CHAPTER III. The Discoveries of the Reed Board

THE DISCOVERIES OF THE REED BOARD

Dr. Reed wished to make his demonstrations as convincing and spectacular as possible. It was an entirely new idea, and his conclusions excited a great deal of adverse comment and criticism. This theory was so contrary to what most men thought had been their practical experience that it was received with scant consideration.

He had a small frame house built, fourteen by twenty feet, well screened-in with wire netting, so that mosquitoes could not get in or out. This building he had divided into two compartments by a partition extending down the center, made of wire netting, and it was known as the infected mosquito building. It was well ventilated. Most persons at this time believed that in some way the air conveyed yellow fever. Dr. Reed wished to show that this was not the case.

He put two non-immunes in this building, one in each room. These two men breathed exactly the same air, and had exactly the same surroundings, with one single exception which I will in a moment point out. But they were entirely separated by the wire netting. He let them live and sleep in these rooms for several days, so as to demonstrate that there was no yellow-fever infection in the building. He then put fifteen infected stegomyia in one of the rooms; left the man in this room for thirty minutes, announcing that the room was now infected. He took the man out of this infected room, but left in the other room two men on the other side of the wire netting. He stated that the man who had stayed thirty minutes in the infected room would come down with yellow fever within three or four days, and that the other men, who were only separated from him by wire netting, and who breathed and were surrounded by exactly the same air, would not get sick.

He explained that the only difference between the two rooms was that in the infected room, infection had been brought about by liberating there fifteen stegomyia mosquitoes which had previously bitten patients sick of yellow fever. The man from the infected room was on the afternoon of the same day again placed in this room for twenty minutes, and on the following day he was a third time put in the room for fifteen minutes. On the first visit he was bitten by seven mosquitoes; on the second, by five; on the third, by three. At the end of the fourth (Christmas) day, Reed showed the man from the infected room down with yellow fever, and the men who had lived and slept in the other room, separated only by wire netting, perfectly well. He called attention to the fact that the only difference in the exposure of these men was that the sick man had been in a room for thirty minutes, with fifteen infected stegomyia mosquitoes. He claimed that this was a demonstration that the female stegomyia mosquito could transmit yellow fever, and that the atmosphere alone could not. Many of the visitors to Dr. Reed’s camp were clinically familiar with this disease, and the case was sufficiently marked to be easily recognized by all as being a case of yellow fever.

Dr. Reed then announced that he would disinfect the room so that it would no longer give yellow fever. When it was prepared, he again placed a non-immune in each room, left them there for several days, and they remained perfectly well. He explained that he disinfected the room by simply catching all the stegomyia mosquitoes which he had formerly liberated in the room.

This demonstration made a very profound impression. Many, however, still urged that while it was evident that the female stegomyia mosquito could convey yellow fever, it was equally evident from the history of epidemics of this disease that it could be and was generally conveyed in other ways, such as soiled clothing, bedding, the bodies of yellow-fever dead, persons sick of the disease, etc.

Dr. Reed had a small house built, made almost air-tight and with scarcely any ventilation. This building was known as the infected-clothing building, and was purposely so constructed as to exclude anything like efficient ventilation. It was placed on the opposite side of a small valley, about eighty yards from the infected mosquito building, and they were both about seventy-five yards distant from the camp proper. Both houses were provided with wire screen windows and double screen doors, so that mosquitoes could be kept without or within the building, as the experimenter might desire.

In this building he placed material obtained from Las Animas, the yellow-fever hospital of the Health Department of Havana; mattresses on which yellow-fever patients had died, soiled by their excreta and discharges; sheets, pillows and pillow-cases stained with black vomit; the pajamas which patients had worn at the time of their death. It was Dr. Reed’s desire to have this material infected if it were possible to become infected in this way. Dr. John W. Ross, the superintendent of Las Animas Hospital, therefore gave the matter his personal attention, saw to the packing of this material in chests for transportation to Camp Lazear, and before the chests were closed, had basins of black vomit and other excreta from yellow-fever patients poured over the contents of the chest. If there were any possibility of such material becoming infected, infection certainly would have followed such procedure.

Dr. Reed had this material opened up and spread out in the close room I have described. He called for volunteers to sleep in this room. Dr. R. P. Cook of the Army, and several soldiers quickly responded. These men put on the pajamas soiled as described, and slept on the mattresses and bed clothing soiled beyond description. For a period of twenty days they spent the nights in this building, but for the sake of general health were allowed to go out during the day. All the men remained perfectly well, and no case of yellow fever was developed from such exposure.

This set of experiments was generally accepted as proving that yellow fever was conveyed from man to man by the mosquito alone, and that it was not transmitted in any other way. A great many persons, however, were still skeptical. The experimental camp had been named “Lazear” in memory of Dr. Lazear, a member of the Board, who had died a few months before of yellow fever, contracted while prosecuting this work.

The Board then took the blood of a yellow-fever patient in the first three days of his sickness, and injected it with a hypodermic syringe into a non-immune. He promptly developed yellow fever. This proved that the blood of a patient suffering from this disease could transmit yellow fever without passing through the body of the mosquito. From this experiment of injecting the blood directly from one person into another it was argued that it might not be a yellow-fever parasite that was injected, but a toxin.

The Board then took the blood within the first three days of sickness from this second patient who had been given his disease from the blood of the first patient, and injected it into a third patient. This third patient developed the disease at the proper time. This experiment demonstrated that the virus so conveyed was capable of multiplying; that it was a living germ and not merely a toxin or chemical body which transmitted the disease.

The Board then took the blood of a patient collected in the first three days of his sickness, and passed it through a Pasteur filter so fine that it would stop any particle large enough to be seen with a microscope of the highest power. This blood when injected into a non-immune still gave yellow fever. This demonstrated that the parasite was sub-microscopic; that is, too small to be seen by a microscope of even the highest power.

They then took the blood of a yellow-fever patient within the first three days of his disease, heated it to 55° C., and injected it into a non-immune. The non-immune did not develop yellow fever. This was repeated three times. This experiment proved that the living parasite in the blood of the yellow-fever patient was killed by being raised to a temperature of 55° C.

The conclusions announced by the Board were as follows:

That yellow fever is conveyed from man to man only by the bite of the female stegomyia mosquito, and that this mosquito, to become infected, must suck the blood of the yellow-fever patient within the first three days of his disease.

That after biting the patient, twelve to twenty days must elapse before she herself is able to convey the infection. This period is known as the period of extrinsic incubation. Extrinsic incubation in Havana was found to be considerably longer during the cool months of winter than during the warm period of summer.

That after the non-immune human being had been bitten by the infected stegomyia mosquito, an incubation period of from three to six days elapsed before the man began to show symptoms of yellow fever. The shortest period of incubation in Dr. Reed’s cases was two hours less than three days, and the longest period, two hours more than six days.

That the blood, taken at the proper time and injected into a non-immune, would also cause yellow fever; that the disease was caused by a parasite, and that the parasite was sub-microscopic.

These discoveries have been of enormous benefit to mankind, and upon them has been based the sanitary work against yellow fever which has been so successful. At first blush, however, it was not evident to what extent it would be of practical use to us.