Last week, the American CDC released revised guidelines for reducing infections of coronavirus post-lockdowns. It’s much of what we’ve heard before: Wear your mask, wash your hands, and “in general,” they write, “the more closely you interact with others and the longer that interaction, the higher the risk of COVID-19 spread”. What many are still wondering though – and what there’s still alarmingly little information about – is what’s the deal with asymptomatic COVID-19 cases?
Considering Asymptomatic cases when calculating public health risk
According to a World Health Organisation representative there is “extremely abundant” evidence that even without any symptoms, you can still spread COVID-19. This is extremely important for lawmakers to consider when making decisions about how to mitigate the spread of the virus. It’s also something that warrants considering when we decide whether or not to go out after lockdowns are relaxed. Not all people who are shedding the virus without showing symptoms, though, can actually be classified as “asymptomatic”.
“There’s a difference between people who never develop symptoms and people who just don’t have them yet,” writes Gregory Barber for Wired, “and that matters when calculating public health risk”.
It’s been hard for researchers to identify exactly what percentage of carriers are asymptomatic, never mind determine the impact they have on the spread of the virus, and thus it’s been hard for individuals to find clear information about it and stay informed. The mechanisms by which asymptomatic patients, or “silent spreaders” share the virus with others has thus far remained pretty unclear.
Then there are those who become infected and have yet to show signs of infection (but who will later). These carriers are referred to as “presymptomatic” and are, in general, a lot easier to study for the very fact hat they do later show signs of being sick. Symptoms, on average, take between five and 14 days to appear, and even then may – if you’re lucky – be very mild (excluding the potential permanent damage that comes with this virus, that is).
* @WHO guidance on asymptomatic #SARSCoV2 transmission is confusing due to poor health communication. Public won't be able to make fine distinctions between 1) asymptomatic (never develop symptoms); 2) pre-symptomatic (who go on to get symptoms); & 3) mild or atypical symptoms.
— Lawrence Gostin (@LawrenceGostin) June 9, 2020
Lois Parshly for Vox cites a study that found that a terrifying 40-45% of infections may, in fact, be asymptomatic. This in turn means that almost half of those infected may be walking around assuming they aren’t sick, and passing the infection on to others who then could develop serious symptoms – a terrifying thought. Other studies show that this number could be as high as 80%, or even as low as 6%. So, who really knows.
Regardless of all that uncertainy, David Shukman writing for the BBC, says that asymptomatic “silent spreaders” may be driving the pandemic, keeping it spreading despite public health measures.
Being asymptomatic doesn’t mean you’re unaffected.
While it may seem that being asymptomatic means the disease doesn’t affect you, that’s not exactly the case. Parshly quotes Eric Topol, a research methods expert and director of the Scripps Research Translational Institute, who says that two noteworthy conclusions can be drawn from recent research. One is that “you can be infected with, and even have a lung injury from, COVID-19 without knowing it”.
Topol refers to other studies coming out of South Korea and the Diamond Princess cruise ship, which found substantial abnormalities in the lung scans of asymptomatic people.“That tells you something is going on, even in people who aren’t aware of it,” he told Parshly. “It suggests the possibility that you may be asymptomatic and have lingering damage or injury on a chronic basis”.
Additionally, The studies showed that the viral load of asymptomatic patients was very similar to that of presymptomatic patients, though even that still feels unclear. It’s suspected that patients may be the most contagious when they’re presymptomatic – going to develop symptoms, but not yet noticing they’re sick. Shukman cites a study which mentions a “critical period of 24-to-48 hours before the visible onset of the disease in which people can be highly infectious, perhaps even their most infectious”.
“When researchers have followed people who were initially classified as asymptomatic, they’ve often found they developed symptoms later on,” writes Barber. “There’s also an issue called ‘recall bias’—people are less likely to remember that they experienced mild symptoms than severe ones”. Not to mention, the symptoms of COVID-19 vary so much, that they often don’t match what’s expected, and patients may be improperly labelled as asymptomatic or even assume they’re not sick at all.
“There’s a lot of jargon out there and it’s even confusing to scientists,” Ashleigh Tuite, an epidemiologist at the University of Toronto, told Barber. When that jargon is introduced into a politicised environment –or worse, Twitter feeds – it can become distorted and confusing.
Why does the difference between asymptomatic and presymptomatic matter?
Really, it doesn’t.
The only thing we really need to take a way from this conversation is the fact that in order to stop the spread of the virus, we all need to behave as if we are asymptomatic or presymptomatic. We need to take all the steps we would if we were sure we had been infected.
Parshly writes that “in many ways, this whole conversation is a distraction from the key actions we know we need to be taking now. Since you may already be sick but don’t know it yet, it’s important to avoid exposing others by social distancing, wearing masks, and washing your hands. If you may be sick and infecting others without ever knowing it, it’s equally important to take the same steps.”
Shukman echoes these sentiments by stating that “as lockdown measures are eased and more people start to use public transport, return to work or go shopping, getting to grips with the invisible risk matters more than ever. At the moment, there is no way of telling who among the growing crowds may be carrying the virus without knowing”.
The problem now is that “there’s clearly an amount of fatigue and a desire to return to life as normal,” Barber quotes Tuite. “And with that, there is a sense of invulnerability among younger people.”
Just because we’re tired of coronavirus, doesn’t mean it’s gone away, and with all we’re learning about how it spread, it seems now’s not the time to let our guard down.