Here are five key questions that remain unanswered about the virus officially known as SARS-CoV-2 that leads to Covid-19.
1. Does it hang in the air?
Coronavirus is known to spread through physical contact and through droplets dispersed when an infected person coughs or sneezes. But can it also hang in the air like the virus that causes the seasonal flu?
One US study published in the New England Journal of Medicine shows that the new coronavirus can survive in air particles in a laboratory for three hours. But scientists do not know if the disease can still be transmitted at that stage. [Read: 5 Mistake you are making when wearing coronavirus facemask]
2. How many people have got it?
Apart from the few countries that have used aggressive testing, like South Korea and Germany, global figures on the number of people carrying the virus are sketchy.
The British government estimated that on 17 March, 55,000 people there had the virus when less than 2,000 had officially tested positive.
A precise understanding of the spread of the epidemic is vital to isolating and treating those infected as well as developing a profile of those who can build up immunity to it.
This will be possible once a new generation of blood tests are developed that are capable of tracing the immune reaction to SARS-CoV-2. [Read: 7 Practiced tips for dating during these coronavirus pandemic]
3. Will good weather kill it?
Will Covid-19 be halted with the arrival of warm spring and summer weather in the northern hemisphere? Experts say this is possible, but not sure.
Respiratory viruses like the flu are more stable in cold and dry weather, which is why they spread more rapidly in winter.
But a recent study by the Harvard Medical School in the United States warned that “changes in weather alone (with an increase of temperature and humidity as spring and summer months arrive in the northern hemisphere) will not necessarily lead to declines in Covid-19 cases without the implementation of extensive public health interventions”. [Read: How to protect yourself from coronavirus]
4. Why are children not severely hit?
Covid-19 has relatively spared children than adults, and those infected have been less sick.
Chinese research published in the review Nature showed that none of the ten children with Covid-19 they followed became terribly ill, with symptoms limited to sore throats, a cough, and a mild fever.
Researchers also found that children living with people sick with the virus were two to three times less likely to catch it than adults. The same was true of the SARS virus in 2002-03.
“There are lots of things that we do not know, which should lead us to approach this with a lot of humility,” warned Professor Lacombe. [Read: how to get rid of coronavirus anxiety(fear)}
5. Why is it serious for only some?
One of the biggest mysteries is why the virus produces few or no symptoms in around 80% of people, according to the World Health Organisation, yet in others, it can lead to fatal pneumonia.
“Findings from February indicated that the clinical spectrum of this disease could be very heterogeneous,” said Professor Leo Poon from the School of Public Health at Hong Kong University.
During the peak of the epidemic in China, he and a team from the University of Nanchang compared those with mild and severe forms of the illness.
Their study, published in the British journal The Lancet, found that those hardest hit were “significantly older” and that the concentration of the virus in the nose and throat was around 60 times higher than those lightly affected.
The question remains whether this result can be explained by the subjects’ less reactive immune systems because of their age or whether they were simply more exposed to the virus.
Research on the measles virus has shown that the gravity of the illness is related to the level of exposure. Experts do not yet know whether this is the same for Covid-19.