Psychosis and stroke: The shocking COVID complications
A year after it emerged in China, COVID-19 has killed over 1.7 million people and wreaked economic devastation.
More than 77.8 million people have been infected but vaccines developed in record time could soon stop the illness.
Twelve months on we take stock of what we've learned about the virus, how it spreads, how it affects every major organ in the body and how your sex, your blood type and even your genes determine how it will affect you.
The virus has caused psychosis, delivered vastly different outcomes in identical twins who live and work in the same place and, yes, you can get reinfected.
HOW IT SPREADS
The secret to the success of the SARS-CoV-2 virus behind the pandemic is that it's tricky enough to spread before people have symptoms and some people have no symptoms at all.
We now know the virus is spread through the air as well as on surfaces touched by infected people. Wearing a mask can help stop you getting infected and prevent you spreading it to others.
It takes on average five days for symptoms to emerge and 97.5 per cent of people who develop symptoms do so within 11.5 days.
The virus gets into our bodies by latching onto a receptor called ACE2 on human cells.
Although scientists have found people shed the virus for up to 83 days it ceases to be infectious nine days after symptoms start.
WHAT ARE THE SYMPTOMS
The most common symptoms are loss of smell, fever, dry cough, and shortness of breath but some people experience nausea, vomiting, diarrhoea, headache and fatigue.
Eight in ten people with COVID become only mildly ill and one in five are at risk of severe disease.
Around 5 per cent of patients with COVID-19 experience severe symptoms and around 75 per cent of patients hospitalised with COVID-19 require oxygen.
HOW THE VIRUS AFFECTS THE BODY
Initially it was thought COVID-19 was a respiratory illness. Now we know it affects the heart, brain, gut, kidneys, liver, nervous system, eyes and even the skin.
The Journal of the American Medical Association (JAMA) reported the risk of a heart attack, stroke or heart failure is 12 times higher in COVID patients, and COVID patients are nine to 10 times more likely to develop diabetes or kidney disease.
It can even cause psychosis and one woman with COVID claimed to have seen lions and monkeys in her house, became disoriented and aggressive towards others, and was convinced that her husband was an impostor.
JAMA said three in four people hospitalised with the virus develop pneumonia, one in six have acute respiratory distress and one in five develop acute liver injury. A quarter of all COVID patients have heart failure, one in 12 suffer impaired consciousness and 3 per cent endure acute brain disease.
Rare complications among critically ill patients with COVID-19 include cytokine storm, where the body's immune system attacks the major organs.
Doctors in the UK also reported a phenomenon they called "sticky blood' in COVID patients who have blood clotting factors five times higher than normal.
Doctors in New York reported the virus caused diabetes in some people who developed high blood sugar even if they had never been diagnosed with diabetes before.
Worldwide the virus has killed more than 1.7 million people including 900-plus Australians.
The Australian Bureau of Statistics (ABS) reported in August the case fatality rate for Australia - the number of deaths divided by the number of reported cases - at 2.7 per cent.
This compared to a case fatality rate of 1.8 per cent in the US and 3.3 per cent in the UK.
The death rate from COVID-19 is far higher than for influenza which kills just 0.1 per cent of people in the US.
WHO GETS IT WORST
Men, the elderly and those who have diabetes or are overweight are most at risk from COVID-19.
Men are nearly three times more likely to be admitted to intensive care and 1.39 times more likely to die.
In Australia more women than men have died from the virus but men aged under 80 were twice as likely to die as women.
It's thought this is because men have higher levels of immune proteins that trigger inflammation and more ACE2 receptors the virus uses to enter the body.
Fat tissue contains a lot of ACE2 receptors and this is why people who are overweight are more at risk.
The risk of dying from COVID-19 is three times higher for people with type 1 diabetes and almost twice as high for type 2, versus those without diabetes.
Three in four deaths are among people aged over 80 because their immune systems are degraded and they are more likely to have other health conditions that place them at risk.
COULD YOUR BLOOD TYPE AFFECT COVID-19?
One study suggests people with blood group O are slightly less likely to catch COVID-19.
CAN YOUR GENES AFFECT THE DISEASE
A gene which determines a person's blood type, another that rallies the immune system, a gene known to be involved in lung disease and another involved in inflammation could have a role in severe COVID-19.
The case of twins who had vastly different outcomes from COVID-19 suggests factors other than genes play a role.
Two 60-year-old identical twins who lived at the same address in the US and worked at the same location repairing cars had vastly different outcomes.
Twin one was discharged without complications and recovered uneventfully while twin two ended up in ICU on a ventilator, he developed septic shock but eventually recovered.
Children do get COVID-19 but most cases have been mild because their immune system is stronger and one in four never develop any symptoms.
Research suggests children have fewer ACE2 receptors on their cells than older people, these are the receptors the virus needs to enter the body.
A small number of children in Europe and the US developed an inflammatory syndrome similar to Kawasaki disease but they responded to treatment.
The majority of people who contract COVID have symptoms for over a month but around one in ten people develop "Long COVID".
These people suffer fatigue and brain fog, aches and pains, headaches, chest pain as well, liver dysfunction and ongoing shortness of breath for three months or more.
Being female, overweight, having asthma and being aged over 50 raises the risk of Long COVID so does having more than five different symptoms in the first week.
IMMUNITY AND RE-INFECTION
A study of 30,000 people and found that most of those who had the virus and experienced mild-to-moderate disease had robust antibodies lasting at least five months.
But fears people can be reinfected have been realised.
In August, a 33 year old man from Hong Kong was the first proven case of reinfection.
A US citizen tested positive again 48 days after recovering and after his second infection he needed oxygen support and was hospitalised.
There was a similar case in Ecuador and in the Netherlands an 89-year-old woman receiving chemotherapy was reinfected 59 days after her first bout and died.
Two Indian healthcare workers in their twenties tested positive for a second time but they were asymptomatic both times.
COVID-19 has mutated since the beginning of the year and a variant known as D614G which was more easily transmissible was the dominant strain by the middle of the year.
A new strain UK authorities claim is 70 per cent more infectious emerged in the South of England in October.
Experts say there is no evidence either strain causes more serious infection or that vaccines won't work against them.
A cheap steroid called Dexamethasone is one of the most effective treatments reducing death by 17 per cent.
The experimental antiviral drug Remdesivir given to US president Donald Trump shortens recovery by five days.
A drug called Regeneron also given to Donald Trump and a similar drug made by Eli Lily have been approved to treat people with early stage mild disease because they significantly reduce viral load.
Despite the hype, anti malaria drug Hydroxychloroquine and HIV treatments lopinavir-ritonavir do not reduce death or severe disease.
The blood or plasma from people who had recovered from the virus had been proposed as a possible treatment but there is no evidence this works.
Originally published as Psychosis and stroke: rare COVID complications