Coronavirus has infected tens of thousands of patients around the world, yet little is still known about the highly contagious illness.
An outbreak of the flu-like disease, now known as Covid-19, first emerged among a cluster of pneumonia patients in Wuhan, China in late December and it has rapidly spread to Europe and the Americas.
The latest studies have found that infected people can pass coronavirus on to others before they even know that they have it, and it takes about five days before signs such as a high fever or a cough to appear.
This new strain of coronavirus ravages the human body – putting the elderly and patients with pre-existing conditions at risk of death – and experts believe it can live inside respiratory tracts for at least five weeks.
The global pandemic has led to travel bans and border closures, the shuttering of buildings such as schools and museums, and put the entire country of Italy and its 60million residents under an unprecedented lockdown.
Amid drastic measures to curb the spread of Covid-19, there is no vaccine or specific treatment, and researchers are still learning about how it attacks the body, how it can be treated and if there are any long-term effects.
Many of the answers so far have been coming from doctors in China and specifically Wuhan and surrounding Hubei province, which were ground zero for the outbreak.
What does coronavirus do to the body?
Coronavirus infects the tissues and airways deep inside the lungs.
Symptoms resemble the flu and include fever, dry cough, fatigue and shortness of breath.
Some people suffer muscle pain, a sore throat, a runny nose or diarrhea.
The disease can progress to pneumonia – a lung infection – and cause severe lung damage or organ failure in severe cases.
In the most severe cases, a patient can develop acute respiratory distress syndrome and die.
CT scans of coronavirus patients’ lungs show white patches, which indicate ground-glass opacity, or fluid.
In one case, a 44-year-old man, who worked at the Wuhan seafood market where the virus was initially thought to have been passed to humans, went to a hospital after suffering a high fever and cough for almost two weeks on December 25 last year.
A chest CT scan showed white patches and scans taken later showed the opacities had spread significantly.
The man was diagnosed with severe pneumonia and acute respiratory distress syndrome, but he died a week later.
In the US, doctors at Mount Sinai Hospital in New York City were the first in America to analyze CT scans of Covid-19 sufferers.
The doctors said they identified specific patterns in the lungs of dozens of patients who were hospitalized in China at the height of the epidemic there.
The ground glass opacities, or patches, became denser over time, and the patterns were similar to those found in patients who contracted SARS or MERS.
The doctors found “fully involved lung disease” in 25 patients who had scans between six and 12 days after they reported symptoms.
Connor Reed, 25, was the first British person to contract the illness. He caught it in Wuhan, where he works as an English teacher.
Mr Reed, originally from Llandudno, North Wales, has told how he feared he would die and he felt like he was “suffocating” and his lungs sounded like “a paper bag being crumpled up”.
He was hospitalized and weeks later tested positive for coronavirus as the illness spread and was identified in China.
The UK’s Department of Health says on its website: “Typical symptoms of coronavirus include fever and a cough that may progress to severe pneumonia causing shortness of breath and breathing difficulties.
“Generally, coronavirus can cause more severe symptoms in people with weakened immune systems, older people, and those with long-term conditions like diabetes, cancer, and chronic lung disease.”
How many people will die?
British health chiefs say most people who contract coronavirus will only suffer mild symptoms.
According to the World Health Organisation, about 80 percent of patients recover without requiring specialist treatment.
About one in six suffers a serious case and suffers breathing difficulties.
Professor Chris Whitty, England’s chief medical officer, said about one percent of coronavirus patients in the UK could die.
Those who are most at risk include the elderly and people with underlying health conditions.
What are the long-term effects?
The virus is still very new and doctors are still studying the potential long-term effects.
Some signs have emerged during a recent study in Hong Kong, where more than 130 people have been diagnosed.
Doctors there said some patients who have recovered from Covid-19 are now suffering from reduced lung function – by as much as 30 percent – and can no longer do some of the activities they enjoyed in the past.
Some are left gasping for air when they walk quickly, said Dr. Owen Tsang Tak-yin, head of the Infectious Disease Centre at Princess Margaret Hospital.
He added: “Some patients might have around a drop of 20 to 30 percent in lung function.”
How is it spread?
Experts are still investigating, but it is is spread by droplets in an infected person’s coughs or sneezes, which can be brought in through the mouth, nose or eyes of others.
Spiked coronavirus particles invade human cells and multiply, causing the infection to develop and spread through the body.
Once in the lungs, the virus can cause serious damage and become life-threatening.
According to researchers, the lungs can fill with fluid and dead cells, and make it harder for the lungs to supply oxygen to the blood and remove carbon dioxide.
The NHS said: “Because it’s a new illness, we do not know exactly how coronavirus spreads from person to person.
“Similar viruses are spread in cough droplets.
“It’s very unlikely it can be spread through things like packages or food.”
Health officials said the virus can live on hard surfaces such as plastic for up to 72 hours and soft surfaces for about 24 hours.
How is it treated?
There is no specific treatment for coronavirus and it could be a year before a vaccine is rolled out for public use.
The NHS said: “Antibiotics do not help, as they do not work against viruses.
“Treatment aims to relieve the symptoms while your body fights the illness.
“You’ll need to stay in isolation, away from other people, until you have recovered.”
In Italy, doctors have been forced to make life-or-death decisions, ultimately overlooking elderly and sicker patients and leaving them to die while focusing on saving younger people or those who have a better chance of recovering.
What do I do if I have symptoms?
The Department of Health is telling people to stay home for seven days if they have a high temperature and a new, continuous cough.
“This will help to protect others in your community while you are infectious,” it said.
Do not go to a GP surgery, pharmacy or hospital.
Call an ambulance to pick you.
The Department of Health added: “You do not need to contact NHS 111 to tell them you’re staying at home. We will not be testing people who are self-isolating with mild symptoms.”