- severe
lung disease
- virus
- 4,500
confirmed cases
- patients
with pneumonia
- outbreak
be contained
- caused
- Severe
acute respiratory syndrome (Sars),
- Infected
- Symptoms
- Spread
- Epidemic
- global
pandemic like swine flu
- epidemic
- Vaccine
A virus - previously unknown to science - is
causing severe lung disease in China and has also been detected in other
countries.
More than 100 people are known to have died
from the virus, which appeared in the Chinese city of Wuhan in December.
There are already more than 4,500 confirmed
cases, and experts expect the number will keep rising.
A new virus arriving on the scene, leaving
patients with pneumonia, is always a worry and health officials around the
world are on high alert.
Can this outbreak be contained or is this
something far more dangerous?
What
is this virus?
Officials in China have confirmed the cases
are caused by a coronavirus.
These are a broad family of viruses, but only six (the
new one would make it seven) are known to infect people.
Severe acute respiratory syndrome (Sars),
which is caused by a coronavirus, killed 774 of the 8,098 people infected in an
outbreak that started in China in 2002.
"There is a strong memory of Sars, that's
where a lot of fear comes from, but we're a lot more prepared to deal with
those types of diseases," says Dr Josie Golding, from the Wellcome Trust.
How
severe are the symptoms?
It seems to start with a fever, followed by a
dry cough and then, after a week, leads to shortness of breath and some
patients needing hospital treatment.
Around one-in-four cases are thought to be
severe.
Notably, the infection rarely seems to cause a
runny nose or sneezing.
The coronavirus family itself can cause
symptoms ranging from a mild cold all the way through to death.
"When we see a new coronavirus, we want
to know how severe are the symptoms. This is more than cold-like symptoms and
that is a concern but it is not as severe as Sars," says Prof Mark
Woolhouse, from the University of Edinburgh.
The World Health Organization (WHO) says it is
an emergency in China, but decided not to declare an international public
health emergency - as it did with swine flu and Ebola.
How
deadly is it?
More than 100 people are known to have died
from the virus - but while the ratio of deaths to known cases appears low, the
figures are unreliable.
But the infection seems to take a while to
kill, so more of those patients may yet die.
And it is unclear how many unreported cases
there are.
Where
has it come from?
New viruses are detected all the time.
They jump from one species, where they went
unnoticed, into humans.
"If we think about outbreaks in the past,
if it is a new coronavirus, it will have come from an animal reservoir,"
says Prof Jonathan Ball, a virologist at the University of Nottingham.
Many of the early coronavirus cases were
linked to the South China Seafood Wholesale Market, in Wuhan.
But the earliest documented case, which has
been traced back to 1 December, had no connection to the market.
Sars started off in bats and then infected the
civet cat, which in turn passed it on to humans.
And Middle East respiratory syndrome (Mers), which has killed
858 out of the 2,494 recorded cases since it emerged in 2012,
regularly makes the jump from the dromedary camel.
Which
animal?
Once the animal reservoir (where the virus
normally camps out) is detected, then the problem becomes much easier to deal
with.
While some sea-going mammals can carry coronaviruses (such as the Beluga whale),
the South China Seafood Wholesale Market also has live wild animals, including
chickens, bats, rabbits, snakes, which are more likely to be the source.
Researchers say the new virus is closely
related to one found in Chinese horseshoe bats.
However, this does not mean wild bats are the
source of the outbreak - they could have passed the virus onto another species
sold at the market.
Why
China?
Prof Woolhouse says it is because of the size
and density of the population and close contact with animals harbouring
viruses.
"No-one is surprised the next outbreak is
in China or that part of the world," he says.
How
easily does it spread between people?
At the beginning of the outbreak, the Chinese
authorities said the virus was not spreading between people - but now, such
cases have been identified.
Scientists have now revealed each infected
person is passing the virus on to between 1.4 and 2.5 people.
This figure is called the virus' basic
reproduction number - anything higher than 1 means it's self-sustaining.
We now know this is not a virus that will burn
out on its own and disappear.
Only the decisions being made in China -
including shutting down cities - can stop it spreading.
While those figures are early estimates, they
put coronavirus in roughly the same league as Sars.
When
are people infectious?
Chinese scientists say people are infectious
even before their symptoms appear.
