More than seven months after the new coronavirus was first detected, scientists and health experts are still trying to get a better understanding of how it spreads and how to curb the COVID-19 respiratory disease it causes.
The coronavirus is transmitted from person to person through “droplet transmission”, including direct contact with someone who has been infected, indirect contact with contaminated surfaces, droplets of saliva from coughing or discharge from the nose when sneezing, according to the World Health Organization (WHO).
Airborne transmission is also possible, but its effects and risks have recently sparked a scientific debate.
What is airborne transmission?
The WHO has long said the new coronavirus spreads mainly through small droplets released from the mouth and nose that fall from the air in a short period.
But some scientists and researchers are increasingly pointing out to evidence that the virus can also be transmitted by even smaller droplets called aerosols. Usually generated when people are shouting and singing, these remain suspended in the air for longer and can travel farther.
How is it different from droplet transmission?
The respiratory droplets sneezed or coughed out are larger in size – a diameter of five to 10 micrometres – and the range of exposure is one to two metres (three to six feet).
Aerosols, however, are less than five micrometres in diameter and travel beyond two metres from the infected individual.
“The new coronavirus can survive in both droplets and aerosol for up to three hours under experimental conditions, although this depends on temperature and humidity, ultraviolet light and even the presence of other types of particles in the air,” Stephanie Dancer, a consultant medical microbiologist in the UK, told Al Jazeera.
“Microscopic aerosols can project at least six metres in indoor environments, and possibly even further if dynamic air currents are operating. The distance depends upon how large the aerosol is.”
Animation: How does coronavirus behave?
How is COVID-19 spreading through the air?
As in droplet transmission, aerosols can be released in several ways including, breathing, talking, laughing, sneezing, coughing, singing and shouting.
“Breathing would not offer much projectile force, but shouting, singing, coughing and sneezing project aerosol through the air with a range of different velocities,” said Dancer.
“Even if one individual particle does not contain enough virus to cause infection, if you carry on breathing in these particles over time, you will acquire enough in your mouth, nose and respiratory tract to initiate infection.”
Airborne transmission can also occur in certain medical procedures that involve the patient generating aerosols, putting healthcare workers particularly at risk.
“Coronavirus can be spread by aerosol under special circumstances if using nebulisers, bronchoscopy, intubation, dental and other oral procedures using suction and lavage,” said Naheed Usmani, president of the Association of Physicians of Pakistani Descent of North America (APPNA).
“This is particularly dangerous for healthcare workers who should only attempt these procedures wearing proper personal protective equipment (PPE), including N95 masks,” she told Al Jazeera.
Is airborne COVID-19 less contagious?
The extent to which the coronavirus can be spread by the aerosol route – as opposed to by larger droplets – remains disputed.
While the WHO has long maintained that the primary source of infection is through droplet transmission, it has acknowledged there was “emerging evidence” of airborne transmission.
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“The possibility of airborne transmission in public settings – especially in very specific conditions, crowded, closed, poorly ventilated settings that have been described, cannot be ruled out,” Benedetta Allegranzi, the WHO’s technical lead for infection prevention and control, said in a news briefing this week.
This came after a group of 239 scientists from 32 countries and a variety of fields made the case in an open letter that there was a “real risk” of airborne transmission, especially in indoor, enclosed and crowded environments without proper ventilation.
Dancer, who was one of the signatories of the letter, said there is a lower risk of catching the virus the further you are from the source.
Jose-Luis Jimenez, a chemist at the University of Colorado, also told Al Jazeera the “virus loses infectivity over a period of an hour or so indoors”.
How can you protect yourself?
Wearing face masks properly and maintaining physical distancing are recommended at all times.
Experts also recommend avoiding crowded places, especially public transport and public buildings.
In closed spaces at schools, offices and hospitals, increasing proper ventilation with outdoor air by opening windows can also mitigate the risk of infection, Jimenez said.
“For spaces where ventilation cannot be increased, we recommend portable high-efficiency particulate air (HEPA) filter air cleaners or possibly ultraviolet (UV) germicidal lights at the high end of need. We do not recommend other types of air cleaners.”
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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