How COVID-19 'silent spreaders' walk among us and can make an outbreak explode - Brantford Expositor | Canada News Media
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How COVID-19 'silent spreaders' walk among us and can make an outbreak explode – Brantford Expositor

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Studies show ‘undocumented’ cases, where people experience little to no symptoms, are doing untold damage

In the early days of the COVID-19 pandemic, public health officials were confident that it was “rare” for people not experiencing flu-like symptoms to pass the virus on to another person.

But according to a new study published in the Science journal that tracked and simulated the outbreak of the novel coronavirus in mainland China, nine of 10 infections were transmitted locally by people who were asymptomatic and, for all intents and purposes, healthy.

The analysis found that these “undocumented” carriers, with symptoms that were either mild or non-existent, were able to bypass any type of virus report. At the same time, they were still half as likely to spread it to someone else, the L.A. Times reported. And there were far more of them, meaning the infections they caused dwarfed other methods of spread.

They were the silent spreaders.

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In China, where the number of locally transmitted cases exploded in a short period of time, their effect was much greater than previously realized. In the earliest days of the outbreak in mainland China — Jan. 10 and Jan. 23 — people who were not hospitalized were the most likely carriers of the virus.

The Columbia University infectious diseases researcher and study lead for the new report, Jeffrey Shaman, called this phenomenon “stealth transmission” and said it was a “major driver” of the spread of COVID-19.

He added that this mode of transmission has remained “substantially undetected, and it’s flying below the radar.”

Shaman’s study simulated a transmission landscape that represented 375 cities in China and used available Chinese social media data to map the effects of at least 173 billion “travel events” in the early days of the virus.


Travelers walk past canceled flights on a schedule board, some due to the coronavirus, at the Haneda International Airport in Tokyo, Wednesday, March 18, 2020.

Eugene Hoshiko/AP

As the researchers collected data on the virus’ behaviour, they created a simulation of how it spread between travellers, starting on Jan. 10 and through to Jan 23. They found that prior to China’s lockdown on Jan. 23, an estimated 86 per cent of all COVID-19 infections were classified as undocumented.

The model continued to prove that those who caught it but failed to show symptoms for a few weeks were quietly spreading the virus at an accelerated rate.

“They’re the ones who facilitated the spread,” Shaman said.

In another study posted to medRxiv, epidemiologists who examined 91 infections in Singapore found that 48 per cent of cases were transmitted by people who had mild or no symptoms. Although they said their findings were just preliminary, this seemingly invisible transmission is something that was not as prevalent in past epidemics, such as SARS or MERS.


A woman wearing a mask walks on an empty street on Tuesday, March 17, 2020 in Paris.

Christophe Ena/AP

An interactive map by the engineering department at Johns Hopkins University tracks the confirmed cases of the virus across the world.

With a combination of manually entered data and a Chinese data source called DXY, run by the medical community and aggregated by local media and government, the map updates cases in near real-time reports, to the province level in China and country levels elsewhere. The rest of the data on new cases is pulled from social media and then confirmed with government health sources.

In Canada, while most cases to date have been travel-related, Dr. Barbara Yaffe, Ontario’s associate chief medical officer of health, has said that her department could no longer “definitively rule out community transmission,” and public health officials continue to put an emphasis on social distancing and travellers self-isolating upon their return to the country.


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Canada to donate up to 200,000 vaccine doses to combat mpox outbreaks in Africa

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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.

The Canadian Press. All rights reserved.

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How many Nova Scotians are on the doctor wait-list? Number hit 160,000 in June

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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.

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Newfoundland and Labrador monitoring rise in whooping cough cases: medical officer

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ST. JOHN’S, N.L. – Newfoundland and Labrador‘s chief medical officer is monitoring the rise of whooping cough infections across the province as cases of the highly contagious disease continue to grow across Canada.

Dr. Janice Fitzgerald says that so far this year, the province has recorded 230 confirmed cases of the vaccine-preventable respiratory tract infection, also known as pertussis.

Late last month, Quebec reported more than 11,000 cases during the same time period, while Ontario counted 470 cases, well above the five-year average of 98. In Quebec, the majority of patients are between the ages of 10 and 14.

Meanwhile, New Brunswick has declared a whooping cough outbreak across the province. A total of 141 cases were reported by last month, exceeding the five-year average of 34.

The disease can lead to severe complications among vulnerable populations including infants, who are at the highest risk of suffering from complications like pneumonia and seizures. Symptoms may start with a runny nose, mild fever and cough, then progress to severe coughing accompanied by a distinctive “whooping” sound during inhalation.

“The public, especially pregnant people and those in close contact with infants, are encouraged to be aware of symptoms related to pertussis and to ensure vaccinations are up to date,” Newfoundland and Labrador’s Health Department said in a statement.

Whooping cough can be treated with antibiotics, but vaccination is the most effective way to control the spread of the disease. As a result, the province has expanded immunization efforts this school year. While booster doses are already offered in Grade 9, the vaccine is now being offered to Grade 8 students as well.

Public health officials say whooping cough is a cyclical disease that increases every two to five or six years.

Meanwhile, New Brunswick’s acting chief medical officer of health expects the current case count to get worse before tapering off.

A rise in whooping cough cases has also been reported in the United States and elsewhere. The Pan American Health Organization issued an alert in July encouraging countries to ramp up their surveillance and vaccination coverage.

This report by The Canadian Press was first published Sept. 10, 2024.

The Canadian Press. All rights reserved.

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