This is the fifth post of a re-run of our Transmission Riddle series, which was originally posted in 2022. Each post has been updated and reworked with what new evidence we could find. The serial numbers of the original posts may not correspond as we expand, merge, edit and add, like a concertina. Because of content transmission, riddles are looked at in the context of isolation, making this the 9th post in the Architecture of Isolation series.

Thanks to our reader, John Davison, this post is where Riddles and Isolation come together. John asked us to explain “the Seattle and Argentinian trawlermen”. No references were provided, but Carl’s radar picked this July 2020 story up.

In a nutshell, 61 crew members who had been quarantined for two weeks before sailing and all tested negative for SARS-CoV-2 at the end of isolation. They set sail for the Antarctic fishing grounds in their trawler. After about 35 days at sea with no contact (other than with the fish), they started exhibiting signs and symptoms of Covid and were quickly returned to base in Tierra del Fuego. All but a few were positive, and two were hospitalised.

This is amazing! How can that be? Do we have carriers no one knows about?

Attentive readers of the first Riddle series will recall our mentioning similar episodes, and indeed, the two series are called “Riddles” and “Isolation”.

Apparently, nonsensical events such as the trawler story have been known for centuries. The name “influenza” comes from the Italian “Influenza degli astri” (influence of the planets). Our ancestors were as bewildered as our Mr Davison. It comes and goes without rhyme or reason; surely, the planets must be causing all this mayhem! 

To put recent knowledge about the riddle into its historical context, we offer you this narrative by Sir Christopher Andrewes from his book “The Common Cold” and the chapter “Transmission vs Activation”. Andrewes was no empty vessel; he was part of the trio who isolated the first human influenza virus.

“It is well-established that polar explorers and others cut off from contact with their fellow men for some time are abnormally susceptible to catching colds when they once more rejoin civilization. This matter will be discussed more fully in Chapter 15. Could we possibly get hold of such returning hyper-susceptible explorers and carry out our contact experiments on them? Alas, we could not. Returning explorers show a not unnatural interest in rejoining their families. We planned therefore to keep the whole thing under our own control by marooning our own party of explorers on our own desert island. 

We learnt through Dr Fraser Darling of a suitable island, Eilean nan Ron, lying one and half miles off the little port of Skerray on the north coast of Sutherland. It was just over a mile long and less than a mile wide surrounded by fairly steep cliffs but with one good landing place. The island had a number of well-built houses on it but had been abandoned by the inhabitants for economic reasons twelve years earlier. It be­longed to the Duke of Sutherland who kindly lent it to us. A few of the houses were readily made habitable and early in July 1950 a party of twelve volunteers was, not unwillingly, marooned on the island. Most of them were students from the University of Aberdeen; in charge was an ex-superintendent of police. They were to be there for three months, their summer vacation, the longest period for which we could readily obtain volunteers. They took with them all the stores and equipment they needed for their stay; and they also had a small radio transmitter and receiver with which they maintained daily con­tact with the mainland.

One man had a cold on arrival, July 8th; another case occurred on July 9th and three more on July 11th. There were no more until the isolation ended on September 19th. On that day a colleague and I landed and made contact with some of the Party to see whether any stranger, even without a cold, could introduce infection. 

Nothing having happened, another of our team arrived with five others; all had just been inoculated in Aberdeen with one of our “pedigree” colds, that is one which had been studied for some while at Salisbury [MRC Common Cold Unit]. Meanwhile the island had been divided into three, each third inhabited by a party of four islanders, who kept apart from the other two parties. Each group was exposed under different conditions to the newly arrived party, each of whom had either developed a cold already, or did so very shortly after landing. The 'colds' had arrived late in the day, but as early colds are probably the most infectious we carried out the experiment forthwith and far into the night. It was a fine night and a magnificent display of the Aurora·Borealis made the whole thing most romantic. The six invaders with colds attempted to infect the islanders in one of three ways. They occupied a room in one of the houses for three hours in the absence of the four 'natives' (party A). To quote the report: “During their occupation they were liberal in the way they disseminated nasal discharge on playing cards, books,·cutlery and handles of cups, letters, chairs, door-handles and tables”. They then left the room, which was aired for half­ an-hour before party A entered. The invaders then occupied a room with party B, being separated from them by a blanket stretched across the room but not quite reaching floor or ceiling. This arrangement was intended, and in fact shown by appropriate tests, to permit droplet nuclei to pass to the opposite half of the room while stopping coarse particles. Party C lived and ate with·the people with the colds for three days, allowing maximum exposure. To our intense surprise and dis­appointment, no colds developed in any of the groups. Four more people with colds arrived a few days later and were exposed to party A under conditions of 'maximum exposure'. Again no colds developed.

We then learnt, through our radio, of a crofter on the main­ land who had a cold, though not a very early, streaming one. He was exposed to Party B, talking round a fire for two periods of two hours, and this time transfer was successful, three of four of the Bs developing colds within a few days.  

