Tag Archives: transmission

Study offers ‘promising’ evidence that at least 1 COVID-19 vaccine may curb virus transmission

Real-world findings are starting to back expectations for the level of protection provided by several leading coronavirus vaccines, but there’s still a burning question among scientists: Could the shots actually reduce virus transmission as well?

New research out of Israel offers early clues that at least one vaccine — the mRNA-based option from Pfizer-BioNTech, which is also being used here in Canada — may lead to lower viral loads, suggesting it might be harder for someone to spread the virus if they get infected post-vaccination.

In a study released publicly on Monday as an unpublished, non-peer-reviewed preprint, a team of researchers from the Israel Institute of Technology, Tel Aviv University and Maccabi Healthcare Services found the viral load was reduced four-fold for infections that occur 12 to 28 days after a first dose of the vaccine.

“These reduced viral loads hint to lower infectiousness, further contributing to vaccine impact on virus spread,” the researchers wrote.

Virologist Jason Kindrachuk, an assistant professor in the department of medical microbiology at the University of Manitoba, said it’s been a waiting game to figure out whether the protection from illness offered by mRNA vaccines might also curb transmission — a key tool for winding down the pandemic.

“So the data from this, I think, is important,” he said. “It doesn’t answer all the questions, but it starts to tell us that there actually might be some added benefit to these vaccines beyond just reducing severe disease.”

Toronto-based infectious disease specialist Dr. Isaac Bogoch, a member of Ontario’s vaccine task force, agreed these early findings — which still require peer-review — aren’t a scientific “home run,” but do offer hope in the fight against COVID-19.

“This would point in the direction that people who have been vaccinated, who are still infected, may be less likely to transmit starting at about 12 days after their vaccine,” he said.

‘Significantly reduced’ viral loads

Israel is among the world leaders for COVID-19 vaccination rates, with Maccabi Healthcare Services vaccinating more than 650,000 people by Jan. 25, the paper noted, giving the researchers a large pool of data compared to what exists so far in many other countries. 

The team analyzed COVID-19 test results from roughly 2,900 people between the ages of 16 and 89, comparing the cycle threshold values of post-vaccination infections after a first dose with those of positive tests from unvaccinated patients.

So, what are cycle threshold values, and how does that potentially tie to viral loads and virus transmission?

Standard polymerase chain reaction (PCR) tests for COVID-19 identify the viral infection by amplifying the virus’s RNA until it hits a level where it can be detected by the test. Multiple rounds of amplification may be required — and the cycle threshold value refers to the number of rounds needed to spot the virus.


Toronto-based infectious disease specialist Dr. Isaac Bogoch, a member of Ontario’s vaccine task force, agrees these early findings — which still require peer-review — offer some hope in the fight against COVID-19. (Maggie MacPherson/CBC)

“If you can detect the virus with very few cycles, there’s probably a lot of virus there,” Bogoch explained. “If you need to keep looking and looking and looking and looking for it, it might be there — it’s just a lot harder to find evidence of the virus genetic material.”

A higher cycle threshold, then, usually means there’s less virus genetic material present, which usually translates to people being less contagious, he said.

Based on an analysis comparing post-vaccination test results up to Day 11 to the unvaccinated control group, the Israeli researchers found “no significant difference” in the distribution of cycle threshold values for several viral genes.

That changed by 12 days after vaccination, with the team finding a “significant” increase in cycle thresholds up to 28 days later.


A team of researchers from the Israel Institute of Technology, Tel Aviv University and Maccabi Healthcare Services found the viral load was reduced four-fold for infections happening 12 to 28 days after a first dose of the Pfizer-BioNTech mRNA vaccine. The findings have yet to be peer-reviewed and published in a medical journal. (Evan Mitsui/CBC News)

The result suggests infections occurring 12 days or longer following just one vaccine dose have “significantly reduced viral loads, potentially affecting viral shedding and contagiousness as well as severity of the disease,” the team concluded.

It’s a finding that appears to mimic the efficacy of the Pfizer-BioNTech vaccine in its clinical trials, which offered some early protection starting 12 days after the first dose and fully kicks in a week after the second shot, with a reported efficacy of around 95 per cent.

More research needed, experts say

The observational study was not a randomized controlled trial — meaning researchers couldn’t conclude a direct cause-and-effect relationship — and has not yet been published in a scientific journal. The research also has notable limitations, its authors acknowledged. 

