There are two key unanswered questions surrounding the novel coronavirus: How easily can it be transmitted between people? And how dangerous is it? The next month in the outbreak could be critical in revealing clues to better answer those questions, infectious disease experts say.
In Canada, officials have confirmed a case in Ontario, a presumptive case related to the first and a presumptive illness in British Columbia.
Health officials in Canada and the U.S. stress that while human-to-human transmission of the virus has occurred, it is most likely when someone is in close, prolonged contact with a person who is infected. Chinese health authorities said Tuesday that the new coronavirus has infected more than 4,500 people in China, including 106 who've died.
In Germany, Vietnam, Taiwan and Japan, the virus has spread person-to-person, rather than from a traveller arriving from China, heightening concerns the virus might transmit more easily than thought.
The virus has also spread to several other countries.
Dr. Tedros Adhanom Ghebreyesus, the director-general of the World Health Organization, met Chinese President Xi Jinping in Beijing on Tuesday to share information on the outbreak.
"Both WHO and China noted that the number of cases being reported, including those outside China, is deeply concerning," the United Nations health agency said in statement on Tuesday. "Better understanding of the transmissibility and severity of the virus is urgently required to guide other countries on appropriate response measures." Early information during an outbreak should be viewed with caution because it is often based on the worst cases involving patients who die or need intensive care or hospitalization. But how many people lack symptoms or aren't sick enough to seek medical care isn't known, so the full picture of the illness, such as the extent of mild cases, isn't yet clear. Dr. Michael Gardam, an infectious disease physician and chief of staff at Humber River Hospital in Toronto, said before symptoms start, the risk of someone spreading infectious particles is thought to be small. "When they have symptoms they are also coughing and spraying the virus out," Gardam said.
Dr. Anthony Fauci, director of the U.S. National Institute of Allergy and Infectious Diseases, told reporters that spread of the virus when people don't have symptoms is rare.
"In all the history of respiratory-borne viruses of any type, asymptomatic transmission has never been the driver of outbreaks," Fauci said in Washington. "The driver of outbreaks is always a symptomatic person."
Dr. Bonnie Henry, a provincial health officer for British Columbia who was an associate medical officer of health in Toronto during the 2002/03 SARS outbreak, said we are in a "critical period right now" for dealing with this new coronavirus. How the outbreak unfolds in the next month will shed light on whether the virus transmits easily between people or could be stamped out, Henry said.
"The world needs to be in full containment mode."
Henry said the public health response focuses on:
- Detecting infected people early.
- Isolating them appropriately.
- Providing medical care for patients.
Those containment measures aim to slow the geographic spread of the virus as well as the number of people who become infected and die.
On Monday, federal public health officials announced they're stepping up staffing at airports in Toronto, Montreal and Vancouver to support border officials in screening passengers arriving from China for symptoms. While the specifics of how well this new coronavirus transmits between people and its lethality aren't yet known, scientists are working under the assumption that like other respiratory cornaviruses, including SARS, the new virus spreads in droplets.
"When somebody coughs or sneezes and they breathe them in, we know that people get infected with the virus deep into the lung. We have receptors for these coronaviruses deep into the lungs," Henry said. In contrast, the measles virus is highly contagious and it can be transmitted through small droplets in the air that can last for hours. "This is not what we see with coronaviruses. Somebody has to be in the same air space usually within a maximum of two metres," Henry said. Canadian health officials want to offer guidance to airline passengers who sat within two metres or about three rows of the person with the first confirmed case in Canada and his wife. They took a flight on Jan. 21 from Wuhan to Guangzhou, then from Guangzhou to Toronto, arriving on Jan. 22. They were masked during the flight. While it's not clear how long the coronavirus can survive on hard surfaces, infectious disease experts consider simply walking past an ill passenger on a plane to be a low-risk situation.
Dr. Barbara Yaffe, Ontario's associate chief medical officer of health, said to be tested, people need to meet two criteria:
- Have respiratory symptoms like fever and cough.
- Have travelled to Wuhan or the surrounding areas within the past 14 days.
Canada's chief public health officer, Dr. Theresa Tam, said the risk to the general Canadian population from coronavirus remains low but more cases are expected.
Tam said health officials will be looking at epidemiology or population health data to determine if travel advisories will be expanded beyond the affected regions in China. Health officials say the best ways to protect against all respiratory infections are to get an annual flu shot, wash your hands, try not to touch your face or mouth, cover coughs or sneezes and stay home when sick.