Where all these new COVID cases are coming from

As BC experiences its most dramatic spike in cases since the onset of the pandemic, health officials are now starting to consider a renewed suite of lockdown measures, including a 14-day quarantine period for new arrivals to Vancouver Island. Below, Capital Daily science writer Harley Gordon provides some perspective on where these new cases are coming from and how to avoid them.

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COVID-19 is more contagious than the flu, but luckily less contagious than measles. While this pandemic has featured a lot of focus on surfaces (doorknobs, furniture and hand railings) these are fortunately a minor risk of infection.

Where COVID-19 is most successful at spreading is when you are near enough to be hit with respiratory droplets from an infected person. Playing board games, watching a movie; anything that puts you in close proximity with someone else for an extended period (think 10 minutes or more) is going to be a high-risk situation.

However, the environment you are in plays a key role in determining your risk of catching COVID-19 from a nearby carrier of the virus. If you are outside the UV light from the sun can kill the virus in as little as 10 minutes. Similarly, if you are in a well ventilated place where the air is exchanged often, the risk of exposure goes down. Airplane cabins, for example, have a full air exchange every two minutes, which is about twice as often as a hospital operating room or eight times more than a typical family home. This is why Canada’s Chief Public Health Officer Dr. Theresa Tam spoke last week on the relative low-risk of air travel.

Sometimes, particles of COVID-19 can be released in an aerosolized form, meaning the droplets are so small that they linger in the air for minutes or more — something that is referred to as the virus being “airborne.” Though rare, these airborne droplets can be a source of COVID-19 infection, and they’re of particular concern because they can travel further than two meters.

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Family gatherings, private parties and returning to work indoors are among the highest risk activities for catching COVID-19; basically, any situation that is going to have people in close quarters sharing the same air as a carrier of the virus.

One of the most preventable spreading events in BC was a single gym in Surrey that was the cause of 43 infections. According to the gym's social media, several patrons who happened to be COVID-19 positive attended the gym while awaiting their test results — a direct violation of public health orders which mandate self-isolation for anyone awaiting test results.

In another case, a COVID-19 positive wedding guest spread the infection to 15 other people, causing 3 hospitalizations, 1 death and an outbreak at a long-term care home. Similarly, just one infected individual at a fitness class resulted in more than 200 new infections, 6 school exposures, and 3 hospitalizations.

Viral growth is exponential, and these cases indicate just how quickly a single infection can spread.

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Going to restaurants and grocery shopping are not significant sources of COVID-19 infections, at least according to the latest numbers posted by the BC Center for Disease Control. It is the spread within households that account for a bulk of new infections.

This is one of the primary reasons that Provincial Health Officer Bonnie Henry has declined to institute a compulsory public mask mandate, with the reasoning that it wouldn’t target homes, where most of the spread is occurring. “Right now, we are seeing rapid transmission in social gatherings where masks would not be worn anyway,” she wrote in a recent op-ed. The public health orders limiting household gatherings to six people while still allowing indoor dining at restaurants may seem paradoxical, but is simply trying to target infections where they are occurring.

Unfortunately though, the province is not always able to identify how people have gotten infected. About a fifth of all BC’s COVID-19 cases come from an unknown source, with that rate rising to half for individuals aged 20-29, around half of all COVID-19 cases come from an unknown or unnamed source.

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With record setting cases nearly every day it seems as the whole province is exploding with new cases. However, the pandemic is still very localized. Surrey has the most cases in the province at nearly 4,000 cases per 100,000 residents; meaning that more than 4% of Surrey either had or currently has COVID-19. Greater Victoria has only 63 cases per 100,000 inhabitants, equivalent to only 0.06% of the population. Although Vancouver Island cases continue to rise, their growth is not near the levels seen in the Fraser Valley. Vancouver Island remains the safest health region in the province, with almost all new cases here originating from someone who has recently travelled to the Fraser Valley. Even the Nanaimo hospital outbreak last Wednesday was caused by someone returning to work after visiting the Fraser Valley.

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It’s no surprise that jobs in healthcare are at some of the highest risk for catching COVID-19. Specifically, nurses and other care workers account for 40% of cases among healthcare staff. While this pandemic began with healthcare workers representing a third of all BC cases, they now represent just 6% of COVID-19 cases in the province.

Working in a factory or manufacturing line is also risky, with long indoor shifts and prolonged contact with other people increasing the risk of viral transmission. Just this Saturday, an outbreak at a health-food manufacturing plant in Port Coquitlam may have caused the youngest COVID-19 death in the province at only 30 years of age. Meat packing plants, where workers often work on large assembly lines within close proximity to each other are also high risk, last month Surrey saw an outbreak at a beef processing facility that led to 13 new cases.

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In September, when 2,000 British Columbians were tested for COVID-19 antibodies, 19 people tested positive, indicating that they had already contracted and recovered from the virus. Extrapolating the results means around 1% of BC may already have some immunity to COVID-19, meaning we’re still a long way off from herd-immunity.

At the current rate of new infections, the BC Centre for Disease Control has calculated that new cases are doubling every 13 days. If the rate of infection is not reduced, by the end of November we could be seeing upwards of 1,200 daily new cases.

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Critical care beds in BC are not overflowing with patients yet. Throughout the province there are 767 critical care beds. Right now, half of them remain available and only about 7% of them are currently occupied by COVID-19 patients. Health authorities can handle more cases, but there are limits, particularly in regions with limited capacity. In the Vancouver Island Health Authority, for instance, there are only 97 critical care beds, over half of which are currently occupied with non-COVID-19 patients. Using a critical care rate of 1% for COVID-19 (roughly 50 ICU patients per 5,000 COVID-19 cases) It would only take 5,000 active cases of COVID-19 on the island to overwhelm the system. This might seem far off, but with exponential growth and the potential to see thousands of new cases daily, this is a real concern.