For one, the group of vaccinated individuals may differ in key ways from the demographically matched control group, such as their general health. The study also didn’t account for variants of the virus that may be associated with different viral loads, the team wrote.

Indeed, those variants are already proving to be roadblocks in the fight against COVID-19, with concerns ranging from higher transmissibility to reduced vaccine efficacy, including concern in South Africa and beyond after a small and yet-to-be-published study suggested the Oxford-AstraZeneca vaccine offered minimal protection against mild infection from the country’s now-dominant B1351 variant. 

With those concerns in mind, experts who spoke with CBC News about the Israeli study stressed that more research is needed to back up the results on a broader scale, and among diverse populations, before being used to fuel policy changes or current approaches to vaccination efforts.

“The data needs to be reviewed by experts and confirmed that it stands up to the quality that we would want to make a conclusion,” said vaccinologist Alyson Kelvin, an assistant professor at Dalhousie University in Halifax who works with Canadian vaccine developer VIDO-InterVac in Saskatoon.

WATCH | The impact of variants on the race to vaccinate: 

South Africa has halted its rollout of the AstraZeneca COVID-19 vaccine after a study showed it offered minimal protection against mild infection from a variant spreading there. While experts say it’s cause for concern, they say vaccines can be reconfigured to protect against mutations. 2:01

Even so, Kelvin said the data appeared to be treated with the necessary caution, and offers “promising evidence,” while Kindrachuk remains optimistic as well that the findings could prove a useful starting point.

“While we still have to have people using masks, and while we still have to have people distanced, the vaccines may actually also be able to reduce transmission,” he said. 

“So, those trends that we’re hoping to see, in regards to trying to curb community transmission for SARS-CoV-2, may be accelerated with a vaccine — and that will hopefully help us get out of this a little bit sooner.”


The Current21:46Vaccine concerns in South Africa

South Africa is facing another hurdle in its fight against COVID-19 after a new study suggested the Oxford-AstraZeneca vaccine is largely ineffective against the dominant variant spreading in that country. Dr. Rinesh Chetty, who works on the front lines of the pandemic in Durban, South Africa, weighs in on the findings. And Dr. Gerald Evans, an infectious disease specialist at Queen’s University and the Kingston Health Sciences Centre, tells us what it means for Canada’s vaccination efforts. 21:46

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COVID-19 can sometimes be spread by airborne transmission, CDC says

U.S. Centers for Disease Control and Prevention (CDC) on Monday updated its guidance saying COVID-19 can sometimes be spread by airborne transmission.

It said some infections can be spread by exposure to virus in small droplets and particles, or aerosols, that can linger in the air for minutes to hours. 

Monday’s update acknowledges published reports that showed limited, uncommon circumstances where people with COVID-19 infected others who were more than 6 feet away or 2 meters or shortly after the COVID-19-positive person left an area, the agency said.

In these instances, the CDC said transmission occurred in poorly ventilated and enclosed spaces that often involved activities that caused heavier breathing, like singing or exercise.

Last month, the CDC published — and then took down — its guidance warning possible airborne transmission of the novel coronavirus.

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Controversy over airborne transmission of COVID-19 ‘a tempest in a teapot,’ Dr. Bonnie Henry says

B.C.’s provincial health officer says the controversy over airborne transmission of COVID-19 has been overblown, after hundreds of scientists signed a letter calling for the World Health Organization to revise its recommendations.

In an open letter to the WHO, 239 scientists in 32 countries have reportedly argued particles smaller than what has previously been reported can carry the novel coronavirus and infect people. According to a story in the New York Times, those scientists want the global health body to begin treating COVID-19 as an airborne illness.

But Dr. Bonnie Henry suggested Monday that the letter was designed “to foment a bit of controversy,” and the disagreement is part of an ongoing discussion about how coronaviruses and other illnesses like influenza are spread.

“I actually think it’s a little bit of a tempest in a teapot in that we all agree on the extremes and we’re fussing a little bit about how much we need to focus on the bits in the middle,” Henry said during Monday’s COVID-19 briefing.

With airborne viruses like the measles and smallpox, tiny disease-carrying particles can float in the air for hours, even travelling down hallways and through ventilation systems.

The WHO and Henry have maintained since the beginning of the pandemic that the coronavirus is spread through droplets expelled from the mouth and nose, which fall from the air comparatively quickly.

“We know that there’s a gradation of how droplets come out when somebody coughs or sneezes or talks,” Henry explained Monday.

