Connect with us

Health

Asymptomatic COVID-19 findings dim hopes for 'herd immunity' and 'immunity passports' – CBC.ca

Published

on


A closer look at people who tested positive for COVID-19 but never developed symptoms has found that such asymptomatic carriers have few to no detectable antibodies just weeks after infection, suggesting they may not develop lasting immunity.

There’s growing evidence that a significant proportion of people who test positive for COVID-19 never show symptoms, although it’s not clear what percentage of people that is and what role they play in spreading the disease.

A Chinese study published this week in Nature followed 37 people in Wanzhou District in China who did not show any outward signs of the disease, despite testing positive when their respiratory tracts were swabbed and being kept in hospital for observation.

Some key findings include:

  • Levels of antibodies against COVID-19 were significantly lower in asymptomatic carriers than those with symptoms during active infection.

  • Antibody levels also dropped off far more quickly in people who never showed symptoms, and 40 per cent of them had no detectable antibodies eight weeks after recovery, compared with 13 per cent of symptomatic patients.

  • Those with asymptomatic infections tested positive for an average of five days longer than people with symptomatic infections — 19 days compared with 14 days — suggesting that they were shedding the virus longer.

Unlike nasal swab tests that can only detect an active infection, antibody tests can detect previous infections. But a new study suggests antibodies often don’t stick around for long after an infection. (Zuleika Chan)

The study also found that despite having no outward symptoms, 70 per cent had lung abnormalities detectable in X-rays at some point during infection — mostly spots called “ground-glass opacities,” which can indicate inflammation or other signs of disease.

No antibodies could mean no immunity, but not necessarily

Dr. Samir Gupta, a clinician-scientist at St. Michael’s Hospital in Toronto and assistant professor of medicine at the University of Toronto, noted in an interview with CBC News Network earlier this week that the study was very small.

Gupta, who wasn’t involved in the study, added that it wasn’t surprising that antibody levels fell a few months after infection. He said that’s normal, since it’s energy intensive for the body to maintain antibodies it doesn’t need.

What was “a little bit surprising,” he said, was the fact that 40 per cent of people with asymptomatic infections had no detectable antibodies at all.

WATCH | Dr. Samir Gupta on Alberta’s testing plans:

Dr. Samir Gupta says Alberta’s testing may help to understand how far the coronavirus spread but he’s doubtful we’ve reached herd immunity. 8:35

However, Gupta said, people have immunity to coronaviruses that cause common colds for only a few months, and that may also be the case for the coronavirus that causes COVID-19.

On the other hand, he said, “antibodies aren’t the whole story.”

There are other components of the immune system that play a role, such as memory cells. They remember a pathogen and begin releasing antibodies when they encounter it again, but they are hard to detect, Gupta said.

What this means for herd immunity and vaccines

Still, Tania Watts, a professor of immunology at the University of Toronto who was not involved in the study, expressed concern about the implications.

“This suggests that natural infection may not give long-lasting immunity, which is what people have been worried about,” she said.

Some countries such as Sweden and at least one Canadian province have previously suggested that one way to control the spread of COVID-19 is to allow most of the population to get infected in a controlled fashion to generate “herd immunity.” Once the population reaches a certain threshold of previous infection, there won’t be enough susceptible people to spread the virus, and it can’t spread exponentially as an epidemic.

A patient receives a shot in the first-stage safety study clinical trial of a potential vaccine for COVID-19 in March. A vaccine will need to produce a strong and long-lasting immune response, something that natural infection may not always do. (Ted S. Warren/The Associated Press)

But Watts said the low and short-lived levels of antibodies in asymptomatic infections in this study suggest we can’t rely on herd immunity being induced for long enough a period of time to have an impact.

That means we may need to wait for a vaccine that induces a stronger, longer-lived response than many natural infections, she said. “I think this puts even more pressure on vaccine development.”

What this means for antibody tests, ‘immunity passports’

Watts said another implication of the study is that serological (blood) or antibody tests — which have been touted as a way to get an idea of who has been previously infected, how much of the population that represents and how close that is to herd immunity — may not work as hoped.

And it throws cold water on the idea of controversial “immunity passports,” the idea of allowing more social interactions, such as work, travel and mass gatherings, for people who have previously been infected and therefore are immune and can’t spread the virus — which would be based on serological testing. 

