The coronavirus only emerged in December last year, but the world is already grappling with a pandemic of the virus and the disease it causes – Covid-19.
For most, the disease is mild, but some people die.
So how does the virus attack the body, why are some people killed and how is it treated?
At this point, the virus establishes itself.
Viruses work by entering the cells that make up your body and then hijacking them.
The coronavirus, officially called Sars-CoV-2, can enter your body if you breathe it in (after someone nearby coughs) or if you touch a contaminated surface and then your face.
It first infects the cells lining your throat, airways and lungs, turning them into “coronavirus factories” that spew out large numbers of new viruses, which then infect even more cells.
You don’t get sick at this early stage, and some people may never develop symptoms.
The incubation period, the time between infection and the first symptoms, varies greatly, but averages five days.
This is all most people will experience.
Covid-19 is a mild infection for eight in 10 people who get it, and the core symptoms are fever and cough.
Body aches, sore throats and headaches are possible but not guaranteed.
The fever and general feeling of being nauseous are due to your immune system reacting to the infection. It has recognized the virus as a hostile invader and signals the rest of the body that something is wrong by releasing chemicals called cytokines.
These boost the immune system but also cause body aches, pains and fever.
The coronavirus cough is initially dry (you don’t bring anything up), and this is likely due to irritation of the cells as they become infected with the virus.
Some people will eventually start coughing up sputum — a thick mucus that contains dead lung cells that have been killed by the virus.
These symptoms are treated with bed rest, plenty of fluids, and acetaminophen. You do not need specialist medical care in the hospital.
This phase lasts about a week – at this point most recover because their immune systems have fought off the virus.
However, some will develop a more serious form of Covid-19.
This is the best we know about this stage at the moment, but there are studies that suggest the disease can also cause more cold-like symptoms like a runny nose.
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As the disease progresses, it is due to the immune system overreacting to the virus.
These chemical signals to the rest of the body cause inflammation, but this needs to be delicately balanced. Too much inflammation can cause collateral damage throughout the body.
“The virus triggers an imbalance in the immune response, there’s too much inflammation, how it does that we don’t know,” said Dr. Nathalie MacDermott from King’s College London.
Pneumonia is called pneumonia.
If it were possible to travel through your mouth, down the windpipe, and through the tiny tubes in your lungs, you would eventually end up in tiny air sacs.
This is where oxygen gets into the blood and carbon dioxide gets out, but when you get pneumonia, the tiny sacs start to fill with water and can eventually cause shortness of breath and difficulty breathing.
Some people need a ventilator to help them breathe.
Based on data from China, this stage is thought to affect around 14% of people.
It is estimated that around 6% of cases become critically ill.
At this point the body begins to fail and there is real danger of death.
The problem is that the immune system is now spiraling out of control, causing damage throughout the body.
It can lead to septic shock when blood pressure drops to dangerously low levels and organs stop functioning properly or fail completely.
Acute respiratory distress syndrome, which is caused by widespread inflammation in the lungs, prevents the body from getting enough oxygen it needs to survive. It can prevent the kidneys from cleaning the blood and damage the lining of the gut.
“The virus causes so much inflammation that you succumb … it becomes multi-organ failure,” said Dr. Bharat Pankhania.
And if the immune system can’t get a handle on the virus, it will eventually spread to every corner of the body, where it can do even more damage.
Treatment at this stage is highly invasive and may include ECMO or extracorporeal membrane oxygenation.
This is essentially an artificial lung that takes blood from the body through thick tubes, oxygenates it, and pumps it back in.
But eventually the damage can reach fatal proportions, at which point the organs can no longer keep the body alive.
Doctors have described how some patients died despite their best efforts.
The first two patients to die at Jinyintan Hospital in Wuhan, China appeared healthy, although they were long-time smokers and it would have weakened their lungs.
The first, a 61-year-old man, had severe pneumonia when he was hospitalized.
He was suffering from acute shortness of breath, and although he was on a ventilator, his lungs failed and his heart stopped beating.
He died 11 days after his admission.
The second patient, a 69-year-old man, also had acute respiratory distress syndrome.
He was hooked up to an ECMO machine, but that wasn’t enough. He died of severe pneumonia and septic shock when his blood pressure collapsed.
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