WATCH | Scientists call on WHO to update guidance on airborne transmission of coronavirus:

A group of 239 scientists from around the world say there is enough evidence that the coronavirus can spread by airborne transmission and urged the World Health Organization to revise its guidelines, but there is debate within the scientific community. 1:55

“It is the smaller ones that can be breathed deep into the lungs, and it’s the larger ones that can often be deposited up in the back of the throat or in the back of the lungs.”

‘It’s not transmitted long distances’

The novel coronavirus appears to spread predominantly through larger droplets, according to Henry. She said that, generally, transmission of this virus requires more moisture and closer contact between people.

‘It’s not transmitted long distances in the air column. We’re all on the same page about that,” Henry said.

“Where there’s a challenge is how much of it is transmitted through the small droplets that are transmitted when I’m close to you.”


The WHO has said the coronavirus mainly spreads through larger droplets, like the ones captured in this image of a sneeze. (Lydia Bourouiba/MIT/JAMA Networks)

She said B.C.’s approach to COVID-19 depends on implementing several different layers of protection that prevent transmission of both small and large droplets. That includes several types of personal protective equipment in health-care settings, along with personal measures like physical distancing and masks in crowded settings.

“It is important to continue to look at the data, to look at where we’re seeing transmission events and adapt if we need to and put in additional measures,” Henry said.

That could include stricter rules around face masks.

“I really hope that this stimulates more innovation in things like more effective and easier to wear masks that we can use repeatedly that are much more effective,” Henry said.

“It discourages me that we’re here after SARS in 2003 and H1N1 in 2009 and we still don’t have a decent fitting mask that can be used easily in all health-care settings.”

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Scientists try to ‘see’ invisible transmission of coronavirus through respiratory droplets

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.


The coronavirus that causes COVID-19 spreads through droplets that we spew as we breathe, talk, cough and sneeze — so tiny that they’re invisible to the naked eye. 

That’s why questions remain about the virus’s transmission and what precautions need to be taken to curb its spread as governments begin to lift restrictions. Will it help if everyone wears a mask? Is keeping everyone two metres apart far enough?

Some researchers aim to learn more about transmission by trying to make invisible sneezes, coughs and breaths more visible. Here’s a closer look at that research and what it might reveal.

How do scientists think COVID-19 is transmitted?

According to the World Health Organization, the disease spreads primarily through tiny droplets expelled when a person infected with SARS-CoV-2 sneezes, coughs, exhales or spits while talking. They can infect another person who:

  • Comes into contact with those droplets through their eyes, nose or mouth (droplet transmission).

  • Touches objects or surfaces on which droplets have landed and then touches their eyes, nose or mouth (contact transmission).

The WHO says it’s important to stay “more than one metre away” from a person who is sick. But the Public Health Agency of Canada recommends staying a distance of at least two metres or two arms’ lengths away, not just from people who are sick but from all people you don’t live with.

Why is 2 metres the recommended distance for preventing transmission?

Scientists in the 19th century showed respiratory droplets from a person’s nose and mouth can carry micro-organisms such as bacteria and viruses.

Then, in 1934, W.F. Wells at the Harvard School of Public Health showed that large droplets (bigger than 0.1 millimetre) tended to fall and settle on the ground within a distance of two metres, while smaller droplets evaporated and the virus particles left behind could remain suspended in the air for a long time.


Wells proposed that could explain how diseases are transmitted.

Since then, respiratory diseases have been divided into those transmitted via droplets (usually from close contact) and those that are airborne and can spread over longer distances, such as measles or tuberculosis. 

Such tiny particles are presumably pushed around by air currents, but can’t move easily due to air resistance. So their actual movements haven’t been well modelled or measured, said Lydia Bourouiba, professor and director of the Fluid Dynamics of Disease Transmission Laboratory at the Massachusetts Institute of Technology. 

“And that’s why the notion of airborne [transmission] is very murky,” said Bourouiba, who is Canadian.

Why don’t experts think the virus is airborne?

A pair of recent studies raised the notion of airborne transmission, but Mark Loeb, a professor at Hamilton’s McMaster University who specializes in infectious disease research, cautions against putting too much stock in them. 

Researchers found traces of RNA from SARS-CoV-2 in washrooms and some high-traffic areas in hospitals in Wuhan, China, and in Nebraska, and suggested it got into those areas through the air, though there was no evidence the particles were still infectious. 


