“During the year 1920 none of the keepers or their families, consisting of thirteen in number, were affected. The Halfway Rock Light Station where three keepers are employed did not contract this malady either in the years 1918 or 1920.
“For your information I might add that during the inspection trip in the months of January, February and March, 1920, all of the light stations in this district were visited, and it was found that they were all enjoying good health and had not been visited by the epidemic, with the possible exception of three stations which are located either on the mainland or close to where the keeper or his family were able to visit the nearby cities or towns.”
Although it has not been shown that completely isolated places have been visited by the disease, there is abundant evidence that such places have remained influenza free as long as the isolation has remained complete. Islands and lighthouses, which have not been in communication with the mainland, individuals living isolated on mountain tops, and ships at sea remained free from influenza even in the presence of a pandemic, as long as they did not come into communication with individuals sick with the disease. The following places remained free from influenza throughout the 1889 epidemic: the Isle of Man, several of the islands of the West Indies, particularly the Bahamas, Granada and St. Lucia, also the British Honduras, British Guiana, and the Seychelle Islands.
Even in 1918, when the paths of commerce reached nearly every portion of the world, we have examples of relative immunity of isolated places. Thus we know that the Esquimaux were attacked late in the course of the pandemic, and we have the statement of Barthélemy who traveled in 1919 to some of the oasis towns of the Sahara Desert, and there discovered that there had not only been no influenza up to that time, but also that they had not even heard of the pandemic.
Another type of isolated place is the closed institution. As early as 1709, Lancisi remarked that the prisons of the Inquisition in Rome remained free from influenza. Twenty-one prisons in Germany in 1889–90 remained entirely free from the disease. This was true of 39 prisons in England, some of which were in cities where the epidemic was most extensive. Linroth, who observed this same phenomenon in Sweden, makes the wise remark that, “the influenza conquers more easily the space of 500 to 1,000 kilometers than it does the small barrier made by a prison wall.” A convent in Charlottenburg housing one hundred women remained entirely free during the 1889–90 epidemic.
As a rule institutions of this sort have been unable to maintain a complete quarantine throughout the period of an epidemic, and the relative immunity has been demonstrated more in late invasions, at a time when the restrictions have become somewhat lax. Thus, in 1918, Winslow and Rogers, report that in an orphan asylum in New Haven, Connecticut, which had completely escaped during the month of October when the epidemic was at its height, one of the Sisters and the priest in charge came down with influenza about December 15th. By the 27th of December 127 cases had occurred in the institution within twenty-four hours, and by January 7th there had been 424 cases, with seven deaths out of a total population of 464. The probable source of the sudden outbreak of December 27th seems to have been the Sister first affected who, when convalescent, resumed her duties in the kitchen, which included the inspection and handling of the milk given out to the children.
Crowd gatherings.—Yet another phenomenon which would lead us to conclude that human intercourse is the most potent factor in the transmission of influenza is the fact that there is frequently a high increase in the influenza rate following crowd gatherings. Parkes observed long ago that persons in overcrowded habitations, particularly in some epidemics, suffered especially, and several instances are on record of a large school or a barracks being first attacked and the disease prevailing there for some days, before it became prevalent in the towns around.
In England, the weekly market played an important role in the spread of the disease in 1889. One frequently saw such reports as that: “The first case of influenza was a man who went to London daily.” Or, “All the earliest cases were men going to London daily, while their wives and families were later affected.”
In the epidemics at San Quentin Prison, it was noted that apices of incidence usually occurred on Tuesday and Wednesday. During the first epidemic it was these days of the second and third weeks. Stanley sees a direct connection between this fact and the fact that every Sunday morning large groups of the men were crowded together in a comparatively small auditorium where they saw moving pictures. On Sunday, October 20th, they sought to eliminate this source of spread by having a band concert in the open air, but the prisoners crowded around the band and were loud in their cheers, and on the following day there was a large increase in hospital admissions.
On November 24th after the second epidemic had apparently ceased the picture shows were again started after having been closed for over six weeks. The following Tuesday and Wednesday twenty-four well defined new cases were admitted to the hospital. On Thanksgiving Day there was a field meet between the various departments of the prison. About 200 prisoners took active part, while 1,600 prisoners were spectators. The meet was held in the open air, but the prisoners were closely packed and they cheered and yelled. For the three days following this celebration there were 9, 5 and 8 patients admitted respectively.