The winter of 1940-41 saw one of the worst measles epidemics in the history of the United States. It was particularly severe along the Atlantic seaboard, in large urban areas. In some school classrooms in Philadelphia, for example, the rates were as high as 60 or 70 percent during the whole period of the epidemic, though this does not mean that any such proportion of children was affected simultaneously.

But in three schools in or near Philadelphia, something extraordinary took place. The number of cases of measles that could reasonably be traced to contacts in the schoolroom was very much smaller. If we exclude children who were immune because of previous infections, and those who caught the disease from brothers and sisters while staying at home in quarantine, the rates were only 12 or 14 percent.

This apparent miracle was in reality the culmination of years of tedious work by various groups of scientists—engineers, doctors, research workers in commercial laboratories, all experimenting with a wonderful new means of cutting down air-borne infection. It came as the successful conclusion of an investigation by the Medical School of the University of Pennsylvania. The classrooms were chosen to test the theory, developed through years of study by W.F. Wells and his wife, M.W. Wells, that contagious epidemics are spread because people congregate in the confined air of closed rooms during cold weather. The scientists were confident that they could control the spread of epidemics of childhood contagions in schools, though even they were surprised at their success in reversing the order of nature by checking a measles epidemic among young children while it was rampant in the older classes that are normally more immune.

The story is a simple one. The children who were so effectively protected spent their days in classrooms in which a special type of ultra-violet lamp had been installed above the eye level and facing upward. Its rays are roughly similar to those in a sunlamp, although concentrated in the area of rather shorter wave length. As the air in a room with such a lamp circulates between irradiated and unirradiated zones, viruses, bacteria or other minute life that it contains are inactivated or killed at varying distances, the time required being lessened with the nearness to the source of the rays.

This sounds simple, yet it may prove one of the most remarkable advances in recent medical history. Measles is only one of numerous diseases that may be effectively checked in this way. Among the others are whooping cough, mumps, chicken pox and pneumonia. Laboratory experiments on animals have shown that the tubercle bacillus is vulnerable to ultra-violet radiation. Infantile paralysis remains a problem, since it does not come, like many other infections, with the closing of doors and windows in cold weather.

Among the diseases that may be checkmated—and this will probably be of most interest to a majority of my readers—are influenza and the common cold. In fact, for a fairly small sum anybody can now greatly reduce the likelihood of catching cold, provided he will install these lamps in the rooms where he spends the greater part of his time, and will be careful about exposing himself in crowded public buildings at periods of the year when colds and influenza are prevalent. As time passes, it is reasonable to suppose that increasing numbers of these public buildings will themselves be equipped with such lamps and the danger of infection thereby correspondingly reduced. When that day comes, unbelievable as it now seems, colds, influenza, pneumonia and the childhood diseases already listed ought to be very largely a thing of the past, so far as accidental infection is concerned.

If you have one of these lamps in your office, you need worry less about getting a cold from a visitor, provided you and he remain in the room with the lamp, and provided that it is kept continuously on. While 100-percent success cannot be guaranteed, the chances are strong that you will not take his cold. (The cautious and conservative medical profession would not make such a firm and optimistic statement as that, but I believe the evidence substantiates it.)

In the schools of Philadelphia, as already mentioned, the younger children were protected with germicidal lamps, and the older ones of high-school age were not. The younger children (excluding the groups described earlier as immune, or as infected at home) had only 25 percent as many cases of measles as the older ones. But measles is a disease of early childhood. Under normal conditions the younger children should have had many more cases than the older ones. If controls could have been better, if lamps could have been installed not only in the classrooms but in the school hallways and in the homes, in buses and street cars, theatres, etc., the record might have been better still.

Germicidal lamps are not only effective in controlling the epidemic spread of contagion, but can be used to prevent respiratory infections from traveling through a confined group. This is shown by the experience in a large orphanage near Chicago, where some of the children are now protected by lamps and others are not. On one unprecedented occasion twelve nurses came down with colds simultaneously—far too many to permit them all to stay at home until they were well. As a result, in a room without the lamps where there were a large number of babies, all but one caught cold. Yet when the same nurses, in spite of their colds, took care of the babies who were protected by the light, not a single infection resulted. In two years, in rooms without lamps, there were sixty-four “cross infections,” or contagions, with respiratory diseases—infections, that is, that could be traced to other children, nurses, doctors, or visitors. Over a period of many months, there has been just one infection with a respiratory disease among children guarded by light.

Results similar to those just described have been found in a children’s hospital in a large Eastern city; here also, part of the children were protected with germicidal lamps and parts were not. In the former group, out of 150 children, during six months beginning with December, there were only 4 patients with infections, 3 of which were of the respiratory type. Among 224 children not protected, there were 28 infections, one-half of which were respiratory. But in fact, the difference is even more favorable than it seems. Two of the three respiratory infections in the first group occurred late in May, and it was afterward discovered that the lamps had been burned steadily for such a long time that the bulbs had lost some of their germicidal power.


Today, advanced physicians are coming to recognize the reality of air-borne infection, but the control of the epidemic spread of contagion is a new factor in public health. A hundred years ago, people complained constantly of ailments of the intestinal tract. Slowly and laboriously, yet on the whole effectively, we have learned to purify our drinking water, to pasteurize our milk and to see that our foods are not infected. Engineers have drained our marshes, screened our houses and otherwise kept out of insect bearers of disease. Today we are about to cross the last great frontier of sanitary control and purify the air.