Government guidelines in Canada recommend that people stay at least two metres away from others as part of physical distancing measures to curb the spread of COVID-19. (Gary Moore/CBC)

Loeb said that’s just a “signal” that part of the virus was there. 

“Does it mean that COVID-19 is spreading from person to person through aerosols? I would say definitively not,” Loeb said. 

If the virus were airborne, we’d know by now, said Dr. Allison McGeer, because every health care worker would be infected despite wearing personal protective equipment.

“You and I don’t have to worry walking down the street that we’re going to be breathing the air of somebody who walked down the street five minutes ahead of us who had COVID-19 and didn’t know it,” said McGeer, an infectious disease specialist with Sinai Health in Toronto who is leading a national research team studying how COVID-19 is transmitted. “That we can be confident about.”

Is there evidence the virus could be spread farther than 2 metres?

Some studies, including Bourouiba’s, show that droplets from coughs and sneezes can, in fact, travel much farther than expected. Bourouiba’s high-speed imaging measurements and modelling show smaller respiratory droplets don’t behave like individual droplets but are in a turbulent gas cloud trapping them and carrying them forward within it. The moist environment reduces evaporation, allowing droplets of many sizes to survive much longer and travel much farther than two metres — up to seven or eight metres, in the case of a sneeze

WATCH | Close-up view of the droplets released by a person sneezing

(Credit Lydia Bourouiba/MIT/JAMA Networks)

She said the research “is about revealing what you cannot see with the naked eye.”

A more recent Canadian study used a “cough chamber” to show that if someone coughs without covering their mouth, droplets from the cough are still travelling at a speed of about one kilometre per hour when they hit the two-metre edge of the chamber. Within the chamber, droplets remained suspended for up to three minutes. 

WATCH | The speed and distance travelled by droplets from a cough

Dr. Samira Mubareka, a virologist at Sunnybrook Hospital in Toronto who co-authored the study, said it “gives you a sense of what the possibilities are,” but noted that the researchers, who were studying flu patients, detected very little virus in the droplets.

What does that say about the 2-metre guideline?

Bourouiba says her research points to the potential for exposure beyond two metres from someone who is coughing and sneezing. As she wrote in the journal JAMA Insights in March, that means it’s “vitally important” for health care workers to wear high-grade personal protective equipment in the form of respirators even if they’re farther than two metres away from infected patients.  

However, she does think two metres can be far enough for healthy people in the general public in most environments, since breathing and talking don’t propel droplets and surrounding cloud too far.

Mubareka stands by the two-metre guideline despite the findings of her cough chamber study.

Because despite dramatic images of respiratory droplets being propelled from someone’s nose and mouth, it’s not yet clear how many of them contain virus and how many are infectious.

“And that’s really the key variable — that’s what really determines your risk,” she said. “Those are the kinds of things we haven’t been able to measure.” That may change, she added, with the recent invention of particle samplers designed specifically for viruses.

Loeb of McMaster, notes that a cough chamber and similar laboratory setups are highly artificial settings and controlled environments.

“They’re basically saying what’s theoretically possible,” he said. “I think those are provocative and those are hypothesis- generating, but then they need to be tested in the field.”

Loeb is running such a field test himself — a randomized controlled trial of the use of medical versus N95 masks among health care workers to see if there is a difference in the transmission of COVID-19.

But are coughing and sneezing all we need to worry about?

That’s a question on a lot of people’s minds, given that a growing number of studies have shown asymptomatic and pre-symptomatic transmission is possible, especially among those who live with an infected person. 

Even though researchers aren’t sure exactly how people without symptoms transmit the disease, the new evidence has prompted both U.S. and Canadian officials to suggest apparently healthy people wear masks in public to protect others — “because it prevents you from breathing or speaking moistly on them,” Prime Minister Justin Trudeau famously explained.

“People generate particles when they’re talking, singing, breathing — so you don’t have to necessarily be coughing,” Mubareka said. “It’s just that maybe the dispersion is a little bit more limited.” 

WATCH | The droplets produced when someone speaks with, and without, a mask

This video, from a study published in April 2020 the New England Journal of Medicine by researchers at the U.S. National Institutes of Health, uses laser light scattering to show droplets produced when someone speaks. 0:42 

A recent brief video and report by U.S. National Institutes of Health researchers used lasers to show that droplets projected less than 10 centimetres when someone says the phrase “Stay healthy.” It found the louder someone spoke, the more droplets were emitted.

