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.