SARS-CoV-2 is a coronavirus that causes coronavirus disease 2019 (COVID-19). Coronaviruses are a family of viruses that target and affect mammals’ respiratory systems. According to their specific characteristics, there are four main ranks, or genera, of coronavirus: alpha, beta, delta, and gamma.
Most of these only affect animals, but a few can also pass to humans. Those that are transmissible to humans belong to only two of these genera: alpha and beta.
Only two coronaviruses have previously caused global outbreaks. The first of these was the SARS coronavirus — responsible for severe acute respiratory syndrome (SARS) — which first started spreading back in 2002, also in China. The SARS virus epidemic primarily affected the populations of mainland China and Hong Kong, and it died off in 2003.
The other one was the MERS coronavirus — responsible for Middle East respiratory syndrome (MERS) — which emerged in Saudi Arabia in 2012. This virus has affected at least 2,494 people since then.
When humans do contract a coronavirus, it typically happens due to contact with an infected animal.
Some of the most common carriers are bats, though they do not typically transmit coronaviruses directly to humans. Instead, the transmission might occur via an intermediary animal, which will usually — though not always — be a domestic one.
The SARS coronavirus spread to humans via civet cats, while the MERS virus spread via dromedaries. However, it can be difficult to determine the animal from which a coronavirus infection first starts spreading.
In the case of the new coronavirus, initial reports from China tied the outbreak to a seafood market in central Wuhan. As a result, local authorities closed down the market on January 1, 2020.
However, later assessments have suggested that this market was unlikely to be the single source of the coronavirus outbreak, as some of the people with the virus had not been frequenting it.
Specialists have not yet been able to determine the true source of the virus or even confirm if there was a single original reservoir.
Although it likely originated in animals, the virus does transmit from person to person. However, some questions about its transmission remain unanswered.
According to WHO spokespeople, “Researchers are still studying the exact parameters of human-to-human transmission.”
“In Wuhan at the beginning of the outbreak, some people became ill from exposure to a source, most likely an animal, carrying the disease. This has been followed by transmission between people,” they explained.
In a press briefing from February 6, 2020, WHO consultant Dr. Maria Van Kerkhove said that, for now, “[w]e do know that mild individuals shed virus, we know that severe individuals shed virus. […] We know that the more symptoms you have, the more likely you are to transmit.”
The WHO also state that “[t]he risk of catching COVID-19 from someone with no symptoms at all is very low. However, many people with COVID-19 experience only mild symptoms. […] It is therefore possible to catch COVID-19 from someone who has, for example, just a mild cough and does not feel ill.”
In an interview for the JAMA Network broadcast on February 6, 2020, Dr. Anthony Fauci — the director of the National Institute of Allergy and Infectious Diseases — said that based on data they have received from Chinese specialists, the new coronavirus’s “incubation period is probably between 5 and 6 — maybe closer to 5 — days.“
That is, the virus likely takes about 5–6 days to cause symptoms once it has infected a person.
Although the WHO say that experts estimate that the new virus’s incubation period may last anywhere between 1 and 14 days, they suggest that the most likely duration is about 5 days.
The CDC recommend that all people wear cloth face masks in public places where it is difficult to maintain a 6-foot (2-meter) distance from others. This will help slow the spread of the virus from asymptomatic people and people who do not know that they have contracted it. People should wear cloth face masks while continuing to practice physical distancing. Instructions for making masks at home are available here. Note: It is critical that surgical masks and N95 respirators are reserved for healthcare workers.
Researchers from Chinese institutions were able to use state-of-the-art genome sequencing tools to identify the DNA structure of the novel coronavirus.
It has emerged that SARS-CoV-2 is most similar to two bat coronaviruses: bat-SL-CoVZC45 and bat-SL-CoVZXC21. Its genomic sequence is 88% the same as theirs.
The same study shows that the new virus’s DNA is about 79% the same as that of the SARS coronavirus and approximately 50% like that of the MERS virus.
Recently, a study by researchers in China suggested that pangolins may have been the initial propagators of SARS-CoV-2, as its genomic sequence appears to be 99% like that of a coronavirus specific to these animals.
Since then, however, other specialists have cast doubts over this idea, citing inconclusive evidence.
Like other coronaviruses, the novel coronavirus causes respiratory disease, and the symptoms affect a person’s respiratory health.
According to the Centers for Disease Control and Prevention (CDC), the main symptoms of COVID-19 are a fever, a cough, and shortness of breath.
“Current information suggests that the virus can cause mild, flu-like symptoms, as well as more severe disease. Most [people] seem to have mild disease, and about 20% appear to progress to more severe disease, including pneumonia, respiratory failure, and, in some cases, death,” WHO spokespeople told MNT.
In their press briefing from February 27, 2020, WHO officials also pointed out that a runny nose is not usually a symptom of COVID-19.
The WHO officially changed their classification of COVID-19 from a public health emergency of international concern to a pandemic on March 11, 2020.
In a declaration, WHO’s director general, Dr. Tedros Adhanom Ghebreyesus, stated that:
“WHO has been assessing this outbreak around the clock and we are deeply concerned both by the alarming levels of spread and severity, and by the alarming levels of inaction.We have therefore made the assessment that COVID-19 can be characterized as a pandemic.Pandemic is not a word to use lightly or carelessly. It is a word that, if misused, can cause unreasonable fear, or unjustified acceptance that the fight is over, leading to unnecessary suffering and death.Describing the situation as a pandemic does not change WHO’s assessment of the threat posed by this virus. It doesn’t change what WHO is doing, and it doesn’t change what countries should do.”
