A new virus that was first reported in the central city of Wuhan is spreading from person to person and has infected health workers. The previously unknown coronavirus infected people across China and spread to almost every continent. The World Health Organisation (WHO) has declared the spread of the Covid-19 disease caused by the coronavirus outbreak as a pandemic. Here is what we know so far: What is a coronavirus? Medical experts in China identified the virus as a new strain of coronavirus, later named SARS-CoV-2, in early January. Coronaviruses are a large family of viruses causing illnesses ranging from the common cold to more severe diseases such as Middle East respiratory syndrome (Mers) and severe acute respiratory syndrome (Sars), according to the World Health Organisation (WHO). Coronaviruses commonly circulate in animals, but some can evolve to infect humans and spread between people. Only seven, including the new virus, are known to infect people, according to the US Centres for Disease Control and Prevention (CDC). There are no specific treatments such as vaccines for the coronavirus but many symptoms caused by the virus can be treated. What are the symptoms? The most common symptoms of Covid-19 according to WHO are: Fever Tiredness Dry cough In April, the CDC released six additional symptoms, including chills, muscle pain and sore throat, which may appear two to 14 days after exposure to the virus. The symptoms of Covid-19 according to the CDC are: Fever Shortness of breath Dry cough Chills Repeated shaking with chills Muscle pain Headache Sore throat New loss of taste or smell What has the WHO said? The WHO initially declared a global public health emergency , citing the potential of the virus to spread to countries not prepared to deal with the contagion. It later said the spread of the coronavirus was a pandemic . The term is used when a disease has spread to several countries or continents, usually affecting a large number of people. It did not recommend restrictions on travel to or trade with China. Many countries in Asia have imposed lockdowns and travel restrictions on its residents. Why is there such a concern? The virus has caused alarm because of its resemblance to Sars, which infected more than 8,000 people globally and killed over 600 in mainland China and Hong Kong in 2002-03. The global death toll has since surpassed that of Sars . Zhong Nanshan, a leading expert on communicable diseases in China and on the Sars virus, confirmed human-to-human transmission . He also said the infection of medical personnel was alarming and warned of the risk of super-spreaders. So-called super-spreaders are people at the most virulent stage of infection who are more likely to spread the disease to others. Scientists have found traces of the virus in the faeces of some infected patients , possibly indicating an additional mode of transmitting the disease. What preventive measures can be taken? To prevent the spread of the virus, the WHO recommends washing hands regularly, covering the mouth and nose when coughing and sneezing, and thoroughly cooking meat and eggs. It also suggests avoiding close contact with anyone showing symptoms of respiratory illness. Maria Van Kerkhove, of the WHO’s emerging disease and zoonoses unit, recommends avoiding unnecessary unprotected contact with live animals, and thorough hand washing after contact with an animal. Gabriel Leung, co-director of the University of Hong Kong’s WHO Collaborating Centre for Infectious Disease Epidemiology and Control, said masks should be part of preventive efforts. “If you are ill, put on a mask. If you are going to a crowded place, put on a mask even if you are not ill,” Leung said. “If you have any symptoms, especially if you have travelled to Wuhan, please seek medical attention and be honest and open with your doctors.” How does coronavirus testing work and how can you get tested? The coronavirus testing process depends on the instructions of the health authorities of the place where you live. In Hong Kong, it is recommended people call their doctors and get tested if they have symptoms of infection, they have travelled to regions with high infection rates, or they have had close contacts with someone infected. Two types of tests are done in Hong Kong – an antigen test and an antibody test. While the antigen test detects the presence of the Sars-Cov-2 in your body, the antibody test detects your immunity response to the virus – if you were infected earlier, you would have developed antibodies to it. Tests are available at government general outpatient clinics and some private clinics . Hong Kong doctors normally recommend a PCR test to get more accurate results, although it takes more time – a few hours – than a blood test, which only takes a few minutes. Coronavirus testing: how it works and where to get tested for Covid-19 Is there a cure or vaccine? There is still no approved antiviral or specific SARS-CoV-2 vaccine . However, a number of proposed antiviral treatments and vaccines for Covid-19 are currently in the experimental phase, just months after the coronavirus was identified. Many of the proposals now under study come from research groups that have spent years working to combat similar coronaviruses, particularly severe acute respiratory syndrome (Sars) and Middle East respiratory syndrome (Mers). All that accumulated knowledge has allowed scientists to advance at unprecedented speed. The race is on in the drug battle against the coronavirus Antiviral treatments Antivirals are drugs that interfere with the replication of harmful viruses without also harming the host cells. One of the most promising antiviral treatments for SARS-CoV-2 is called remdesivir , which has been used successfully against Sars, Mers and Ebola. At least 13 clinical trials are already under way in China and the United States to see if remdesivir may stop SARS-CoV-2. Coronavirus vaccines The World Health Organisation highlights at least 41 proposed vaccines for testing against coronavirus. Vaccines are a prevention strategy. If they are developed now, they can give people immunity from future outbreaks. One of the most advanced efforts is happening in China with a recombinant adenovirus vector-based vaccine based on the SARS-CoV-2 S gene. When tested in monkeys, this vaccine candidate produced antibodies, which help fight the virus. A phase I clinical trial will soon begin in Wuhan with 108 healthy volunteers between 18 and 60 years old, in which three different doses will be tested. Additional reporting by Elizabeth Cheung Foreign nationals living in China can find further information and advice about the virus here .