The work done at the University of Pennsylvania has shown that there are a number of diseases whose causative agents are normally invisible and can remain suspended in the air indefinitely. It was once thought that you would not get a cold if you kept at double arm’s length away from an infected person, but we have found that this is nonsense. Infection is possible if you are in the same room where such a person is or has been recently, or even in one of a series of rooms, provided that the air circulates readily through them.

The research workers have proved this by a group of ingenious laboratory experiments. A laboratory animal infected with one of the air-borne diseases that have been mentioned is placed in a small cage in a large room. A healthy animal of the same species is placed in another small cage in the same room but a number of feet away. In an overwhelming majority of cases the second animal receives the infection. The same result is found when a healthy animal in a cage is subjected to air into which some of the infective agents of various diseases have been artificially introduced.

An important use for these germicidal lamps is in hospital operating rooms. There they have produced a sharp reduction in post-operative infections. Their importance in hospitals in general, and especially in open wards, is obvious. Cross infection, between patient and patient, or among patient, nurse, physician and visitor, is a serious problem for hospitals.

I should mention that it is possible to sterilize air, and prevent infection, by other than germicidal lamps. It has been discovered for instance that a room can be filled with a fine mist of propylene glycol, which kills much of the organic life in the air. The concentration is so small that there is no obnoxious odor, and clothing and other delicate surfaces are not stained or injured.

Germicidal lamps are sometimes introduced into an air-conditioning system. The air in the room is made to pass through an irradiation chamber so that when it returns, most of the organisms have been eliminated. In fact, however, it is simpler and more effective merely to turn on the germicidal lamps in the room itself. The natural circulation of the air is as effective as though the entire amount went through an irradiation chamber one hundred times an hour. (The only reason for pointing the lamps upward in indirect-lighting fixtures above the eye level is to avoid burning the eyes of people who look directly at the lamp—a painful experience, but not usually serious. It would of course be more efficient to irradiate every part of the room than merely the upper half.)

Even if the lamp is placed above the eye level of a person standing in the room, and has its rays directed upward, it will have killed a large part of the germs in that room within a few minutes, though for cautionary reasons it is well to keep the lamp lighted very much longer. (I am speaking of an ordinary-size room, say roughly twelve by sixteen by eight.) Of course, if germs are being added continually by the occupants of the room, the light should also be on continually. The cost of operation is insignificant with electric current at an average price.

Germicidal lamps are not especially expensive; they range from perhaps $10 to $30 or $40 each, not including the cost of installation, and are now being made by at least four manufacturers. It should be strongly emphasized that they must be installed by an expert. Your local electrician is not at present competent to arrange such an installation. Neither is your local physician, unless he has especially qualified himself by study in the last few months, and such study has been undertaken by very few.

Until very recently, prevailing medical theory was against the idea that infections could be carried by air. It had long been recognized that diseases were transmitted through water, milk, mosquitoes and vermin, and through common use of utensils, towels, etc. The notion, however, that the air itself could be a source of contamination was rejected as belong to the “miasmic-vapor” era of a hundred years ago. Even today, a nurse is not permitted to excuse herself, if a cross infection occurs among her patients, on the ground that air-borne germs have been responsible, and not her own careless handling of dishes, towels, implements, etc. Lately, however, motion pictures have been made, using special new techniques, under which some of these air-borne infections, hitherto invisible to the naked eye, have actually been seen. The Journal of the American Medical Association and other reputable medical periodicals now fully accept the idea of air-borne infection, and have shown keen interest in the use of germicidal lamps and other techniques to combat it.

It is difficult at present to conduct experiments on human beings in the use of the germicidal lamps because most people pass through many environments in the course of a day, and it is impractical to have lamps in all of them. A person might be shielded by lamps twenty-three hours and fifty-five minutes a day, and then spend five minutes in an unprotected elevator, bus or street car, and there pick up an infection. In the case of colds and some other diseases, there are several types of germs and viruses, and you can be infected with more than one simultaneously. Even with organisms of the same type, it is possible to have a multiple infection.

Very recent experiments in the dormitories of an Eastern school seem to point to an interesting conclusion. If students are protected all night while asleep and then spend the day in crowded, unprotected classrooms, the number of colds they acquire appears to be less than would normally be expected in these circumstances. It is possible that breathing germ-free air all night is sufficiently beneficial so that in the daytime numerous infections remain below the level of the individual’s power to throw them off. These experiments, however, have not been continuing long enough to justify any firm conclusion whatever.

The ideal group for a thorough tests of lamps would be soldiers in barracks. These men spend most of their time in the open air, and any given individual enters only a few buildings each day. It would be entirely possible to test the lamps in an army camp.

Such a test might also prove to have the highest practical value. During the last war, American soldiers both here and in France were the prey of one epidemic of respiratory diseases after another. The time lost was very serious, even worse than that in the civilian population, where 400,000,000 colds a year continue to cost us $500,000,000. If the recent experiments with the lamps are confirmed by experience in the army—and there is every reason to hope that they will be—here is a measure of national defense of the very highest importance. But whether the army immediately uses the lamps or not, we can look forward confidently to the fact that within another few years at most, control of air-borne infection will be on its way to join control of infections through water, milk and solid foods. Another great frontier will have surrendered to man’s onward match.