Just three months ago, few people even knew the word “coronavirus”. But as the disease continues to spread across the globe, infecting and killing thousands, and causing millions to live in self-isolation, it has become a watchword for the daily life of billions. Here are some of the questions that have been raised since coronavirus became headline news around the world: Who is most at risk? The severity of COVID-19, the disease caused by the new coronavirus, increases with age, as various studies have shown. Published on March 31, the latest edition of the British medical journal “The Lancet” shows that the disease is on average much more dangerous for those over 60, with a mortality rate of 6.4 percent (among confirmed cases). The mortality rate climbs to 13.4 percent for the over 80s against just 0.32 percent of deaths for the under 60s, according to studies made mainly on several hundred Chinese cases observed in February. Similarly, the study shows that the proportion of patients requiring hospitalisation increases sharply with age: 0.04 percent for 10 to 19-year-olds, 4.3 percent for 40 to 49-year-olds, 11.8 percent for 60 to 69, and 18.4 percent for those over 80. The last of these figures means that about one in five octogenarians develops a form serious enough to require hospitalisation. Besides age, having a chronic illness — for example, respiratory failure, heart disease, history of stroke, cancer — is also a risk factor. In a recent report on 10,000 deaths, the Italian Higher Institute of Health (ISS) identified common existing illnesses in the deceased. The most common are hypertension (73.5 percent of cases), diabetes (31 percent) and coronary heart disease (27 percent). Finally, according to an extensive analysis published on February 24 by Chinese researchers in the American medical journal “Jama”, the disease is mild in 80.9 percent of cases, “serious” in 13.8 percent of cases and “critical” in 4.7 percent of cases. How many deaths can we expect? The statistical correlation between the number of deaths in the world and the total number of officially registered cases, suggests COVID-19 kills approximately five percent of diagnosed patients, with disparities according to different countries. But that fatality rate has to be treated with caution as it is unclear how many people have actually been infected. Since many patients seem to develop few or no symptoms, their number is likely to be greater than the cases detected, which would therefore lower this rate. In addition, countries have very different testing policies and some do not systematically test all suspected cases. A few weeks ago Anthony Fauci, director of the National Institute of Infectious Diseases in the US, told Congress that the fatality rate was much lower than five percent. “If you count all the cases of minimally symptomatic or asymptomatic infections, that probably brings the mortality rates down to somewhere around one percent,” he said, adding that this still makes coronavirus “10 times more lethal than the seasonal flu”. The study published in “The Lancet” on March 31 estimated the proportion of deaths among the confirmed cases at 1.38 percent. However, the danger of a disease does not only depend on the overall death rate but also on its ability to spread. Even if only one percent of patients die, “it can make significant figures if 30 percent or 60 percent of a population is infected,” said Simon Cauchemez, of the Pasteur Institute in Paris. The other factor that is affecting the fatality rate of this new disease is the congestion of hospitals, caused by a sudden and a massive influx of cases. This complicates matters not only for those patients with severe forms of COVID-19 but for everyone else as well. What are the symptoms? According to the World Health Organization (WHO), the most common symptoms “include respiratory problems, fever, cough, shortness of breath and difficulty breathing”. Each of these symptoms may be present to a greater or lesser extent depending on the case, and the development of symptoms fluctuates. Another common symptom is loss of smell and taste. According to a recent Belgian study carried out on 417 patients who were “non-severely” infected, 86 percent had problems with smell — most of them no longer sensing anything — and 88 percent had taste disorders. Symptoms usually last two weeks or more, sometimes less. For some people it will get worse. “In the most severe cases, the infection can lead to pneumonia, severe acute respiratory syndrome, kidney failure, and even death,” says the WHO. There is no vaccine or medication, and managing the virus involves treating the symptoms. However, some patients are administered antiviral drugs or other experimental treatments, the effectiveness of which is still being evaluated.