But they were dramatically reduced if a damp washcloth — a stand-in for a mask — was placed over the speaker’s mouth.

So what about using masks to curb the spread of COVID-19?

Studies have already provided evidence that the rate at which sick people shed the virus into their surroundings is reduced when they wear a mask. 

Other studies, such as a 2009 paper in Journal of the Royal Society Interface, use imaging to show how wearing a mask while coughing reduces the jet of air that’s normally directed forward and down. A surgical mask “effectively blocks the forward momentum of the cough jet and its aerosol content,” the study found. Some does leak out the sides, top and bottom, but without much momentum.


A 2009 study by researchers in the U.S. and Singapore uses schlieren imaging to show airflow from a person’s mouth a) without a mask b) with a medical mask and c) with an N95 mask. (Gary S. Settles/Penn State University/Journal of the Royal Society Interface)

The World Health Organization recommends that people wear masks if they are coughing and sneezing or if they are caring for someone who is sick.

It notes that studies haven’t been conducted yet on whether or not transmission is reduced when healthy people wear masks in public, but it encourages countries to look into that. 

Many governments haven’t waited. Los Angeles, Italy and Austria are among the places that have begun requiring customers to wear masks while shopping


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

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China confirms human-to-human transmission of new coronavirus

Human-to-human transmission has been confirmed in an outbreak of a new coronavirus, the head of a Chinese government expert team said Monday.

Team leader Zhong Nanshan, a respiratory expert, said two people in Guangdong province in southern China caught the disease from family members, state media said.

The National Health Commission task force also found that some medical workers have tested positive for the virus, the English-language China Daily newspaper said. 

Human-to-human transmission could make the virus spread more quickly and widely. The outbreak is believed to have started from people who picked it up at a fresh food market in the city of Wuhan in central China. 

Zhong said the two people in Guangdong had not been to Wuhan but family members had returned from the city, the China Daily said.

The official Chinese Xinhua News Agency reported that as of 6 p.m. local time on Jan. 20, a total of 224 cases of pneumonia of new coronavirus infection were reported in China, including 217 confirmed cases:

  • 198 in Wuhan.
  • Five in Beijing.
  • Fourteen in Guangdong.
  • Seven suspected cases: two cases in Sichuan, one case in Yunnan Province, two cases in Shanghai, one case in Guangxi Zhuang Autonomous Region, and one case in Shandong Province). 

Authorities elsewhere also announced cases in other Chinese cities for the first time.

Thailand, Japan, South Korea report cases

Zhong said the two people in Guangdong had not been to Wuhan but fell ill after family members had returned from the city, the China Daily said.

The outbreak has put other countries on alert as millions of Chinese travel for Lunar New Year.

Authorities in Thailand and in Japan have already identified at least three cases, all involving recent travel from China.

China says its acting responsibly and openly to safeguard the world from the new coronavirus 0:38

South Korea reported its first case Monday, when a 35-year-old Chinese woman from Wuhan tested positive for the new coronavirus one day after arriving at Seoul’s Incheon airport. The woman has been isolated at a state-run hospital in Incheon city, just west of Seoul, the Korea Centers for Disease Control and Prevention said in a statement.

At least a half-dozen countries in Asia and three U.S. airports have started screening incoming airline passengers from central China.

The virus belongs in the same family of coronaviruses as Severe Acute Respiratory Syndrome (SARS), which killed nearly 800 people globally during a 2002-03 outbreak that also started in Guangdong, China. In Canada, 44 people died, many of them health-care workers.


What are public health officials saying in Canada?

  • The virus belongs in the same family of coronaviruses as Severe Acute Respiratory Syndrome (SARS). Public Health Agency of Canada (PHAC) told CBC News Sunday that “the overall risk of disease spread to Canada is considered low.” 
     
  • Canada has no direct flights from Wuhan, and the volume of travellers arriving indirectly from Wuhan is low, PHAC said. 
     
  • PHAC said it will be “implementing additional measures” in the coming week, including warning signs at airports in Toronto, Vancouver and Montreal.
     
  • U.S. officials have said they will begin screening travellers coming from Wuhan at three major airports — New York City’s JFK International Airport, San Francisco International Airport and Los Angeles International Airport.

