Why would isolated Eskimos get colds?

Welcome to cold and flu season, especially for those of you with kids in school.

The prevailing wisdom about colds is that the virus is passed from person to person, right? “Why can’t we cure the common cold?” (Guardian, 2017, about “a breakthrough”):

The only failsafe means of avoiding a cold is to live in complete isolation from the rest of humanity.

Eskimos in the pre-machine age came pretty close this “complete isolation” and yet, in The North-West Passage Roald Amundsen reported from Gjöa Haven, about as isolated as humans can be:

The return of the Eskimo again imparted a lively and variegated aspect to our little harbour. They came on board, as a rule, generally of an evening in great crowds to visit us or to introduce new friends. They were always gay and happy, and we became very good friends with them. It has always been believed that the air in the Polar regions is absolutely pure and free from bacilli; this, however, is, to say the least, doubtful, in any case as far as the regions around King William Land are concerned, for here the Eskimo nearly every winter were visited with quite an epidemic of colds. Some of them had such violent attacks that I was even afraid of inflammation of the lungs, and as nearly every one of them contracted the illness, it must in all probability have been occasioned by infection. Happily those on board the “Gjöa” escaped, but we certainly took due precautions. We had great trouble to put a stop to the spitting habit. The Eskimo are very bad in this respect, but when we had them some time under treatment they improved and paid more attention to our prohibition.

A bit later in the same book:

Summer is, one may say, rapidly succeeded by winter; the lakes freeze over, and the snow falls; but with the Eskimo there is a short period which may be described as their autumn, and as their most dismal season, just before the ice is thick enough to be used as building material. Superstition prevents them from lighting fires indoors. Their homes are, therefore, miserable in the temperature which then prevails, and they live in a raw cold, damp atmosphere, in which all, without exception, contract severe colds.

There was some travel among Eskimo communities back then, of course, but it often took so long that people would have gotten over their colds by the time they showed up at the destination settlement.

Related:

• “Respiratory virus antibodies in sera of persons living in isolated communities” found that “the results differed little from those for non-isolated communities”