Droplet infection and spread through inanimate objects.—The actual mode of spread of the virus of influenza from one individual to another is unknown. The more generally accepted explanation is that the infecting agent leaves the body through the respiratory tract, usually in the spray of coughing or talking; contagion is by droplet infection, as is sometimes the case in other respiratory infections. Thorne and others have called attention to the capillary congestion of the conjunctivae very early in the disease. They suggest that possibly the mucous membrane of the eye is the site of infection.
There has recently been considerable discussion concerning the spread of influenza through inanimate objects.
Leichtenstern reviews the reports of 1889–93 in which influenza was supposed to have been transmitted through wares, merchandise and other inanimate objects. He concluded that the evidence in all of the cases cited was insufficient for conclusive proof. Such an example was the supposed importation of the disease in goods sent from Russia to the Grands Magazins du Louvre at Paris. In one day 100 people became ill and in a few more 500 were sick with influenza. The explanation was that the germs had been imported in goods sent from Russia to the store. Detailed investigation showed that this could not have been the case because no goods had been received from Russia for a period of three years. Another example is that of one of the two winter caretakers at the St. Gothard Hospice. One of the two men went down into the valley where he purchased supplies. Ten days after his return the man who had remained in the Hospice fell ill with influenza while his comrade remained well. It was stated that influenza was introduced into Basel by goods shipped to that place from the Magazins du Louvre in Paris. The first case occurred in a man who had been working at unpacking these goods.
Lynch and Cumming believe that droplet infection plays but a minor role in the spread of sputum-borne diseases, but that insanitary methods of washing dishes and eating utensils was the chief cause for the high rates of “sputum-borne” infections both in army and civilian life in 1918. They found that among 31,000 troops eating from tableware which was cleaned by kitchen police, the influenza rate was 51 per 1,000, while among 35,000 eating from mess kits which each individual washed himself the rate was 252 per 1,000. “Eighty-four per cent. of the cases occurred among those whose hands were contaminated by washing their own eating utensils.”
Among 17,236 employees of hotels, restaurants and department stores, who ate from machine washed dishes, there occurred 349 cases of influenza, while among 4,175 who ate from hand washed dishes there were 429 cases. The rate was but 20 per 1,000 in the former, while in the latter group it reached 103 per 1,000. Here again the chances of infection between the two groups were as one is to five.
These authors have records covering 252,186 individuals in scattered institutions in the United States. Among those eating from machine washed dishes the rate was 108 per 1,000 while those eating from hand washed dishes suffered at the rate of 324 per 1,000. The ratio was 1 to 3 between the two groups. Seventy-five per cent. of the cases occurred in that group which ate from dishes not disinfected with boiling water. They do not state the number of individuals in each of the two groups.
Lynch and Cumming claim that in the act of coughing only a few organisms are expelled from the mouth, rarely over 1,500, and conclude that transmission by direct contact through the air route but rarely, if ever, takes place. While about 1,500 organisms are expelled onto the floor by an act of coughing, a sterile glove wiped across the lips may pick up nearly 2,000,000 organisms. Such organisms may be readily transferred to inanimate objects which are handled by many people.
Hemolytic streptococci and pneumococci may be isolated with great regularity from the hands of carriers or patients, from table ware, inanimate objects touched by these patients, and from floor dust. Diphtheria and tubercle bacilli have been isolated from the hands and eating utensils of patients. The average count of a large number of restaurant dishwater specimens was 4,000,000 bacteria per c.c. The temperature of this water averaged 43° C. and the dishes were practically never scalded. The water was often so highly polluted, “that the dishes are more highly contaminated after they are washed than before washing begins. The spoon or fork is often freer from organisms just after being used by the restaurant patron than when taken from the restaurant’s polluted dish water.”
Major John S. Billings, epidemiologist at Camp Custer, reported that one of the larger organizations did not properly observe the regulation requiring that all mess kits and table equipment be properly sterilized. The disease appeared early and spread unusually rapidly in this particular organization.
In summarizing the subject of transmission through utensils, we may say that the evidence is suggestive but inconclusive. It is possible, even probable, that this is one mode of transmission. That it is the most important has not been proved. Lynch and Cumming do not take into consideration that the regiments with more sanitary methods of cleansing the dishes are apt to be those regiments with more sanitary habits throughout their daily routine. Those restaurants using mechanical dish washers are usually the cleaner restaurants.