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‘Possible’ there was limited human-to-human transmission of new coronavirus in China, WHO says

There may have been limited human-to-human transmission of a new coronavirus in China within families, and it is possible there could be a wider outbreak, the World Health Organization (WHO) said on Tuesday.

Coronaviruses are a large family of viruses that can cause infections ranging from the common cold to SARS. A Chinese woman has been quarantined in Thailand with a mystery strain of coronavirus, Thai authorities said on Monday, the first time the virus has been detected outside China.

In all, 41 cases of pneumonia have been reported in the central Chinese city of Wuhan, which preliminary lab tests cited by state media showed could be from a new type of coronavirus, and one patient has died. There have since been no new cases or deaths, Wuhan health authorities said on Tuesday.

“From the information that we have it is possible that there is limited human-to-human transmission, potentially among families, but it is very clear right now that we have no sustained human-to-human transmission,” said Maria Van Kerkhove, acting head of WHO’s emerging diseases unit.

The WHO is however preparing for the possibility that there could be a wider outbreak, she told a Geneva news briefing. “It is still early days, we don’t have a clear clinical picture.”

Some types of the virus cause less serious diseases, while others — like the one that causes MERS — are far more severe.

The UN agency has given guidance to hospitals worldwide about infection prevention and control in case the new virus spreads. There is no specific treatment for the new virus, but anti-virals are being considered and could be “re-purposed,” Van Kerkhove said.

With Chinese New Year approaching on Jan. 25, when many Chinese tourists visit Thailand, the WHO called on Thai authorities, the public and holidaymakers to be on alert.

Richard Brow, the agency’s representative in Thailand, said anyone with a fever and cough who had spent time in Wuhan should get checked out by a health worker.

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Drug treatment stopped transmission of HIV in gay couples, study finds

A European study of nearly 1,000 gay male couples who had sex without condoms — where one partner had HIV and was taking antiretroviral drugs to suppress it — has found the treatment can prevent sexual transmission of the virus.

After eight years of follow-up of the so-called serodifferent couples, the study found no cases at all of HIV transmission within couples.

The study proves, the researchers said, that using antiretroviral therapy (ART) to suppress HIV to undetectable levels also means it cannot be passed on via sex.

“Our findings provide conclusive evidence for gay men that the risk of HIV transmission with suppressive ART is zero,” said Alison Rodger, a professor at University College London who co-led the research.

She said this “powerful message” could help end the HIV pandemic by preventing the virus’ transmission in high-risk populations. In this study alone, for example, the researchers estimate that the suppressive antiretrovial treatment prevented around 472 HIV transmissions during the eight years.

The study was published in the Lancet medical journal on Thursday. Its findings add to an earlier phase of the study which looked at HIV transmission risk for serodifferent heterosexual couples who also did not use condoms. It also found zero risk.

The Ontario government will start paying for a drug that can protect sexually active people from HIV infection 1:56

While 15 of the men among the 972 gay couples in this phase did become infected with HIV during the eight years of follow-up, genetic testing showed their infections were with strains of HIV acquired from another sexual partner.

The new findings aren’t surprising but are great news nonetheless, said Dr. Darrell Tan, an infectious diseases physician at St. Michael’s Hospital in Toronto. He’s prescribed and studied suppressive antiretrovial treatment, as well as pre-exposure prophylaxis (PrEP) — medication taking by an HIV negative partner to prevent transmission from happening should they be exposed to the virus. 

But antiretroviral therapy and PrEP is expensive and access is uneven across Canada, Tan said. 

“The data are so compelling there’s not only direct clinical benefits, there’s direct preventative benefits as well,” Tan said. “We need to have universal access.” 

The cost of PrEP and stigma of HIV might explain why every year in Canada up to 3,000 people are infected.

Since the start of the AIDS epidemic in the 1980s, more than 77 million people have become infected with HIV worldwide. Almost half of them, 35.4 million, have died of  AIDS-related illness.

Rachel Baggaley, the World Health Organization’s co-ordinator for HIV prevention and testing, said this latest study “adds to the clear and consistent evidence” that HIV transmission to sexual partners does not occur when someone with HIV is on antiretroviral therapy (ART) and their virus is suppressed.
 
“Increasing access to HIV testing [and] ART … remains critical for individuals and is central to the HIV public health 
response,” she said. 

Global health experts say the fight against HIV is at a precarious point, with the annual number of AIDS deaths falling and the number of people getting antiretroviral treatment rising, while the number of new infections is stubbornly high at around 1.8 million new cases per year.

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