4104 Rosemary Street
Chevy Chase, Maryland 20015
April 16, 1970

Dr. Joshua Lederberg

Professor of Genetics

Stanford University Medical Center
Stanford, California 94305

Dear Dr. Lederberg:

I have your letter of April 14th with its suggestion that I undertake
the preparation of a textbook on yellow fever. This is not possible at the
present time because of previous commitments.

The preparation of a letter to the editor is, I believe, inadvisable
from my standpoint since I have been so intimately connected with pushing
the eradication program in the past. I still hold an appointment as* (below)

I have decided to send you the draft of a letter dated April 6 addressed
to you which was superseded by the one you received under date of April 8.
It is my thought that this letter gives you something more of the background
while being somewhat repetitious.

The real purpose of this letter, however, is to advise you that a
volume has just come off the press which devotes a considerable amount of
space to the eradication concept and to the eradication of two African mos-
quitoes, Aedes aegypti and Anopheles gambiae. This volume has the title
Building the Health Bridge: Selections From the Works of Fred L. Soper,
published by the Indiana University Press, Bloomington, Indiana.

You will find in it sufficient information, I believe, to convince
you that your ecological friends are mistaken in insisting that "no inver-
tebrate pest had ever been intentionally eradicated over a significantly
large area." I would point out that the area involved in the eradication
of aegypti has covered many thousands of square miles, inhabited by many
millions of people, and has been going on for ever three decades, actually
ever since 1933,

To be specific in answering the questions in your last paragraph, I
would emphasize the fact that Aedes aegypti was literally eradicated in
Mexico and in Brazil. The eradication o aegypti in the Federal District
and in six states of Brazil, and in large parts of other states, was accom-
plished during the period 1933-1940 when I was in charge of the program and
had every opportunity to check and double check the results. The real test
of eradication, of course, is the interruption of all control measures thus
giving the insect an opportunity to return in force if still present.
Brazil was entirely free of Aedes aegypti for about ten years. Belém, at
the mouth of the Amazon, was found reinfected in 1967, and the extent of
the reinfestation suggested that it had been present in that area possibly
a year or longer before being identified. Resurveys in other parts of
Brazil show them to be still free of this mosquito.

*Special Consultant to the Office of International Health of the Public
Health Service.
Dr. Joshua Lederberg 2 April 16, 1970

Your question regarding the prospect of getting aegypti eradicated in
the Caribbean is, of course, one of opinion. Some parts of this area suf-
fered heavily from dengue outbreaks in 1963 and 1964 and again in 1969. The
increasing importance to this area of the tourist trade has caused a number
of the Governmental units in this area to renew their interest in aegypti
eradication. The two serious holdouts in this region are Venezuela and the
United States. Venezuela has had extensive epidemics of dengue twice in the
past ten years. The appearance of hemorrhagic dengue, such as has been seen
in Asia and the Western Pacifie in recent years, would undoubtedly stimulate
aegypti eradication fast.

A point which has not been properly publicized is the 1969 reinfesta-
tion of the city of Colén in Panam&. In 1949 jungle yellow fever was dis-
covered at a place called Pacora, not far from the Canal Zone. Later in the
same year yellow fever cases did occur in the Zone itself. At the beginning
of the United States occupation of the Canal Zone, the treaty with Panama
gave to the United States the responsibility of the sanitary service in the
cities at the two ends of the Canal, Panam& City on the Pacific and Colén on
the Caribbean entrance. Thus it was that Gorgas was able to bring about the
elimination of yellow fever from Panama between 1904 and 1906.

In recent years the United States has no longer intervened directly
in the sanitation of these two cities. In 1949 when yellow fever virus did
appear in this area, the United States authorities collaborated most actively
with the Panamanian Government in vaccinating the exposed population and, I
believe, did help in the solution of the Aedes aegypti problem. The Congress
of the United States appropriated some $600,000 for this crisis.

That the 1949 invasion of the area by yellow fever virus was not unique,
continuing studies by the Gorgas Memorial Institute revealed another invasion
by the jungle virus in 1956. ‘Thus it is that the reinfestation of Colon with
Aedes aegypti is a definite threat to the reinfestation of not only the Canal
Zone but also of Panama City and of many other towns of the country.

A point on which the United States is wide open for criticism is the
statement which has been made repeatedly that the United States has not had
outbreaks of dengue during the 1963-1964 and the 1969 outbreaks in the Carib-
bean. This statement overlooks entirely the outbreaks in Puerto Rico on both
occasions. There were some 30,000 cases reported in 1963, while surveys of a
limited area carried out by the U.S. Public Health Service indicated that
probably only 10% to 15% of the cases which occurred had been reported. The
question remains, Can the United States authorities say there has been no
dengue in the United States when tens of thousands of cases have occurred
in Puerto Rico?

You mention the possibility of using material from my letters. In
answer I can say that I am anxious to have material used if it can be of valve.
I would suggest, however, that drafts be sent to me for correction or modifi-
cation before publication.