Wearing a mask and maintaining physical distance from others is important even when none of you are showing symptoms of COVID-19, experts say.
This is partly due to the risk of transmission by asymptomatic people — those who have the novel coronavirus, but aren’t showing any symptoms.
This is playing a role in the spread of COVID-19, the World Health Organization said Tuesday, clarifying some remarks they made just a day before suggesting that it only made a small difference.
“Some estimates of around 40 percent of transmission may be due to asymptomatic (cases), but those are from models. So I didn’t include that in my answer yesterday but wanted to make sure that I made that clear,” said Dr. Maria van Kerkhove, a WHO epidemiologist and technical lead on the pandemic.
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Here’s what we know, and don’t know, about the phenomenon so far.
What is asymptomatic transmission?
Dr. Isaac Bogoch, an infectious diseases specialist at Toronto General Hospital, believes it’s important to draw distinctions between three categories of patients.
These are asymptomatic patients, who have the disease but never show any signs of it, “pre-symptomatic” patients, who are infected but haven’t yet developed a cough, fever or other symptoms, and “Pauci-symptomatic” patients, who show only extremely mild symptoms.
These are sometimes grouped together in the medical literature, he said, which can be a little confusing.
3:37 Coronavirus outbreak: WHO ‘absolutely convinced’ that asymptomatic transmission is occurring
Coronavirus outbreak: WHO ‘absolutely convinced’ that asymptomatic transmission is occurring
The World Health Organization believes that pre-symptomatic transmission — passing along the virus before you have symptoms — is a big deal.
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“It appears from very limited information we have right now that people have more virus in their body at or around the time that they develop symptoms, so very early on,” van Kerkhove said.
The other types, however, do exist. A recent study from Vietnam documented true asymptomatic cases of COVID-19, Bogoch noted. After following some people who had tested positive for nearly a month, many still didn’t show any symptoms.
This is one of the big unanswered questions, according to van Kerkhove, though there are estimates.
“We know that probably around 30 per cent of people that get COVID are probably asymptomatic or they have very minimal in the way of symptoms, not the typical cough and fever,” said Dr. Sumon Chakrabarti, an infectious diseases specialist at Trillium Health Partners in Mississauga, Ont.
The research is a bit all over the place though, according to the WHO, which notes that one systematic review found that the proportion of asymptomatic cases ranged from six to 41 per cent, depending on the study.
How much do they spread the virus?
“We know that asymptomatic people can for sure transmit the virus and in fact it might be one of the reasons it was so successful at the beginning of the pandemic,” said Dr. Matthew Pellan Cheng, a clinician scientist at the McGill University Health Centre, who is also on the federal government’s COVID-19 Immunity Task Force.
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How much disease transmission asymptomatic people account for might depend a lot on local conditions, he said.
“If you’re in a situation in a community where there’s tons of symptomatic individuals, then the relative contribution to transmission of asymptomatic people is probably less. But at the onset of a pandemic when very few people are infected, then they probably actually contribute relatively more than symptomatic people.”
Chakrabarti believes that asymptomatic transmission is probably less important than symptomatic transmission, but that it remains a factor in the pandemic.
“It probably does play a role. And it’s one that is very important to be wary of, because if we don’t account for that, then we can actually have ongoing transmission and not know it,” he said.
Dr. Mike Ryan, the WHO’s top emergencies expert, said that people might be at their most contagious before they actually show symptoms.
The novel coronavirus lodges in the upper respiratory tract, he said, making it easier to transmit by droplets than related viruses such as SARS or MERS, which are in the lower tract.
3:51 Is it COVID-19 or just seasonal allergies?
Is it COVID-19 or just seasonal allergies?
“Now as we look at COVID-19, we have an infectious pathogen that is present in the upper airway for which the viral loads are peaking at the time you are just beginning to get sick,” he said.
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“That means you could be in the restaurant feeling perfectly well and start to get a fever, you are feeling ok, you didn’t think to stay home, but that’s the moment at which your viral load could be actually quite high,” he said.
Ryan added: “And it’s because the disease can spread at that moment that the disease is so contagious. That’s why it spread around the world in such an uncontained way, is because it’s hard to stop this virus.”
How should this affect our behaviour?
We have to take precautions against asymptomatic or pre-symptomatic transmission, the experts say.
“Because this virus is known to transmit even in the absence of symptoms, you need to be on high alert pretty much all the time,” Cheng said.
That means keeping your distance from others, avoiding crowded places, and wearing a mask when you have to be close, he said.
“You can’t trust yourself not to transmit to other people.”
“Just because you don’t have any symptoms does not mean that the next person will also be asymptomatic.”
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Bogoch believes that even people who only have mild symptoms, like a cough, should still get tested, so that if they do have the disease, they can take appropriate isolation measures.
“With public education and with ensuring access to diagnostic testing, we can probably more readily identify people with mild symptoms in the community,” he said. “And we can further prevent community transmission.”
Questions about COVID-19? Here are some things you need to know:
Symptoms can include fever, cough and difficulty breathing — very similar to a cold or flu. Some people can develop a more severe illness. People most at risk of this include older adults and people with severe chronic medical conditions like heart, lung or kidney disease. If you develop symptoms, contact public health authorities.
