Corona viruses are types of viruses that typically affect the respiratory tracts of birds and mammals, including humans. Doctors associate them with the common cold, bronchitis, pneumonia, severe acute respiratory syndrome (SARS), and COVID-19. They can also affect the gut.
These viruses are typically responsible for common colds more than serious diseases. However, corona viruses are also behind some more severe outbreaks.
Over the last 70 years, scientists have found that corona viruses can infect mice, rats, dogs, cats, turkeys, horses, pigs, and cattle. Sometimes, these animals can transmit corona viruses to humans.
Most recently, authorities identified a new corona virus outbreak in China that has now reached other countries. It has the name corona virus disease 2019, or COVID-19.
In this article, we explain the different types of human corona viruses, their symptoms, and how people transmit them. We also focus on three particularly dangerous diseases that have spread due to corona viruses: COVID-19, SARS, and MERS.
Scientists first found evidence of human corona viruses (HCoV) in the 1960s in the noses of people with the common cold. Two human corona viruses are responsible for a large proportion of common colds: OC43 and 229E.
The name “corona virus” comes from the crown-like projections on their surfaces. “Corona” in Latin means “halo” or “crown.”
Among humans, corona virus infections most often occur during the winter months and early spring. People regularly become ill with a cold due to a corona virus and may catch the same one about 4 months later.
This is because corona virus antibodies do not last for a long time. Also, the antibodies for one strain of corona virus may be ineffective against another one.
In 2019, the Centers for Disease Control and Prevention (CDC) started monitoring the outbreak of a new corona virus, SARS-CoV-2, which causes the respiratory illness now known as COVID-19. Authorities first identified the virus in Wuhan, China.
Since then, the virus has spread to other countries, both in and outside Asia, leading the World Health Organization (WHO) to declare this as a pandemic.
As of March 23, more than 340,000 people have contracted the virus worldwide, causing over 14,000 deaths.
In the U.S., the virus has affected over 35,000 people, resulting in more than 450 deaths.
The first people with COVID-19 had links to an animal and seafood market. This fact suggested that animals initially transmitted the virus to humans. However, people with a more recent diagnosis had no connections with or exposure to the market, confirming that humans can pass the virus to each other.
Information on the virus is scarce at present. In the past, respiratory conditions that develop from corona viruses, such as SARS and MERS, have spread through close contacts.
On February 17, 2020, the Director-General of the WHO presented at a media briefing the following updates on how often the symptoms of COVID-19 are severe or fatal, using data from 44,000 people with a confirmed diagnosis:
|Stage of severity||Rough percentage of people with COVID-19|
|Mild disease from which a person can recover||More than 80%|
|Severe disease, causing breathlessness and pneumonia||Around 14%|
|Critical disease, including septic shock, respiratory failure, and the failure of more than one organ||About 5%|
The WHO reports that the two groups most at risk of experiencing severe illness due to a SARS-CoV-2 infection are older adults, defined as “over 60 years old”, and individuals who have other health conditions that compromise their immune system.
According to the CDC, children are not at higher risk for COVID-19 than adults.
While there are currently no published scientific reports about the susceptibility of pregnant women, the CDC notes that:
“Pregnant women experience immunologic and physiologic changes which might make them more susceptible to viral respiratory infections, including COVID-19.”
The CDC also recommend that infants born to mothers with suspected or confirmed COVID-19 are placed in isolation as a “person under investigation.”
Symptoms of COVID-19
Symptoms vary from person-to-person with COVID-19. It may produce few or no symptoms. However, it can also lead to severe illness and may be fatal. Common symptoms include:
- potential loss of taste or smell
It may take 2–14 days for a person to notice symptoms after infection.
No vaccine is currently available for COVID-19. However, scientists have now replicated the virus. This could allow for early detection and treatment in people who have the virus but are not yet showing symptoms.
The National Institutes of Health (NIH) suggest that several groups of people have the highest risk of developing complications due to COVID-19. These groups include:
- young children
- people aged 65 years or older
- women who are pregnant
The CDC advise that although there have been reports of complications in young children, these are rare. COVID-19 most commonly produces mild symptoms in children.