“Until we know what part of the immune system is protective,” Watts said, “it’s difficult to be able to do a test and tell someone you’re safe or not.”

What this means for disease transmission

While it’s known that presymptomatic people can transmit COVID-19, it’s not really known whether people who remain asymptomatic through the course of the disease can.

Watts said she thinks the finding in this study that people without symptoms shed the virus longer than people with symptoms is “shocking” and suggests we need to worry about transmission from asymptomatic people.

“Until we have a vaccine, I think we should have very clear recommendations that everybody wears masks.”

She said the longer period of viral shedding is probably because a lack of symptoms indicate a weaker immune response, resulting in a longer time to clear the infection.

On the other hand, too intense an immune response is what puts patients in the ICU struggling to breathe.

The ideal is somewhere in between and what we’d like in a vaccine, Watts said.

“We really need that Goldilocks immune response.”

Let’s block ads! (Why?)



Source link

Continue Reading

Health

COVID-19 in B.C. alert: Eight infected individuals from Lower Mainland and Alberta attended events in Kelowna – Straight.com

Published

on


A large-scale potential COVID-19 exposure incident spanning several days in British Columbia’s Interior, involving individuals from outside the region, has prompted a public notification.

Interior Health issued a news release today (July 10) to alert anyone who attended gatherings in Kelowna’s downtown and waterfront areas from June 25 to July 6 that they might have been exposed to the coronavirus.

Eight individuals who have been tested positive for COVID-19 had attended private gatherings and visited various businesses in Kelowna, including restaurants and bars, within that time frame.

In addition, health officials are especially concerned about Canada Day and holiday weekend events.

Interior Health stated that six of the infected individuals live outside of the Interior Health region, and CBC News reported that some of the individuals were from the Lower Mainland and Alberta.

Contact tracing is currently being conducted and public health team members will inform any known contacts to isolate for 14 days.

Due to the number of locations and cases involved, anyone who attended any events on those dates is asked to monitor themselves for symptoms of COVID-19, such as fever, cough, breathing problems, loss of sense of taste or smell, fatigue, body aches, runny nose, diarrhea, headaches, sore throat, red eyes, or vomiting.

Anyone who develops symptoms should immediately self-isolated and contact healthcare providers or Interior Health testing centres to arrange for testing.

Interior Health is working with other jurisdictions to determine what the source of the outbreak is.

Over this past week, new daily case counts in B.C. have steadily increased, from seven cases on July 6 to 25 cases today.

Recent public exposure incidents have taken place at three nightlife venues in Vancouver while cases have been confirmed at a McDonald’s in Surrey, a gym in Burnaby, and flights to and from Vancouver. 

Although travel-related businesses have been reopening in B.C. as part of the province’s Phase 3 of its reopening plan, many communities remain concerned about the possibility of travellers bringing the coronavirus into their regions.

The Haida Nation is opposing the reopening of two luxury fishing lodges reopening without their consent, as they have stated that even one case of COVID-19 could be devastating to their communities due to limited healthcare services and only two ventilators available. 

More

Let’s block ads! (Why?)



Source link

Continue Reading

Health

Why it may be harder to catch COVID-19 from surfaces than we first thought – CBC.ca

Published

on


This is an excerpt from Second Opinion, a weekly roundup of eclectic and under-the-radar health and medical science news emailed to subscribers every Saturday morning. If you haven’t subscribed yet, you can do that by clicking here.


Disinfecting groceries, wiping down packages, cordoning off playgrounds. 

While those approaches to avoiding COVID-19 infection became commonplace early on in the pandemic, the virus may not transmit as easily on surfaces as was originally thought — and experts say it may be time to shift our focus on how we protect ourselves.

To date, there have been “no specific reports” of COVID-19 directly from contact with contaminated surfaces, even though research consistently shows the virus can survive on them for several hours or days, the World Health Organization said on Thursday.

The update was part of a new scientific brief released by the UN agency outlining its stance on how COVID-19 spreads, after an open letter from more than 200 experts to change its messaging on the possibility it transmits through the air.

Despite the lack of concrete evidence on surface transmission, the WHO still maintains  contaminated surfaces – also known as fomites – are a “likely mode of transmission” for COVID-19.

Surfaces ‘not a significant risk’ for COVID-19

But experts from a variety of disciplines aren’t convinced, and some warn the focus on surfaces has been overblown.