The time between infection and symptoms -
known as the incubation period - lasts between one and 14 days.
Sars and Ebola are contagious only when symptoms
appear. Such outbreaks are relatively easy to stop: identify and isolate people
who are sick and monitor anyone they came into contact with.
Flu, however, is the most famous example of a
virus that you spread before you even know you're ill.
Prof Wendy Barclay from the department of
infectious disease at Imperial College London said it was common for lung
infectious to spread without symptoms.
The virus is "carried into the air during
normal breathing and talking by the infected person," she explained.
"It would not be too surprising if the
new coronavirus also does this."
We are not at the stage where people are
saying this could be a global pandemic like swine flu.
But the problems of stopping such
"symptomless spreaders" will make the job of the Chinese authorities
much harder.
What is not known is how infectious people are
during the incubation period.
How
fast is it spreading?
It might appear as though cases have soared.
But this is somewhat misleading.
Many of these seeming new cases will have come
to light as a result of China improving its ability to find infected people.
There is actually very little information on
the "growth rate" of the outbreak.
But experts say the number of people becoming
sick is likely to be far higher than the reported figures.
A report last week by the MRC Centre for
Global Infectious Disease Analysis at Imperial College London said: "It is
likely that the Wuhan outbreak of a novel coronavirus has caused substantially
more cases of moderate or severe respiratory illness than currently
reported."
And over the weekend, researchers at Lancaster
University estimated the number of cases suggesting 11,000 have been infected
this year. If true, that would be more than Sars.
Could
the virus mutate?
Yes, you would expect viruses to mutate and
evolve all the time. But what this means is harder to tell.
China's National Health Commission has warned
the coronavirus's transmission ability is getting stronger, but they were
unclear on the risks posed by mutations of the virus.
This is something scientists will be watching
closely.
How
can the virus be stopped?
We now know the virus will not stop on its own;
only the actions of the Chinese authorities can bring this epidemic to an end.
There is also no vaccine to give people
immunity to the virus.
The only option is to prevent people who have
become infected from spreading the virus to others.
That means:
§ Limiting
people's movement
§ Encouraging
hand-washing
§ Treating
patients in isolation with healthcare workers wearing protective gear
A massive feat of detective work will also be
needed to identify people whom patients have come into contact with to see if
they have the virus.
Scientists in China have been using medication
that they hope may help coronavirus patients in their recovery. It is too soon
to say whether the two antiviral drugs (lopinavir and ritonavir) either
together or in combination with other agents will work. They were also used by
doctors during the Sars and Mers outbreaks.
How
have Chinese authorities responded so far?
China has done something unprecedented
anywhere in the world - by effectively putting Wuhan into
quarantine.
Travel restrictions have also been imposed on
a dozen other cities with 36 million people affected.
Some mass gatherings have been banned and
tourists sites, including part of the Great Wall, have been closed.
And a ban on the sale of wildlife, a possible source
of the infection, has been imposed.
Wuhan - the centre of the outbreak - is
building a two new hospitals with beds for a total of 2,300 people.
How
is the world responding?
Most Asian countries have stepped up
screenings of travellers from Wuhan and the WHO has warned hospitals worldwide
a wider outbreak is possible.
Singapore and Hong Kong have been screening
air passengers from Wuhan and authorities in the US and the UK have announced
similar measures.
However, questions remain about the effectiveness
of such measures.
If it takes up to two weeks for symptoms to
appear, then someone could easily be halfway round the world and have passed
through any screening checks before starting to feel ill.
How
worried are the experts?
Dr Golding says: "At the moment, until we
have more information, it's really hard to know how worried we should be.
"Until we have confirmation of the
source, that's always going to make us uneasy."
Prof Ball says: "We should be worried
about any virus that explores humans for the first time, because it's overcome
the first major barrier.
"Once inside a [human] cell and
replicating, it can start to generate mutations that could allow it to spread
more efficiently and become more dangerous.
"You don't want to give the virus the
opportunity."
Are
there any vaccines or treatments?
No.
However, the work to develop them is already
under way. It is hoped that research into developing a vaccine for Mers, which
is also a coronavirus, will make this an easier job.
And hospitals are testing anti-viral drugs to
see if they have an impact.
A combination of two drugs - lopinavir and
ritonavir - was successful in the Sars epidemic and are being tested in China.
