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.
To date, the novel coronavirus — currently dubbed “severe acute respiratory syndrome coronavirus 2,” or SARS-CoV-2 for short — has been responsible for more than 1,000,000 infections globally, causing over 70,000 deaths. The U.S. is the most affected country.
But what do we really know about this virus? And how is it likely to affect the global population?
Medical News Today have contacted the WHO, used the information that public health organizations have offered, and looked at the newest studies that have featured in peer-reviewed journals to answer these and other questions from our readers.
Stay informed with live updates on the current COVID-19 outbreak and visit our coronavirus hub for more advice on prevention and treatment.
SARS-CoV-2 is a coronavirus that causes coronavirus disease 2019 (COVID-19). Coronaviruses, in general, are a family of viruses that target and affect mammals’ respiratory systems. According to their specific characteristics, there are four main “ranks” (genera) of coronaviruses, which are called 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 — or Middle East respiratory syndrome coronavirus — which emerged in Saudi Arabia in 2012. This virus has affected at least 2,494 people since then.
When humans do become infected with a coronavirus, this typically happens via contact with an infected animal.
Some of the most common carriers are bats, although 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.
However, later assessments have since suggested that this market was unlikely to be the single source of the coronavirus outbreak, as some of the people infected with the virus had not been frequenting the market.
Specialists have not yet been able to determine the true source of the virus or even confirm whether there was a single original reservoir.
When MNT contacted the WHO for comment, their spokespeople emphasized:
“We don’t yet know [what the specific source of SARS-CoV-2 was]. Researchers in China are studying this but have not yet identified a source.”
While it likely originated in animals, the transmission of the new coronavirus from person to person can occur, though some questions about its transmission remain unanswered.
According to the WHO spokespeople who responded to MNT queries, “[r]esearchers 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, adding:
“As with other coronaviruses, the transmission is through the respiratory route, meaning the virus is concentrated in the airways (nose and lungs) and can pass to another person via droplets from their nose or mouth, for example. We still need more analysis of the epidemiological data to understand the full extent of this transmission and how people are infected.”
In a press briefing from February 6, 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.”
In their “Q&A on coronaviruses,” the WHO 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 — also broadcast on February 6 — Dr. Anthony Fauci, the director of the National Institute of Allergy and Infectious Diseases, said that based on data that 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 give rise to symptoms once it has infected a person.
Although the WHO note that experts estimate that the new virus’s incubation period may last anywhere between 1 and 14 days, they suggest in their coronavirus Q&A section 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 distance from others. This will help slow the spread of the virus from asymptomatic people or people who do not know they have contracted the virus. Cloth face masks should be worn while continuing to practice social distancing. Instructions for making masks at home can be found 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 known as 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 appeared 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 previous coronaviruses, the novel coronavirus causes respiratory disease, and the symptoms affect respiratory health.
According to the Centers for Disease Control and Prevention (CDC), the main symptoms of COVID-19 are fever, cough, and shortness of breath.
“Current information suggests that the virus can cause mild, flu-like symptoms, as well as more severe disease. Most patients 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, WHO officials also pointed out that a runny nose is not usually a symptom of COVID-19.
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In an official WHO Q&A session, Dr. Van Kerkhove explained that as the symptoms of COVID-19 can be very generic, it can be difficult to distinguish between them and the symptoms of other respiratory infections.
To understand exactly what a person is dealing with, she said, specialists test viral samples, checking to see whether the virus’s DNA structure matches that of SARS-CoV-2 or not.
“When someone comes in with a respiratory disease, it’s very difficult — if not impossible — initially to determine what they’re infected with. So, because of this, what we rely on are diagnostics [molecular tests],” said Dr. Van Kerkhove.
The WHO officially changed their classification of COVID-19 from a public health emergency of international concern to a pandemic on March 11.
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 where they can. Some international borders have been completely locked down and in many places travel is being discouraged 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 and 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, the 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%.”
– WHO spokespeople
So far, the number of infections and deaths that COVID-19 has caused is also smaller than the number resulting from recent outbreaks of particularly harmful influenza viruses, such as swine flu (H1N1).
“On H1N1, From April 12, 2009, to April 10, 2010, the CDC estimated there were 60.8 million cases, 274,304 hospitalizations, and 12,469 deaths in the United States due to the (H1N1)pdm09 virus. Additionally, the CDC estimated that 151,700–575,400 people worldwide died from (H1N1)pdm09 virus infection during the first year the virus circulated,” the WHO spokespeople told MNT.
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 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.
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 become infected with 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.
Among adults, some reports suggest that men might be more at risk than women.
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.”
The WHO reports that pregnant women with COVID-19 symptoms should receive priority access to diagnostic tests.
Official WHO prevention guidelines suggest that to avoid infection with the coronavirus, individuals should apply the same best practices for personal hygiene that they would to keep any other virus at bay.
This includes maintaining “at least 1 metre (3 feet) distance between yourself and anyone who is coughing or sneezing.”
According to the WHO spokespeople who replied to MNT queries:
“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, WHO guidelines recommend that people should wear masks if they are coughing or sneezing. Healthy people need only do this if they are caring for someone who has COVID-19.
Masks should cover the nose and mouth and be tightly secured. People should thoroughly wash their hands before putting on a new mask, make sure that they dispose of used masks appropriately, and clean their hands once again after removing them.
There are currently no targeted, specialized treatments for infections resulting from the new coronavirus. When doctors detect a SARS-CoV-2 infection, they aim to treat the symptoms as they arise.
In the WHO Q&A, Dr. Van Kerkhove explained that “[b]ecause 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 also emphasized.
In the same Q&A, Dr. Van Kerkhove 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.
There are currently clinical trials underway 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.
Some scientists are also experimenting with using antiretroviral therapy, which is a treatment for HIV, against the new virus. But why might these kinds of treatments hold any promise when it comes to fighting off this coronavirus?
According to some studies, the combination of antiretroviral drugs that scientists are experimenting with — lopinavir and ritonavir — is able to attack a specialized molecule that HIV and coronaviruses both use to replicate.
Another allegedly promising avenue is using baricitinib — a drug that doctors use to treat arthritis — 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.
But 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, WHO officials explained investigators’ preference for experimenting with existing drugs in fighting off the new coronavirus.
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 trials and clinical trials that new drugs require, which can take a very long time indeed.