Emanuel Goldman, a microbiology professor at the New Jersey Medical School of Rutgers University, said in an article published in The Lancet journal earlier this week that the risk of COVID-19 infection from surfaces is “exaggerated.”

“This is not a significant risk,” he told CBC News. “Not even a measurable risk.”

Goldman said the evidence for infection from surfaces was based on lab experiments that were unrealistic when compared to real life situations and used extremely large amounts of virus to test if it could survive over extended periods of time.

Linsey Marr, an expert in the transmission of viruses at Virginia Tech who has studied the survival of COVID-19 on surfaces, said that while it’s possible people could get infected from surfaces, it’s still unclear if it’s actually happening.

Restaurants with patios, shopping malls and hair salons are among the businesses allowed to reopen as Toronto begins phase two of a stepped return to pre-COVID-19 operations on June 24, 2020. (Evan Mitsui/CBC)

“I think the thinking has changed,” Marr said, adding the perceived risk of transmission from contaminated surfaces is lower than it was earlier in the pandemic when not much was known about the coronavirus.

She said in order to be infected with COVID-19 from a surface, a person would have to transfer it to their fingers where it would need to survive long enough to enter the body by touching the eyes, nose or mouth. 

“We know that virus can survive [on surfaces] and then the question is, can people pick those up and transfer them into their respiratory tract?” Marr said. “You have to have a lot of virus on there to cause infections.”

The average person infected with COVID-19 also isn’t typically shedding large amounts of the virus at any given time, noted infectious disease specialist Dr. Zain Chagla, an associate professor at McMaster University in Hamilton.

“Viruses aren’t that environmentally hardy,” he added.

“They’re built to infect humans. They’re built to infect cells. As soon as they leave the human host and enter the environment, they become more and more unstable.”

Watch | Are you safer from COVID-19 indoors or outdoors?

Andrew Chang asks an infectious disease doctor whether it’s safer to be indoors or outdoors during the coronavirus pandemic. 1:02

Eugene Chudnovsky, a professor of physics at the City University of New York whose research has focused on the spread of the virus, said the threat of infection from a surface like a doorknob really depends on the conditions to which it was exposed.

“If there are just a few people touching it in an hour, it’s very unlikely it will contain the infective dose of the virus,” he said.

“But if this is a door that is getting opened every few seconds for a lengthy bit of time and there is a significant number of symptomatic infected people who are touching it during a few hours, it can accumulate a significant amount of the virus.”

Disinfecting surfaces ‘not as necessary as we thought’

One of the reasons the evidence for COVID-19 infection from surfaces is lacking is because it’s difficult to track through contact tracing.

“You can start asking people about conversations they had and places they were, but when you start asking them about surfaces they’ve touched, it gets much, much harder to really pin it down,” said Erin Bromage, an associate biology professor at the University of Massachusetts Dartmouth who researches infectious diseases.

“They’re probably associated with a few percentage of transmissions, probably at the highest, which is a lot lower than what we find say for influenza – but it seems to be not a major driver with this particular pathogen.”

The Public Health Agency of Canada maintains it is “not certain how long COVID-19 survives on surfaces,” and says the risk of infection from things like packages is low. It does, however, still list contaminated surfaces as a common route of infection.

The U.S. Centers for Disease Control and Prevention updated its guidelines on surface transmission of COVID-19 in May, saying it “may be possible” a person can get COVID-19 by touching a surface that has the virus on it but it’s not “the main way the virus spreads.”

“There’s just a growing narrative that the degree of transmission through fomites is probably less than what was earlier anticipated,” said Dr. Isaac Bogoch, an infectious disease physician at Toronto General Hospital.

“The vast majority of transmission seems to be through close contact with an infected individual, primarily in an indoor setting.”

He said the change in thinking around the risk of COVID-19 infection from surfaces means that the average person’s groceries are probably much less of a threat than a visit to the grocery store.

“It reinforces hand hygiene, but it also tells us that the need to disinfect every surface that comes into the house is probably not as necessary as we thought it was earlier on in the pandemic,” he said. “It’s not hurting anybody, but it’s just not necessary.”

