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It remains unclear how deadly the new strain of coronavirus (Covid-19) is, or if it can be stopped from spreading around the world as a pandemic.
We do know it is nothing like as dangerous as diseases such as Ebola, which kills up to two thirds of those who catch it, but doctors remain unsure of its medical severity.
This article details the latest evidence on the severity of disease, treatment of patients and the tactics the UK authorities are using to try and slow its spread and reduce its impact.
How dangerous is coronavirus?
This remains the million dollar question. In Wuhan - the epicentre of the Covid-19 outbreak - the current death rate is between 2 and 4 per cent but is around 0.7 per cent outside the city, according to the World Health Organisation (WHO).
If it falls as low as the 0.026 per cent death rate for swine flu in 2009, it should be manageable even if it spreads throughout Britain. The “reasonable worst case scenario” the British government plans for with respiratory disease outbreaks is a death rate of 2.5 per cent - the same as for the Spanish Flu outbreak of 1918 and the worst in modern history.
What are doctors most worried about?
Even with the medical data now pouring out of China and other affected countries experts are still far from sure about the clinical severity of the disease or how to treat it.
It is known that the virus is more likely to kill the elderly and those with underlying health conditions in the same way as seasonal flu does. However, a not insignificant number of healthy young people have died too - and this is what is worrying doctors around the world.
How does the virus attack the body?
For the vast majority of people - over 80 per cent - the virus will cause only mild symptoms and pass like a common cold. But a significant number of cases are “severe”, with the virus attacking the lungs and causing pneumonia.
Doctors in Singapore, where there have been more than 80 cases, say the disease presents in a similar way to severe acute respiratory syndrome (Sars), although it remains much less lethal.
The virus attacks the lungs and progresses in distinct phases. CT scans of the lungs scans show “ground-glass” opacity and then “crazy paving” patterns, as they fill with mucus making it harder and harder to breathe.
“An interesting pattern is emerging in reports from China”, said Azra Ghani, professor of infectious disease epidemiology at Imperial College, London. “After the first week of infection there is a tipping point - where some patients go downhill but others remain more stable and then recover.”
What kills patients with coronavirus?
Patients die of a number of different causes depending on their general health. But what sparks the final decline in many patients is their own immune system going into overdrive as pneumonia develops.
This can trigger a “cytokine storm” where overproduction of immune cells further damages the lungs. This is the body’s inflammatory response to microbial infection and it can lead to organ failure and death. It was a common cause of death in the Spanish Flu of 1918. Older people with underlying conditions are more vulnerable but the young are not immune.
“What’s different with this disease is that it’s a new virus and therefore the whole population is potentially susceptible. Everyone is immunologically naive and no one has been exposed to it before,” said Prof Ghani.
How are people with coronavirus treated?
There is no simple cure for the new coronavirus – just as there is no cure for the common cold.
In the vast majority of cases, the disease is only mild and symptoms such as fever and general discomfort can be treated with aspirin and ibuprofen or packaged cold and flu remedies containing the same.
It is in more severe cases where pneumonia develops that the danger lies. Viral pneumonia cannot be treated with antibiotics and, for the moment at least, there are no antivirals specific to this particular virus.
Instead doctors focus on supporting patients' lung function as best they can.They may be given oxygen or placed on a breathing machine (ventilator) in the most severe cases.
Doctors in around the world with coronavirus patients are also testing and experimenting with new treatments, including drugs designed to combat HIV and other viral infections.
As more information on these treatments become available we will update readers here.
How many people might need hospital treatment?
It is not just the overall death rates that doctors are worried about. The number of people requiring hospital treatment is also vital to know as this determines the availability of hospital beds.
In China a study of the first 44,000 cases produced by the country’s health authority found that nearly 14 per cent were “severe”, requiring hospital treatment. A further five per cent were “critical” - that is, they had respiratory failure, septic shock and/or multiple organ failure and required intensive care.