To prevent the virus from spreading, experts recommend frequent handwashing and coughing into your sleeve. They also recommend minimizing contact with others, staying home as much as possible and maintaining a distance of two metres from other people if you go out. In situations where you can’t keep a safe distance from others, public health officials recommend the use of a non-medical face mask or covering to prevent spreading the respiratory droplets that can carry the virus.
For full COVID-19 coverage from Global News, click here.
VANCOUVER – Mayors and other leaders from several British Columbia communities say the provincial and federal governments need to take “immediate action” to tackle mental health and public safety issues that have reached crisis levels.
Vancouver Mayor Ken Sim says it’s become “abundantly clear” that mental health and addiction issues and public safety have caused crises that are “gripping” Vancouver, and he and other politicians, First Nations leaders and law enforcement officials are pleading for federal and provincial help.
In a letter to Prime Minister Justin Trudeau and Premier David Eby, mayors say there are “three critical fronts” that require action including “mandatory care” for people with severe mental health and addiction issues.
The letter says senior governments also need to bring in “meaningful bail reform” for repeat offenders, and the federal government must improve policing at Metro Vancouver ports to stop illicit drugs from coming in and stolen vehicles from being exported.
Sim says the “current system” has failed British Columbians, and the number of people dealing with severe mental health and addiction issues due to lack of proper care has “reached a critical point.”
Vancouver Police Chief Adam Palmer says repeat violent offenders are too often released on bail due to a “revolving door of justice,” and a new approach is needed to deal with mentally ill people who “pose a serious and immediate danger to themselves and others.”
This report by The Canadian Press was first published Sept. 16, 2024
The Canadian government says it will donate up to 200,000 vaccine doses to fight the mpox outbreak in Congo and other African countries.
It says the donated doses of Imvamune will come from Canada’s existing supply and will not affect the country’s preparedness for mpox cases in this country.
Minister of Health Mark Holland says the donation “will help to protect those in the most affected regions of Africa and will help prevent further spread of the virus.”
Dr. Madhukar Pai, Canada research chair in epidemiology and global health, says although the donation is welcome, it is a very small portion of the estimated 10 million vaccine doses needed to control the outbreak.
Vaccine donations from wealthier countries have only recently started arriving in Africa, almost a month after the World Health Organization declared the mpox outbreak a public health emergency of international concern.
A few days after the declaration in August, Global Affairs Canada announced a contribution of $1 million for mpox surveillance, diagnostic tools, research and community awareness in Africa.
On Thursday, the Africa Centres for Disease Control and Prevention said mpox is still on the rise and that testing rates are “insufficient” across the continent.
Jason Kindrachuk, Canada research chair in emerging viruses at the University of Manitoba, said donating vaccines, in addition to supporting surveillance and diagnostic tests, is “massively important.”
But Kindrachuk, who has worked on the ground in Congo during the epidemic, also said that the international response to the mpox outbreak is “better late than never (but) better never late.”
“It would have been fantastic for us globally to not be in this position by having provided doses a much, much longer time prior than when we are,” he said, noting that the outbreak of clade I mpox in Congo started in early 2023.
Clade II mpox, endemic in regions of West Africa, came to the world’s attention even earlier — in 2022 — as that strain of virus spread to other countries, including Canada.
Two doses are recommended for mpox vaccination, so the donation may only benefit 100,000 people, Pai said.
Pai questioned whether Canada is contributing enough, as the federal government hasn’t said what percentage of its mpox vaccine stockpile it is donating.
“Small donations are simply not going to help end this crisis. We need to show greater solidarity and support,” he said in an email.
“That is the biggest lesson from the COVID-19 pandemic — our collective safety is tied with that of other nations.”
This report by The Canadian Press was first published Sept. 13, 2024.
Canadian Press health coverage receives support through a partnership with the Canadian Medical Association. CP is solely responsible for this content.
HALIFAX – The Nova Scotia government says it could be months before it reveals how many people are on the wait-list for a family doctor.
The head of the province’s health authority told reporters Wednesday that the government won’t release updated data until the 160,000 people who were on the wait-list in June are contacted to verify whether they still need primary care.
Karen Oldfield said Nova Scotia Health is working on validating the primary care wait-list data before posting new numbers, and that work may take a matter of months. The most recent public wait-list figures are from June 1, when 160,234 people, or about 16 per cent of the population, were on it.
“It’s going to take time to make 160,000 calls,” Oldfield said. “We are not talking weeks, we are talking months.”
The interim CEO and president of Nova Scotia Health said people on the list are being asked where they live, whether they still need a family doctor, and to give an update on their health.
A spokesperson with the province’s Health Department says the government and its health authority are “working hard” to turn the wait-list registry into a useful tool, adding that the data will be shared once it is validated.
Nova Scotia’s NDP are calling on Premier Tim Houston to immediately release statistics on how many people are looking for a family doctor. On Tuesday, the NDP introduced a bill that would require the health minister to make the number public every month.
“It is unacceptable for the list to be more than three months out of date,” NDP Leader Claudia Chender said Tuesday.
Chender said releasing this data regularly is vital so Nova Scotians can track the government’s progress on its main 2021 campaign promise: fixing health care.
The number of people in need of a family doctor has more than doubled between the 2021 summer election campaign and June 2024. Since September 2021 about 300 doctors have been added to the provincial health system, the Health Department said.
“We’ll know if Tim Houston is keeping his 2021 election promise to fix health care when Nova Scotians are attached to primary care,” Chender said.
This report by The Canadian Press was first published Sept. 11, 2024.
