Medical professionals: This is new information, no? My layman’s understanding was that, until now, scientists believed that the virus’s different strains weren’t meaningfully different from each other, which is why they were optimistic that a vaccine would have long-lasting effect. We could vaccinate against the baseline virus and be confident that it would confer immunity against COVID’s many distinct mutations.

Now here comes a Chinese study challenging the conventional wisdom. If you use basic techniques to distinguish one strain from another then yes, they all look more or less alike. But if you use “ultra-deep” genome sequencing, you begin to see subtle differences with potentially momentous consequences.

We’ve spent weeks spitballing theories for why New York has been hit so much harder than the rest of the country. It’s the density! Or it’s the subway. Or maybe it’s something genetic among the ethnic populations that have suffered most. But what if it’s as simple as New York having been hit by a strain of the disease that’s deadlier than the strain(s) circulating throughout the rest of America?

Li took an unusual approach to investigate the virus mutation. She analysed the viral strains isolated from 11 randomly chosen Covid-19 patients from Hangzhou in the eastern province of Zhejiang, and then tested how efficiently they could infect and kill cells.

The deadliest mutations in the Zhejiang patients had also been found in most patients across Europe, while the milder strains were the predominant varieties found in parts of the United States, such as Washington state, according to their paper…

They found some of these mutations could lead to functional changes in the virus’ spike protein, a unique structure over the viral envelope enabling the coronavirus to bind with human cells. Computer simulation predicted that these mutations would increase its infectivity.

To verify the theory, Li and colleagues infected cells with strains carrying different mutations. The most aggressive strains could generate 270 times as much viral load as the weakest type. These strains also killed the cells the fastest.

Where did the most common strain in New York arrive from? Right, Europe. The region with the most deadly outbreaks in the world, at least if you believe China’s numbers.

But that’s one implication of this finding. Even if we believe that China’s cooking the books, it’s conceivable that the early strain that spread in Wuhan was less deadly than later mutations in other countries. Which would be ominous, as it would leave us to wonder how much more deadly the virus might get as it continues to mutate.

Knowing that some regional strains are deadlier than others would also create some knotty questions in the U.S. about interstate travel. If all four corners of America are dealing with the same basic disease then limiting travel matters less. We don’t want people from hot spots visiting less affected regions and seeding outbreaks, of course, but hot spots like New York are already cooling off and will hopefully see cases shrink to a minimum in a month or two. However, if the New York strain is considerably more dangerous than other regional strains then maybe we don’t New Yorkers traveling anywhere. Even if they’re no more contagious than people in other regions, they may be carrying something with outsized effects on mortality.

Another implication: Does the Chinese study help explain why tests are so inaccurate?

My oncologist suggested to me on Saturday that the mutations might be accounting for the ~30% false negatives they are getting. pic.twitter.com/pWKfuVqlkF

— @changingourmindset (@changermindset) April 21, 2020

Is it possible that some strains of the virus have diverged from each other so much that a diagnostic test targeting one would fail to detect another?

Another ominous possibility:

On a long enough time horizon, they could perhaps allow for reinfection as well.

This is not a short-term problem, but it may be a long-term one given the massive volume of cases at this point.

Things change when you give it a million case-years to evolve instead of a thousand.

— ice9 (@__ice9) April 21, 2020

If you’re infected by one strain of the virus, are the antibodies left in your system effective against other strains? That’s really a variation of the vaccine question posed up top.

There may be a major silver lining to the theory that different strains have wildly different effects, though:

If this is true, it would be easy to develop an attenuated vaccine for SARS-2 by selecting a strain with low pathogenicity but decent immunogenicity.

— PharmaHeretic (@Pharmaheretic) April 20, 2020

Find a strain of the virus that produces few symptoms but triggers enough antibodies to fend off more deadly strains of the disease and you have an effective partial vaccine. As strange as the thought of “pox parties” are for COVID, they’d be worth it if you knew that the version of the disease you were infected with had far more upside than downside risk.

Seems like the first step in figuring out if the Chinese study is correct would be to sequence different strains around the country in a basic way and see which ones have higher concentrations of the New York/Europe strain and which don’t. Is the strain more common in areas where deaths and hospitalizations are higher? If so, what do we do about isolating those regions — and controlling travel from Europe, since we won’t want anyone importing that strain once we’ve contained it here? It’s conceivable that we’d have more to fear from travel from NATO countries than we do from China.

One thing that doesn’t seem likely, though, is that different strains account for why some people are asymptomatic and others aren’t. You’d expect an insular population in which lots of people are infected would be spreading the same strain among themselves, not a variety of different ones, leaving the reason for why some get sick and some don’t unclear. Plus, even if it turns out to be true that some strains are more or less likely to produce asymptomatic cases, it may not be the case that deadlier European strains are in the “less likely” category. Remember that the study I highlighted last night of a town in Italy, one of the hottest hot spots on Earth, found 43 percent of people who tested positive were asymptomatic. The question of why so many people don’t have symptoms even in areas where the disease is notably deadly remains a mystery.