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In reviewing the rest we inclined to think at the time that our 'pedigree' cold strain was for some reason less effective than a naturally occurring one. In the light of later work on the multiplicity of strains of cold-viruses it seems far more likely that the islanders were resistant as a result of the little outbreak of colds a few days after their isolation began; and that by bad luck this was due to a virus of the same type as the pedigree virus used in the later test.

Though this laborious experiment failed in its main objective, it gave us some useful ideas for future work.”

The year was 1950, and Sir Christopher blamed immunity for the failure of his elaborate experiment of isolation and subsequent exposure. The “pedigree” was almost certainly rhinovirus, although its identification came later. Other experiments of transmission also gave equivocal results.

Up until the 1930s, apparent outbreaks of influenza-like illness in isolation settings were recorded in a haphazard way so we may dismiss them as folklore. 

However we now offer you a very well-documented historical example reported in the Journal of Hygiene (London). This one, too, is from a chilly environment: Antarctica.

From March 18, 1969, to December, 12 men wintered at the Adelaide Winter base when the first aircraft arrived. Six of the 12 sequentially developed symptoms and signs of a common cold after 17 weeks of complete isolation. 

No specimen, both swabs, cultures or sera, revealed exposure to a causative agent. The outbreak was studied in collaboration with Andrewes’s MRC Common Cold Unit, which ran an extensive range of tests looking for the usual agents, including coronaviridae. The recording was carried out under radio supervision by a trained physician at the base and included the recording of symptoms and meteorological and environmental conditions.

And history seemingly repeats itself. What you make of this timeline?

The unclear role of isolation has been studied extensively, with perhaps the best-known example being the 1933 study by the aptly named Drs Paul and Freese. They showed that in the Spitsbergen Islands, colds died down at the end of the trading season and were reintroduced when sailing conditions allowed ships to berth again. The first to go down with a cold was usually the harbour storekeeper, the fellow who had the most contact with the incoming sailors.

So, the Spitzbergen narrative is wholly in keeping with germ theory and our contemporary understanding of immunity and transmission. But what of the Eilean nan Ron, trawler and Antarctica episodes?

Are influenza-like illnesses partly not infectious? Were the samples wrongly harvested? Do the records lie? Do respiratory viruses live with us and activate when the time comes? If so, how do we explain the worldwide presence of genetically identical viruses and their near synchronous appearance thousands of miles across? 

So many questions and uncertainties persist. However, we leave this post with yet another riddle from the great Spanish Influenza of 1918-19. 

In 1919, the following observations were made in the BMJ by Dr Andrew Garvie, a general practitioner in good old Halifax, England: 

“But why the first case in the household was, on the average, more serious than the sporadic, and why the ‘clumping’ should occur, is difficult to understand. Casual observation might lead one to suppose that the spread was due to actual contagion from one house to another. At first I regarded it simply as due to ‘neighbourliness,’ but later on became convinced that this could only be a partial explanation of the spread. In many of the households affected in a ‘clump,’ a suggestion of being in any of the other affected houses was absolutely denied. It will further be noticed that within one particular ‘clump’ two or three houses commenced on the same date, and further, owing to the general fear of the epidemic, spread by newspaper reports and other methods, if the epidemic was known to be present in a house, the house was usually shunned by neighbours. In many cases the houses were not in direct contact but separated by the breadth of the street or by garden walls ... but why people within small radii of one another, of all ages, of different occupations, not coming in actual contact with one another, should develop synchronous attacks, still remains a mystery to me.”

Quite a history of events:  Garvey's conclusion makes for sobering reading and excellent advice:

“I am fully aware how little importance will be attached to the views expressed by those who frame regulations, but with the experience gained in over 100 cases and with many hours spent in analysing the observations made, I cannot help but express the view that if public health authorities canny be a help to the general practitioner, they should at least refrain from being a hindrance.”

In the era of modern computing, such detailed fieldwork is dispensed with, and instead, models and retrospective database analysis are the mainstay for investigation. There is no use asking overnight experts and media pundits for advice; the matter of transmission is a lot more complicated than it appears. 

References

Tyrrell, D. A. J. (David Arthur John). Common Colds and Related Diseases. London: Arnold, 1965. Print.

Tyrrell, D. A.J. “COMMON COLDS AND RELATED DISEASES.” British medical bulletin 23.2 (1967): 124–128. Web.

Andrewes, C. H. (Christopher Howard). The Common Cold. London: Weidenfeld and Nicolson, 1965. Print.

Allen TR, Bradburne AF, Stott EJ, Goodwin CS, Tyrrell DA. An outbreak of common colds at an Antarctic base after seventeen weeks of complete isolation. J Hyg (Lond). 1973 Dec;71(4):657-67. doi: 10.1017/s0022172400022920. PMID: 4520509; PMCID: PMC2130424.

Paul, J.H. & Freese, H. L. (1933). An epidemiological and bacteriological study of the 'common cold' in an isolated Arctic community (Spitzbergen). American Journal of Hygiene 17, 517.

Garvie A. The spread of influenza in an industrial area. BMJ1919;2:519-23.