Another related issue is the duration of the disease. According to one study in China of hospitalised patients who recovered, their pneumonia took a full 10 days to peak. This suggests demand on hospital beds will be high - hence the rapid construction of new hospitals in China.
The average hospital stay in China for Covid-19 patients is between 11 and 26 days. But the recovery period can be long - up to six weeks for some of the most severe patients.
Do coronavirus patients ever fully recover?
For the vast majority of people with mild disease, recovery is quick and there will be no lasting problems. They also develop some immunity to this strain of the virus.
However, for those who develop severe pneumonia there can be lasting lung damage. It is too early to say what the long-term prognosis is for these people, but some of the patients who recovered from Sars did suffer long-term health effects.
Will the NHS be able to cope if the virus gets a grip here?
This is another big unanswered question. If an outbreak in the UK can be delayed until the spring it would avoid the worst of the NHS winter pressures.
The latest data from the NHS show that in the week ending February 16 average bed occupancy in the 132 NHS trusts in England was at 94 per cent, with several hospitals reporting that they were at 100 per cent occupancy - that is, they had no free beds.
Read more: How would Britain cope with a pandemic?
The ideal, say planners, is for hospitals to run at about 85 per cent occupancy to ensure there is enough slack in the system in case of a sudden surge in demand.
If a China-style outbreak were to occur, the NHS would struggle to cope, says Jonathan Ball, professor of molecular virology at the University of Nottingham. “We know what happens with seasonal flu – the NHS cannot cope very well. So this could put further pressure on services,” he said.
The government is more optimistic. "The NHS is extremely well prepared and used to managing infections,” said a number 10 spokesman.
Can the coronavirus be stopped?
It is looking less likely the virus can be stopped from becoming a pandemic and working its way around the world.
Currently, the WHO and British government are still focusing on containing the disease but expect them to shift to a strategy of “mitigation” if this does not work.
Mitigation follows containment in the public health response to all major infectious disease outbreaks. They can be run in tandem but while containment strategies aim to stop or hold back a disease, the goal of mitigation is to reduce its impact on society.
“The ultimate goal of [mitigation] measures is to reduce the intensity of an outbreak, flattening out the epidemic curve and therefore reducing strain on the health system, and on social economic well-being,” says Dr Josh Michaud, an associate director for global health policy at the Kaiser Family Foundation.
In simple terms planners will try to prevent sharp spikes in case numbers so the NHS and other services do not become overwhelmed.
What will mitigation look like in Britain?
Mitigation efforts in the UK will be driven by the UK Influenza Pandemic Preparedness Strategy 2011 and fall into four main areas:
Encouraging individual behaviour change - hand washing, staying at home if unwell, looking out for neighbours and relatives.
Social distancing - encouragement of home working, discouraging public gatherings, possible school closures, international travel restrictions, online medical consultation and testing
Environmental hygiene - cleaning and spraying public surfaces, stepping up checks on restaurants and takeaways, ensuring good funeral practices
Building medical capacity - stockpiling of protective equipment and drugs, limiting non-essential hospital visits and operations, developing effective treatments and vaccines
What about quarantines?
Quarantines are about containment but expect to see such strategies run alongside mitigation measures if health authorities think it will buy more time.
Italy, for instance, has followed China’s example and placed more than 50,000 people under quarantine in a series of villages in the north of the country.
The recently updated Public Health (Control of Disease) Act 1984 affords the government similar powers here but whether they will be used is a moot point and is likely to hinge on the exact circumstances.
The Prime Minister's official spokesman knocked the ball into the Department of Health’s court on Monday saying: "We will be led by the advice from public health and medical experts and will take steps which they feel are required to best protect the British public."
Public health officials would have to balance the impact on people’s freedom with the wider impact on public health. They must also get approval from a local justice of the peace.
While it is conceivable that quarantines could be placed on containable communities should an outbreak occur, large scale quarantines or curfews seem unlikely unless the severity of the virus takes a turn for the worse. Any action would have to be judged proportionate.