WATCH | How to handle your groceries during the COVID-19 outbreak:

The coronavirus can live up to several days on some surfaces, but experts say there’s no reason to worry about the groceries you bring home. CBC News shows you how basic hygiene will keep you safe from your groceries. 1:36

Bromage, who wrote a viral blog post in May shared by millions explaining the places people are most at risk of COVID-19 infection, said the risk of transmission from surfaces on things brought into the home is “quite low” in countries like the U.S. and Canada.

“It’s probably something to be aware of,” he said, “but something that we don’t need to focus a lot of anxiety and attention on.”

Chagla said the initial focus on surface contamination also sparked a common practice that could be downright harmful: wearing latex gloves while running errands or shopping.

Discared gloves are pictured at North York General Hospital on May 26, 2020. (Evan Mitsui/CBC)

“Going to the grocery store wearing a pair of gloves is probably not the cleanest thing to be doing,” he said.

While health-care workers and food service staff wear gloves for infection control reasons, Chagla stressed they’re used for specific purposes, and short periods of time.

Wearing gloves for extended stretches while touching various objects can lead to cross-contamination the longer you’re wearing them, he said, which winds up being less helpful than just washing or sanitizing your bare hands regularly.

‘Misinterpretation’ of data

For parents of young children who are concerned about the risk of COVID-19 infection from surfaces like playgrounds, which have been off limits in cities like Toronto for months, the lack of evidence is no doubt frustrating.

Marr thinks the guidance on children avoiding playgrounds has been “misguided” throughout the pandemic.

“Playgrounds are probably one of the safer places for kids to congregate, if they have to congregate,” she said. “And the reason why is that sunlight kills off the virus pretty effectively. So if it is on surfaces, I don’t think it’s going to last very long.”

Chagla said at this point in the pandemic, there’s no “good reason” why playgrounds should remain closed, given the combination of sunlight and open-air ventilation making them a relatively low-risk activity.

Marr said the real risk of infection from playgrounds is largely from kids who are in close contact with each other, not from the surfaces they’re interacting with.

Howard Njoo, Canada’s deputy chief public health officer, said Wednesday that officials are weighing the evidence on infection in children, but that the risk seems low. 

Caution tape is wrapped around a swing set at a playground in Regina on June 10. (Kirk Fraser/CBC)

“From the science, what we know is that certainly young people, children, are less likely to have more severe consequences if they do get infected with the virus,” he said.

“It also appears that in terms of transmission, young children — at least in some of the studies i’ve seen — do not appear to be as efficient or effective in terms of transmitting the virus to others.”

Goldman said misguided policy decisions from governments and businesses pushed him to speak out about the lack of evidence for COVID-19 risk from surfaces.

“The problem is the public policy was driven by this misinterpretation of the data,” he said.

“It’s not that the data were wrong, but they were not the right data. It was not data that applied to the actual situations that are relevant.”

Goldman said these policy decisions can be “counterproductive” because they can “dilute” effective prevention measures like physical distancing and wearing a mask to stop the spread of COVID-19.

“It’s actually harmful to have the wrong interpretation of the data,” he said. 

“I think it’s time to say the emperor has no clothes.”


To read the entire Second Opinion newsletter every Saturday morning, subscribe by clicking here.

Let’s block ads! (Why?)



Source link

Continue Reading

Health

A roundup of COVID-19 developments for Friday July 10, 2020 – Winnipeg Free Press

Published

on



I suppose we shouldn’t be surprised that the bureaucratic heads of our health care systems have become household names — and even heroes — during the pandemic

Dr. Brent Roussin, Manitoba’s chief public health officer, probably has better name recognition these days than many in Premier Brian Pallister’s cabinet. In Vancouver, the larger than life faces of British Columbia’s top doctor, Dr. Bonnie Henry, and Dr. Theresa Tam, Canada’s chief public health officer, are celebrated on a mural. And south of the border, the world has frequently been hanging on every word from Dr. Anthony Fauci, the 79-year-old who is the top adviser to the White House’s coronavirus task force.

Alas, for the past two months, Donald Trump has left the good doctor hanging.

As Hannah Kuchler reveals in her interview with Fauci published by the Financial Times today, there’s now more than social distance at play between the straight-talking scientist and Trump.

“Fauci last saw Trump in person at the White House on June 2 — and says he has not briefed the president for at least two months,” writes Kuchler. “He tells me this in a matter-of-fact tone, but I suspect that his indifference is feigned. While Trump holds potential superspreader events, Fauci meets with the task force run by the vice-president. He says he is ‘sure’ that his messages are passed along — but Trump is evidently not listening. On July 4, the president declared that 99 per cent of Covid-19 cases were ‘harmless.'”

