What Is a Coronavirus?

Coronaviruses(Coronavirus) are a family of viruses known for containing strains that cause potentially deadly diseases in mammals and birds. In humans, they’re typically spread via airborne droplets of fluid produced by infected individuals.

Some rare but notable strains, including Wuhan coronavirus (2019-nCoV), and those responsible for severe acute respiratory syndrome (SARS) and the Middle East respiratory syndrome (MERS), can cause death in humans.

First described in detail in the 1960s, the coronavirus gets its name from a distinctive corona or ‘crown’ of sugary-proteins that projects from the envelope surrounding the particle. Encoding the virus’s make-up is the longest genome of an RNA-based virus – a single strand of nucleic acid roughly 26,000 to 32,000 bases long.

There are four known genera in the family, named Alphacoronavirus, Betacoronavirus, Gammacoronavirus, and Deltacoronavirus. The first two only infect mammals, including bats, pigs, cats, and humans. Gammacoronavirus mostly infects birds such as poultry, while Deltacoronavirus can infect both birds and mammals.

What are the symptoms of a coronavirus?

Coronaviruses can give rise to a variety of symptoms in different animals. While some strains cause diarrhea in pigs and in turkeys, most of the time infections can be compared to a bad cold, causing mild to moderate upper respiratory problems such as a runny nose and sore throat.

There are a handful of lethal exceptions, which have had a devastating impact on livestock and human health around the globe.

Wuhan coronavirus (2019-nCoV)

Wuhan coronavirus was first identified in the Chinese city of Wuhan in 2019. At the time of writing, numbers of infected are still on the rise, with a number of deaths having been reported.

Snakes have been suspected as a potential source for the outbreak, though other experts currently consider this as unlikely.

Severe acute respiratory syndrome (SARS-CoV):

SARS was first recognized as a distinct strain of coronavirus in 2003. The source of the virus has never been clear, though the first human infections can be traced back to the Chinese province of Guangdong in 2002.

The virus then became a pandemic, causing more than 8,000 infections of an influenza-like disease in 26 countries with close to 800 deaths.

The Middle East respiratory syndrome (MERS-CoV):

MERS was first identified in Saudi Arabia in 2012 in people displaying symptoms of fever, cough, shortness of breath and occasionally gastrointestinal problems such as diarrhea. An animal source for the virus has never been officially confirmed, though evidence points to dromedary camels as a potential reservoir of infection.

The World Health Organisation has identified around 2,500 cases of infection in 27 countries since initial outbreaks, resulting in nearly 860 deaths.

Coronavirus: What it does to the body

How does it attack the body? What is the full range of symptoms? Who is more likely to be seriously ill or die? How do you treat it?

Now, an account by medics on the front line of this epidemic, at the Jinyintan Hospital, in Wuhan, is starting to provide answers.

A detailed analysis of the first 99 patients treated there has been published in The Lancet medical journal.

Lung assault:

All of the 99 patients taken to the hospital had pneumonia – their lungs were inflamed and the tiny sacs where oxygen moves from the air to the blood were filling with water.

Other symptoms were:

• 82 had fever
• 81 had a cough
• 31 had shortness of breath
• 11 had muscle ache
• nine had confusion
• eight had a headache
• five had a sore throat

First deaths:

The first two patients to die were seemingly healthy, although they were long-term smokers and that would have weakened their lungs.

The first, a 61-year-old man, had severe pneumonia when he arrived at the hospital.

He was in acute respiratory distress, meaning his lungs were unable to provide enough oxygen to his organs to keep his body alive.

Despite being put on a ventilator, his lungs failed and his heart stopped beating.

He died 11 days after he was admitted.

The second patient, a 69-year-old man, also had acute respiratory distress syndrome.

He was attached to an artificial lung or ECMO (extracorporeal membrane oxygenation) machine but this wasn’t enough.

He died of severe pneumonia and septic shock when his blood pressure collapsed.

At least 10% die:

As of 25 January, of the 99 patients:

• 57 were still in the hospital
• 31 had been discharged
• 11 had died

This does not mean the death rate of the disease is 11%, though, as some of those still in a hospital may yet die and many others have such mild symptoms they do not end up in a hospital.

Market workers: (Coronavirus)

Live animals sold at the Huanan seafood market are thought to be the source of the infection, called 2019-Nov.

And 49 out of the 99 patients had a direct connection to the market:

• 47 worked there, either as managers or manning the stalls
• two were shoppers who had only popped in

Middle-aged men worst affected:

Most of the 99 patients were middle-aged, with an average age of 56 – and 67 of them were men.

However, more recent figures suggest a more even gender split. The China Centers for Disease Control and Prevention said 1.2 men were infected for every 1.0 women.

There are two possible explanations for the difference:

• Men could be more likely to become severely ill and need hospital treatment
• Men, for social or cultural reasons, may have been more likely to be exposed to the virus at the beginning of the outbreak

Dr. Li Zhang, at the hospital, says: “The reduced susceptibility of females to viral infections could be attributed to the protection from X chromosome and sex hormones, which play an important role in immunity.”

And those who were already sick:

Most of the 99 had other diseases that may have made them more vulnerable to the virus as a “result of the weaker immune functions of these patients”:

• 40 had a weak heart or damaged blood vessels due to conditions including heart disease, heart failure, and stroke
• A further 12 patients had diabetes