The global implications have been severe. Many countries have closed schools and are recommending that people work from home when they can. Some countries have completely locked down their international borders and are discouraging travel unless it is deemed essential.
In the U.S., the White House is advising that people avoid social gatherings of more than 10 people, while individual states have introduced their own measures to try to deal with the situation.
Many questions also remain about how SARS-CoV-2 compares with other viruses in terms of its rates of infection and mortality.
In response to questions about this, WHO spokespeople told MNT that “[t]his is a new disease, and our understanding is changing rapidly. We will continue to analyze information on both current and any new cases.”
“We don’t yet know many details about the mortality rate from SARS-CoV-2, and studies are ongoing now. With MERS, we know that approximately 35% of reported patients with [MERS coronavirus] infection have died. For SARS, WHO estimated that the case fatality ratio of SARS ranges from 0% to 50% depending on the age group affected, with an overall estimate of case fatality of 14% to 15%.”
According to recent assessments, SARS-CoV-2 seems to be more infectious than other coronaviruses — such as those that cause SARS and MERS — but less likely to lead to death.
Some estimates suggest that the death rate of the new coronavirus is in the range of 2–3%, but there are no official numbers in this regard, as it is hard to tell how the outbreak will develop.
The WHO report that the two groups most at risk of experiencing severe illness due to a SARS-CoV-2 infection are older adults and individuals who have other health conditions that compromise their immune system.
The report also notes that “[t]he risk of severe disease gradually increases with age starting from around 40 years.”
Other reports note that very few children have contracted the new coronavirus. However, a recent preliminary study — not yet peer reviewed or published in a journal — claims that children face the same risk of infection as adults, and the CDC reinforce this.
Among adults, some reports suggest that males might be more at risk than females, though neither the WHO nor the CDC include being male as a risk factor.
Although there are currently no published scientific reports about the susceptibility of pregnant women, the CDC note that:
“Pregnant [women] have had a higher risk of severe illness when infected with viruses from the same family as COVID-19 and other viral respiratory infections.”
The CDC also recommend that infants born to mothers with suspected or confirmed COVID-19 go into isolation.
Mother-to-child transmission is unlikely during pregnancy. A very small number of babies have tested positive for the virus, but it is not clear whether they contracted the virus before or after birth.
The WHO report that pregnant women with COVID-19 symptoms should receive priority access to diagnostic tests.
Official WHO prevention guidelines suggest that in order to avoid contracting coronavirus, people should apply the same best practices for personal hygiene that they would to keep any other virus at bay.
The CDC recommend maintaining a distance of 6 feet (2 meters) from other people.
According to WHO spokespeople:
“Standard recommendations to prevent infection spread include regular hand-washing, covering [the] mouth and nose when coughing and sneezing, [and] thoroughly cooking meat and eggs. Avoid close contact with anyone showing symptoms of respiratory illness, such as coughing and sneezing.”
As for wearing protective masks, the CDC recommend that everyone wear a cloth face covering when out in public, such as when going to the grocery store. This is to slow the spread of the virus and prevent people who do not know that they have the virus from transmitting it.
Face coverings should cover the nose and mouth and be very secure. They should include multiple layers of fabric and allow unrestricted breathing. When removing the covering, be careful not to touch the eyes, nose, or mouth. Wash the hands immediately after removing it.
When using a cloth face covering, people should wash them regularly in the washing machine.
People can find out how to make face coverings at home here.
There are currently no targeted, specialized treatments for COVID-19. When doctors detect a SARS-CoV-2 infection, they aim to treat the symptoms as they arise.
As Dr. Van Kerkhove explained: “Because this is a new virus, we don’t have specific treatments for that virus. But because this virus causes respiratory disease, those symptoms are treated.“
“Antibiotics won’t work against a virus,” she added.
Dr. Van Kerkhove also noted that “there are treatments that are in development” for the new coronavirus. Over the years, she said, “many treatments [have been] looked at to treat other coronaviruses, like the MERS coronavirus.”
“And hopefully, those treatments can [also] be useful for the novel coronavirus,” she continued.
Clinical trials are under way to find a treatment and a vaccine against the MERS coronavirus, which, if successful, could lay the groundwork for a SARS-CoV-2 vaccine and COVID-19 treatment.
Scientists are currently investigating the drug remdesivir against SARS-CoV-2. This is an intravenous drug with broad antiviral abilities. Research has shown some potential against SARS-CoV-2 and other coronaviruses.
They are also investigating hydroxychloroquine and chloroquine, which are prescription drugs for treating malaria and some inflammatory conditions. Researchers are looking at their ability to both prevent and treat COVID-19.
Other drugs, including antiretroviral drugs for treating HIV, are also under investigation.
Another potentially promising avenue is using baricitinib, an arthritis drug, against the new coronavirus. The researchers who came up with this idea explain that it is likely that SARS-CoV-2 can infect the lungs by interacting with specific receptors present on the surface of some lung cells.
However, such receptors are also present on some cells in the kidneys, blood vessels, and heart. Baricitinib, the researchers say, may be able to disrupt the interaction between the virus and these key receptors. However, whether or not it will really be effective remains to be seen.
In a press briefing from February 5, 2020, WHO officials explained investigators’ preference for experimenting with existing drugs.
Such drugs, they said, have already gained official approval for use against other specifications, meaning that they are largely safe. As a result, they need not go through the extensive series of preclinical and clinical trials that new drugs require, which can take a very long time.
To get more information about the current outbreak and for extensive guidelines about best practices, here are a few international resources:
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