I want to draw your attention to this interesting article at the New York Times by epidemiologist Marc Lipsitch, considering who is likely to contract SARS-CoV-2:
The ideal scenario — once infected, a person is completely immune for life — is correct for a number of infections. The Danish physician Peter Panum famously figured this out for measles when he visited the Faroe Islands (between Scotland and Iceland) during an outbreak in 1846 and found that residents over 65 who had been alive during a previous outbreak in 1781 were protected. This striking observation helped launch the fields of immunology and epidemiology — and ever since, as in many other disciplines, the scientific community has learned that often things are more complicated.
One example of “more complicated†is immunity to coronaviruses, a large group of viruses that sometimes jump from animal hosts to humans: SARS-CoV-2 is the third major coronavirus epidemic to affect humans in recent times, after the SARS outbreak of 2002-3 and the MERS outbreak that started in 2012.
Much of our understanding of coronavirus immunity comes not from SARS or MERS, which have infected comparatively small numbers of people, but from the coronaviruses that spread every year causing respiratory infections ranging from a common cold to pneumonia. In two separate studies, researchers infected human volunteers with a seasonal coronavirus and about a year later inoculated them with the same or a similar virus to observe whether they had acquired immunity.
In the first study, researchers selected 18 volunteers who developed colds after they were inoculated — or “challenged,†as the term goes — with one strain of coronavirus in 1977 or 1978. Six of the subjects were re-challenged a year later with the same strain, and none was infected, presumably thanks to protection acquired with their immune response to the first infection. The other 12 volunteers were exposed to a slightly different strain of coronavirus a year later, and their protection to that was only partial.
It is presently hoped that some people have acquired at least temporary immunity to the virus. Or that some people are resistant to the infection because they have contracted a similar disease in the past.
There is also a certain amount of information emerging that some people are more predisposed to becoming infected or if infected seriously ill, not just by virtue of pre-existing health conditions or behavior but by their genetic makeup. To some extent such research is taboo in our society not only because it violates notions of “fairness” but because it has been abused in the past. That’s an unfortunate but understandable prejudice. The greater our knowledge about this virus, the greater may be our ability to fight it.
Read the whole thing.
It doesn’t appear that the genetic study tagged the names of the countries, but from one of references, other than to note that “two Asian countries which were initially severely hit by the virus, China and Korea, are also characterized by low D allele frequencies.”
Looking elsewhere, I found “The frequency of the D allele seems to follow a clinal distribution, being highest among Africans and Arabs (0.70–0.60), followed by Caucasians (0.46–0.58), then the Japanese (0.33–0.35) and the Chinese (0.29). The Yanomami Indians and Samoans seem to have the lowest frequencies: 0.15 and 0.09, respectively.”
I’m not sure it would be surprising that the population in which the virus originated would tend to have greater predispositions to infection. Also, these ethnic groups tend to resemble the blood types that are showing a relationship in China and New York.
It may be just a coincidence but Italy is one of the places that has a high prevalence of the sickle cell gene. It used to be mostly in Sicily and Southern Italy but is now throughout Italy.
Watch out for COVID-19 virulence among native-born Sardinians and their descendants. They also developed Thalassemial resistance to Malaria, which when recessively inherited can cause some pretty nasty auto-immune diseases. A lot of Sardinians also live to some pretty ripe ages as well, although I believe some of that may have been due to falsification of papers to avoid being drafted by Mussolini in WWII.
A reminder that it is the North of Italy that was hit, the South has been (relatively) spared so far. It also doesn’t explain France, Spain, UK, Belgium, Netherlands, Turkey which all have bad outbreaks.
The only thing I could think of in common for these countries is they belonged to the Roman Empire.