Piecing together the picture of a virus
A tour of the latest additions to a half-finished puzzle.
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The Worldwise View
For the past few weeks I’ve been keeping an eye on new information about the coronavirus.
The puzzle has a lot of missing pieces, and the science that’s going to put it all together is incremental.
But bits of the picture are starting to emerge. Six months into the year, the New York Times published its round-up of what’s known and what’s still elusive about SARS-CoV-2.
I’ve pieced together what follows from various sources, and the tour starts with insights that have a bearing on how countries manage their pandemic policies from this point on.
Refined responses
On cue with the NYT, Axios published its own mid-year summary of key learnings from what it called the first wave of the pandemic.
What caught my eye was the mention of potentially more targeted, risk-based versions of lockdown that could follow the blunt versions we saw for the first few months—an idea that first emerged in late May and was highlighted in this earlier post.
It’s based on two concepts: the ‘K number’, and ‘superspreaders’. Below is a brief explainer—or skip it to get to the gist.
The ‘K number’ is a measure that allows scientists to analyse clusters of cases—this is a nice and simple explainer by the Guardian. So far, the scientific guidance on public health policy has been based on a different measure, the ‘R value’, which describes the average number of infections caused by a single patient. But the K number could turn out to be more important.
The related concept of ‘superspreaders’ describes a small percentage of people who are responsible for a large number of infections. According to Axios, “roughly 10% of COVID-19 cases appear to have caused around 80% of new infections”. What makes a superspreader is more about circumstance than biology (NYT + Wired UK).
Along with the K number, the notion of superspreaders is getting attention for its potential to help put a finer grain on restrictions, for example through policies that focus on high-risk events or groups of people.
Exactly what that looks like in the real world is still unclear. I’m not sure reopening pubs is it though!
A more nuanced version of future lockdowns might come in the form of ‘social bubbles’ (Nature + MIT Tech Review). 'Rolling lockdowns' have been proposed too. Public health specialists have argued that another way to refine the response and focus resources is to use emerging data on who is more susceptible.
There’s more on that susceptibility below—first, a look at new evidence on how the virus spreads.
Discord over air travel
A couple of weeks ago the Wall Street Journal reported that there's a consensus emerging over how people are more likely to catch the virus: in crowded events, poorly ventilated areas and places where there’s loud talking or singing. It raises the question of how risky it is to travel by airplane. Or go to the pub.
That’s all linked to how the virus travels in the air, which is the latest scientific point of discord. Experts from 32 countries have said they believe the virus lingers in the air indoors and stays infectious—but the WHO says this isn't clear yet, and that airborne spread is limited to certain cases like medical procedures.
It’s not the only instance where the agency has been at odds with the wider scientific community. In early June it said it's rare that people infected but without symptoms will pass on the virus to others—a statement that was followed by widely reported backtracking and confusion (Washington Post + Guardian + Forbes + NPR).
It led to a New York Times report asking if this is part of a pattern where the WHO’s advice is lagging behind the latest evidence.
Although the label 'asymptomatic' is still a bit fuzzy, the consensus seems to be that up to half of the people infected with the virus are completely unaware of it. And this boosts the case for tracing contacts and wearing facemasks—the latter being another sore point of science-based advice (Reuters + Washington Post).
A couple of other lingering question marks that got some coverage:
No one really knows what a safe distance is—but there’s some evidence that your risk doubles if you stand one metre apart from another person instead of two. And could a mutation be making the virus more infectious? Or could it be burning out after 20% of a population is infected?
Photo by Fusion Medical Animation on Unsplash
On immunity, and who’s susceptible
Herd immunity is complicated. And the evidence on whether we’re getting there isn’t very encouraging.
This piece in the Conversation gives a succinct explanation of why herd immunity looks less and less like an answer: essentially, immunity levels are far lower than what’s needed to protect communities, even in Sweden where the virus has been circulating more freely. Some evidence suggests antibodies only last for 2-3 months.
It’s worth noting that immunity isn’t all about antibodies—other immune responses could also be useful.
Meanwhile, more clues are emerging as to why some people may be more vulnerable to severe Covid-19. One is having type-A blood. The US health agency has said that patients with underlying conditions are 12 times more likely to die of the disease as otherwise healthy people. But could race be more important than pre-existing diseases for the risk of dying?
In the US, pregnant women have now been added to the list of high-risk groups.
There’s some fresh evidence on the Covid-related inflammatory disease reported in children. Studies suggest the syndrome is new and distinct from Kawasaki disease. It could be an inflammatory response triggered by immune response—and if that proves to be the case, it may be a problem when it comes to vaccination. But there’s a lot that’s still unknown. The reported cases stand at around 300 globally.
Finally, could vitamin D having a protective effect?
In Quotes
What's behind the gender gap? "When in doubt, look to social factors first, not biology"—Heather Shattuck-Heidorn, Meredith W. Reiches and Sarah S. Richardson writing in the NYT about the gender gap in Covid-19 deaths
How the virus hits the body
More and more reports are focusing on how long the disease lingers for some people (Atlantic + New Scientist). The long-term effects of Covid-19 resemble a fatigue syndrome, even for mild cases.
A report from Scientific American takes a closer look at how the virus works. And the Economist has a very thorough account of what science and medicine tells us about how it attacks the body. An interesting piece in the Washington Post lays out what we've learned from autopsies.
Other reports outline the serious damage coronavirus inflicts on the lungs. There’s also evidence that it doesn’t just attack the respiratory system. It may cause brain complications, and damage to the nervous system has been involved in some deaths of fairly young patients. It may also trigger diabetes.
This piece explains how the virus short-circuits the immune system, and this one goes into why some people lose their sense of smell after infection.
One more thing
It could take more than a decade of scientific work to settle the question of how the coronavirus jumped to humans - Nature
But the idea that the virus emerged from a Chinese lab isn't going away, despite scientific consensus against it - Telegraph
Worldwise is written by Anita Makri. Was this email forwarded to you? Learn more and subscribe here.