Chart of the Day: Why Is COVID-19 Worse In Some Parts of the World and Better in Others?

Here is something tentative but genuinely fascinating. I promise the payoff is worth it, but first it’s going to require a little bit of background about how the immune system works.

Human cells all contain proteins called human leukocyte antigens, or HLAs, which swim around and periodically latch on to invading viruses, which they bring to the surface of the cell. White blood cells, patrolling outside the cells, are always looking for stuff that doesn’t belong, and if an HLA presents an invader to the surface of the cell white blood cells immediately attack and destroy the entire cell. Conversely, if no HLA brings a virus to the surface, then its existence goes undetected and the immune system can’t attack it.

Now here’s the interesting part: there are dozens of different kinds of HLAs, and everybody has a different HLA profile. That’s one reason that if you and I both get sneezed on by someone with a cold, one of us might get sick while the other doesn’t. It means that one of us happened to have the right HLA to latch onto the virus while the other one didn’t.

And here’s the even more interesting part: different human populations have different average HLA profiles. This means that some populations are more resistant to certain diseases than others. For example, COVID-19.

In a recent paper, a team of researchers looked at 140 different HLAs, and in particular discovered that COVID-19 seemed to be sensitive to the ratio of the S and N types. Here’s the chart:

One of the great mysteries of COVID-19 is why China has been relatively unscathed. Aside from the initial outbreak in Wuhan, there have been hardly any cases in the entire country. But how can that be? Even with strong quarantine procedures, it’s simply not plausible that a fairly transmissible virus like COVID-19 could fail to spread widely in a country of over a billion people.

HLAs might be the answer. As you can see in the chart, the authors estimate that the S/N ratio for China is about 5.7, one of the highest in the world. That would suggest high resistance to the COVID-19 virus. At the other end, Sweden has an S/N ratio of 3.8, one of the lowest in the world. It’s possible that the “Swedish experiment” was never an experiment at all. They might have been doomed to a high COVID-19 infection rate no matter what they had done.

This is very preliminary research, and HLA profiles are certainly not the entire story. That said, if this is confirmed—or if other HLA profiles are identified that are associated with COVID-19—it might change our understanding of why infection rates are very different in different parts of the world.

TIME IS RUNNING OUT!

We have an ambitious $350,000 online fundraising goal this month and it's truly crunch time: About 15 percent of our yearly online giving usually comes in during the final week of the year, and in "No Cute Headlines or Manipulative BS," we explain why we simply can't afford to come up short right now.

The bottom line: Corporations and powerful people with deep pockets will never sustain the type of journalism Mother Jones exists to do. And advertising or profit-driven ownership groups will never make time-intensive, in-depth reporting viable.

That's why donations big and small make up 74 percent of our budget this year. There is no backup to keep us going, no alternate revenue source, no secret benefactor. If readers don’t donate, we won’t be here. It's that simple.

And if you can help us out with a donation right now, all online gifts will be matched thanks to an incredibly generous matching gift pledge.

payment methods

TIME IS RUNNING OUT!

We have an ambitious $350,000 online fundraising goal this month and it's truly crunch time: About 15 percent of our yearly online giving usually comes in during the final week of the year, and in "No Cute Headlines or Manipulative BS," we explain why we simply can't afford to come up short right now.

The bottom line: Corporations and powerful people with deep pockets will never sustain the type of journalism Mother Jones exists to do. And advertising or profit-driven ownership groups will never make time-intensive, in-depth reporting viable.

That's why donations big and small make up 74 percent of our budget this year. There is no backup to keep us going, no alternate revenue source, no secret benefactor. If readers don’t donate, we won’t be here. It's that simple.

And if you can help us out with a donation right now, all online gifts will be matched thanks to an incredibly generous matching gift pledge.

payment methods

We Recommend

Latest

Sign up for our free newsletter

Subscribe to the Mother Jones Daily to have our top stories delivered directly to your inbox.

Get our award-winning magazine

Save big on a full year of investigations, ideas, and insights.

Subscribe

Support our journalism

Help Mother Jones' reporters dig deep with a tax-deductible donation.

Donate