The supposed one per cent of COVID-19 cases that by extension are harmless have now led to nearly 134,000 deaths in the country Trump leads.

In that interview, the leading public health official now serving his sixth president says he understands why Fauci-mania has taken off during what he describes as a perfect storm.

“I believe, in fact I’m certain, that the country, in a very stressful time, needed a symbol of someone who tells the truth, which I do.”

I’m betting these would be far less stressful times for all if Trump had been willing to spend as much time with Fauci as he has been with Fox’s Sean Hannity over the past two months.

— Paul Samyn, Winnipeg Free Press editor


THE LATEST NUMBERS

 

Chart showing daily status cumulative counts of positive COVID-19 cases

 

Chart showing age and gender breakdown of reported COVID-19 cases

 

COVID-19 CASES IN CANADA

 

COVID-19 NEW DAILY CASES IN CANADA

 

CANADA COVID CASES OVER TIME

Note: Manitoba and Canada figures may not match due to differences in data sources.

THE LATEST IN MANITOBA

● Manitoba continues its streak of COVID-19 free days. No cases of the virus have been identified in July. The number of cases in Manitoba remains at 325. There are four active cases, but none that require hospitalization. A total of 314 individuals have recovered from COVID-19. Seven people have died. A further 928 laboratory tests were performed on Thursday, bringing the total number of tests since early February to 69,036. 

THE LATEST ELSEWHERE

 ● Starbucks will be requiring customers to wear facial coverings while visiting all company-owned café locations in the U.S., beginning Wednesday. The company said in a blog post that at select locations where a local government mandate is not in place, customers not wearing a facial covering will have various options to order their items, including drive-thru and curbside pickup.

● An online poll by Leger and the Association for Canadian Studies released this week found 86 per cent of respondents in Canada are opposed to letting U.S. tourists north of the border. An Abacus Data poll out Friday found much the same thing. And when Rep. Brian Higgins, a New York Democrat, updated his bipartisan call for a plan to reopen the border, the ensuing Twitter barrage of sarcasm, satire and outright anger belied Canada’s reputation as a bastion of civility, replete with memes of building walls, slamming doors and Bugs Bunny taking a handsaw to the 49th parallel. “I don’t blame them for wanting us out of there,” the congressman said Friday.

● Unions representing Ontario’s health-care workers are consulting with their memberships about taking political action in response to the province potentially extending its emergency act. The Ontario Council of Hospital Unions/Canadian Union of Public Employees says that under the emergency orders their collective bargaining agreement with the province is suspended. Michael Hurley, president of the unions, says that while that was acceptable in the early stages of the COVID-19 pandemic, it’s now a detriment to health-care workers. He says that nurses and other care workers can have their shifts changed, be moved from site to site, or have vacation requests denied under the act.

● Nevada Gov. Steve Sisolak says the state will re-implement restrictions on bars and restaurants in certain counties to prevent further spread of the coronavirus after a spike in confirmed cases. Sisolak’s newest order began Friday at midnight. It requires bars that do not serve food to close their doors. Restaurants will stop serving parties of six or more. The directive includes Washoe and Clark County, home to Reno and Las Vegas. The directive is the second time Nevada has tightened restrictions since the state began reopening. The number of confirmed cases rose, prompting the governor to announce a statewide mask mandate on June 24.

● A medical association that the White House has cited in its press to reopen schools is pushing back against President Donald Trump’s repeated threats to cut federal funding if schools don’t open this fall. In a joint statement with national education unions and a superintendents group, the American Academy of Pediatrics on Friday said decisions should be made by health experts and local leaders. The groups argued that schools will need more money to reopen safely during the coronavirus pandemic and that cuts could ultimately harm students. “Public health agencies must make recommendations based on evidence, not politics,” the groups wrote in the statement.

ODDITY

 “No shirts, no shoes, no mask — no service.”

— Michigan Gov. Gretchen Whitmer, mandating businesses open to the public deny service or entry to customers who refuse to wear one.

QUOTE, UNQUOTE

 

LOCAL NEWS

NATIONAL NEWS

INTERNATIONAL NEWS

COVID-19 BASICS

Let’s block ads! (Why?)



Source link

Continue Reading

Trending