How does the new coronavirus disease, Covid-19, spread? That’s just one of many basic, unanswered questions about this latest pandemic threat.
The virus that causes Covid-19 — known as SARS-CoV-2 — has already infected more than 75,000 people in two months. (Of them, 2,130 have died.) And the best explanation for this rapid spread is that it’s being passed through droplets from coughing or sneezing. When these virus-laden droplets from an infected person reach the nose, eyes, or mouth of another, they can transmit the disease.
But are there other ways SARS-CoV-2 moves between people? And what do they tell us about why this disease seems to be even more contagious than SARS and MERS? The latest science on the virus offers possible answers to these questions — and why Covid-19 might be particularly difficult to stop. Here’s what we know so far.
Respiratory illnesses generally fall into two categories: upper respiratory — infections in the nose, pharynx, or larynx, like the common cold and seasonal influenza; and lower respiratory illnesses, like pneumonia, which infect the lungs.
The original SARS virus that spread around the world in 2003 was thought to be a lower respiratory infection: It replicated in the cells deep within the lungs and caused the pneumonia. People also seemed to only spread the virus days into their illness, when it was already clear they were sick. This made SARS more difficult to pass on to others and the job of containing it relatively easy.
The new virus that causes Covid-19 disease appears to be a different beast: While it also can eventually lead to pneumonia, the virus does a great job of replicating in the upper respiratory tract, even when people don’t have any symptoms or just begin to feel sick.
Check out this new New England Journal of Medicine paper. Chinese researchers monitored how much virus could be found in the upper respiratory tracts — noses and throats — of 18 patients in Guangdong, China. One of the 18 never had any symptoms.
The big finding? The way people shed this virus, potentially exposing others, looked a lot more like the flu than the first SARS, which might help explain why Covid-19 appears to be more infectious. You can see why in this chart from the study, focused on the patients who experienced symptoms: Just as they were starting to feel ill, they had the highest concentrations of virus in their noses:
What’s more, the one person who was asymptomatic carried a similar amount of virus as the symptomatic patients, “which suggests the transmission potential of asymptomatic or minimally symptomatic patients,” the researchers wrote.
In a separate, newly published New England Journal of Medicine paper, researchers in Germany were also able to isolate the virus from patients’ upper respiratory tract even before they showed any symptoms or were very mildly symptomatic — more evidence of the potential for spread of the virus from the nose and throat when people barely know they’re sick.
So what does this imply about the contagiousness of Covid-19 and stopping the outbreak? “For a virus pretty closely related to SARS, it shows very effective person-to-person transmission, something nobody really expected,” Stephen Morse, a professor of epidemiology at Columbia University Mailman School of Public Health, told Vox. Researchers currently believe one infected person generally infects two to more than three others, which would make the new coronavirus more contagious than seasonal flu, SARS and MERS.
Javier Zarracina and Christina Animashaun/Vox
Second, it means stopping the outbreak might be more difficult, since people start to become infectious early on in their disease or may even spread the virus when they’re asymptomatic.
But to confirm these two findings, we’ll need more science, saidJennifer Nuzzo, an infectious disease expert and senior scholar at the Johns Hopkins Center for Health Security. “We still don’t know to what extent people without symptoms can infect,” she pointed out.
It’s also possible that transmission early in the illness or from asymptomatic people won’t end up being important contributors to the outbreak, said Marion Koopmans, who studies emerging infectious diseases and heads the department of virology at the Erasmus Medical Center in Rotterdam, Netherlands. In most parts of the world where travelers with Covid-19 turned up, she added, the spread of the disease has been contained by only testing people with symptoms. But, she added, “both of these statements can coexist: Asymptomatic shedders could spread the virus, but it probably is not the main driver of this epidemic.”
Another way viruses can spread is through poop. Think of the norovirus, the extremely contagious bug that can be passed along by ingesting the stool of an infected person, often through food or touching a contaminated surface. This is known as the “fecal-oral” route of disease transmission.
Now there’s some suggestion in the emerging literature that Covid-19 could be passed through exposure to virus-laden feces, too.
As with norovirus, this means the disease could be passed around when there’s less than optimal hygiene. “If true, it would not be surprising,” Morse said. “A number of other coronavirus are excreted from the intestines, and infectious virus can be found in stool.”
That’s why the China CDC recommended taking measures to stop the spread of the virus this way, including:
maintaining environmental health and personal hygiene; drinking boiled water, avoiding raw food consumption, and implementing separate meal systems in epidemic areas; frequently washing hands and disinfecting of surfaces of objects in households, toilets, public places, and transportation vehicles; and disinfecting the excreta and environment of patients in medical facilities to prevent water and food contamination from patients’ stool samples.
But just because the virus is found in stool doesn’t mean that’s how it’s transmitting. And, again, more research is needed to figure out how important the fecal-oral route is in the spread of this disease.
Poop was also implicated in the first SARS outbreak, when a large housing estate in Hong Kong called Amoy Gardens became ground zero of a public health nightmare. More than 300 people were infected with the disease through yet another viral transmission route: airborne transmission of virus-ridden feces aerosols.
Airborne spread happens when the residue from evaporated, infected droplets gets suspended in the air and indirectly infects those who breathe it in. It’s different from droplet transmission, since droplets are too large to float through the air and need to get sprayed directly on someone’s eye, nose, or mouth in order to infect them.
In the case of Amoy Gardens, researchers learned SARS was capable of going airborne, spreading through the building’s faulty plumbing and ventilation systems to the people who lived on the estate. “The infections [were] officially attributed to faulty toilet traps which were thought to have aerosolized patients’ virus when the toilet was flushed, allowing dispersal of the virus to other residents,” Morse explained. “This has been demonstrated with SARS and MERS and others, and therefore is plausible, although we currently lack good evidence.”
So researchers and doctors are looking into whether the news SARS virus spreads this way — and taking precautions in case it can. Vito Iacoviello, chief of the division of infectious diseases at Mount Auburn Hospital in Cambridge, Massachusetts, and an editor at Dynamed, noted that the US Centers for Disease Control and Prevention is recommending people admitted to hospitals with Covid-19 be put in an airborne isolation room. “That’s the precaution we use for TB, measles, and chickenpox,” he said, and it suggests health officials are preparing for the possibility that this virus is capable of airborne spread.
But again, for now, there’s no good evidence of Covid-19’s airborne transmission. It’s just another thing to watch out for as our understanding of this virus, and how it moves through populations, evolves.
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.
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.
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