774 deaths were reported. No human cases of SARS-CoV have been reported since 2004.
Another form of human coronavirus, the Middle East Respiratory Syndrome Coronavirus, or MERS-CoV, first appeared in Jordan in 2012. Most cases of MERS-CoV occur in countries located on the Arabian Peninsula, with outbreaks in other countries being linked to travel from infected areas. MERS-CoV can cause severe symptoms including fever, pneumonia, and kidney failure, and like SARS-CoV can be fatal. The virus is believed to have been transmitted from bats to camels and then finally to humans. In 2014, the only two known cases of MERS-CoV in the United States were diagnosed in people who had recently traveled to Saudi Arabia; both patients recovered, and the disease has not appeared in the United States since.
Human coronavirus (Dr. Fred Murphy & Sylvia Whitfield/CDC)
Recently, a new strain of human coronavirus has appeared in Wuhan, China. The virus was initially named novel coronavirus 2019, but more recently has been simply referred to as 2019-nCoV, or severe acute respiratory syndrome coronavirus 2 ( SARS-CoV-2).
Over 37,000 cases of 2019-nCoV and over 800 deaths have been reported worldwide, exceeding the death total of the 2003 SARS outbreak, which saw 774 deaths out of over 8,000 cases. The percent of deaths to reported cases for 2019-nCoV is currently calculated at just over 2%, as compared to a roughly 10% fatality rate for SARS and over 30% fatality rate for MERS. (Keep in mind this is not a definitive fatality rate for 2019-nCoV, and is not proof that 2019-nCoV is less or more dangerous than SARS; the number may change as more is learned about the disease.)
What are the Symptoms of a Coronavirus Infection?
Most forms of human coronavirus, including the four most common strains, cause cold- or flu-like symptoms such as a cough, sore throat, and fever. Treatment typically involves rest and over-the-counter medication. In rarer and more severe forms of the virus, such as SARS-CoV and MERS-CoV, patients can develop potentially fatal symptoms such as pneumonia and kidney failure. Though news about 2019-nCoV is still developing, according to the Australian Department of Health, symptoms of 2019-nCoV include fever, headaches, sore throat, coughing, and respiratory illness, which can progress to pneumonia.
The respiratory disease associated with 2019-nCoV is now referred to as COVID-19.
What Do We Know About 2019-nCoV?
Though coronaviruses are zoonotic in origin, most transmission occurs through human-to-human interaction, again similar to the flu or common cold. Coronaviruses have a several-day period in which those infected are contagious but may not show symptoms, increasing the probability that the virus will be spread to others.
Currently, little is known about the origins of 2019-nCoV. The first confirmed cases of the virus appeared in Wuhan, China in late December 2019; the 2019-nCoV virus was identified by Chinese doctors on January 7, 2020.
Very quickly, scientists in China were able to sequence the genome of 2019-nCoV. The virus’s full genome was shared on January 24. According to the CDC, information gathered from the virus’s genome suggests that 2019-nCoV may be related to SARS-CoV or to coronaviruses seen in bats, though this does not necessarily mean that the illness was transmitted from bats to humans. One study of viral proteins conducted by the Northwestern University Feinberg School of Medicine suggests that 2019-nCoV is between 70% and 99% identical to SARS-CoV.
The new virus also behaves similarly to SARS-CoV and MERS-CoV in that it targets lung cells rather than the upper respiratory system, as is seen in less severe forms of human coronavirus, leading to potentially deadly damage to the lungs. Symptoms seem to vary for the disease, and can appear anywhere between two and fourteen days after initial exposure. Patients can spread the virus to others before showing symptoms (asymptomatic).
Spread of 2019-nCoV
By January 20, cases of 2019-nCoV had appeared in Thailand, Japan, and the Republic of Korea. By January 26, nearly 2000 cases had been confirmed in China, with over fifty deaths being attributed to the virus; cases had also been identified in Thailand, Japan, the Republic of Korea, Australia, and the United States, stoking fears about the possibility of a worldwide outbreak similar to that of SARS-CoV in 2003.
According to the CDC, as of February 9 2020, cases of 2019-nCoV have been confirmed in 25 countries:
- ASIA: China, Cambodia, India, Japan, Malaysia, Nepal, the Philippines, Sri Lanka, Singapore, Thailand, the Republic of Korea, United Arab Emirates, Vietnam
- EUROPE: Belgium Finland, France, Germany, Italy, Russia, Spain, Sweden, United Kingdom
- NORTH AMERICA: Canada, United States of America
- OCEANIA: Australia
Several additional regions and territories of China have reported cases, including Hong Kong, Macau, and Taiwan. The slideshow below shows a progression of cases over time.
Within the US, there have been twelve confirmed cases of 2019-nCoV – in the states of Washington, California, Arizona, Wisconsin, Illinois, and Massachusetts.
The first death outside of China occurred in the Philippines; the victim was a man from the Wutan area of China, where the 2019-nCoV outbreak originated. He reportedly died of pneumonia caused by the virus. Additionally, spread of the disease from person-to-person contact (i.e. individuals who have not recently visited Wutan contracting 2019-nCoV from those who have) has been recorded in the United States, Thailand, Germany, France, Japan, and Vietnam.
It is important to note that despite the media coverage of this virus, that many scientists and doctors in the United States argue that US citizens should be more concerned with flu than with 2019-nCoV. The CDC estimates that there have been 31,000,000 cases of flu in the United States since October 2019 and between 12,000 and 30,000 deaths caused or influenced by flu viruses.
The video below from the World Health Organization outlines preventative steps you can take to protect yourself from 2019-nCoV.
We will be updating this page periodically as new information becomes available.
Additional Information:
- CDC Information Page on 2019-nCoV
- WHO Information on 2019-nCoV
- European CDC infographic on coronaviruses.
- RicochetScience additional resources
- Why Vaccinate?
- Animation on How Herd Immunity Works
- Science News : “How the new coronavirus stacks up against SARS and MERS”
article by Kayla Windelspecht
Image Credits
- MERS virus: National Institute of Allergy and Infectious Diseases (NIAID)
- People Wearing Masks: China News Service／中国新闻网 [CC BY (https://creativecommons.org/licenses/by/3.0)]
- Human coronovirus TEM: Dr. Fred Murphy & Sylvia Whitfield/CDC
last updated on Feb 12 ,2020 with new images, names for the virus, and statistics
