4104 Rosemary Street
Chevy Chase, Maryland 20015
April 8, 1970

Dr. Joshua Lederberg
Department of Genetics
School of Medicine
Stanford University
Stanford, California 94305

Dear Dr. Lederberg:

I have at hand the xeroxed copies of two of your columns referring to
yellow fever and also to the Lassa virus fever. In attempting to comment on
the one entitled "Yellow Fever Still Survives in Jungles of Africa, Brazil,"
I found myself practically writing a textbook on yellow fever. I am instead
going to point out a few items in which your article is misleading, but
shall not go into the yellow fever situation in depth.

The statement that "vaccination and quarantine of exposed travelers
have kept the virus out of this country" is not backed up by the facts.
An efficient yellow fever vaccine was not available until 1937 or 1938, and
for many years now there has been no presentation of suspect cases at qua-
rantine to be excluded. The only breach made in quarantine since the early
part of the century was the case you cite in 1924,

You refer to Walter Reed and his fellow volunteers in Cuba. As a
matter of historical fact, Walter Reed was not a volunteer and did not
participate as one of the experimental subjects in any part of the yellow
fever investigations in 1900-1901.

You lump Africa and Brazil together as maintaining yellow fever only
because it continues as a harmless disease among monkeys in the two conti-
nents. Yellow fever does not kill the monkeys of Africa but is quite fatal
to some species of monkeys in the Americas. On the other hand, yellow fever
as a human disease does continue in Africa, whereas the campaign of the Rocke-
feller Foundation for the eradication of yellow fever in the Americas between
1918 and 1934 did, with the cooperation of the infected countries, result in
eliminating the continuing endemic human yellow fever transmitted from man to
man by the aegypti mosquito. Since 1934 the few small outbreaks of urban yel-
low fever have served a useful purpose in keeping pressure on the program for
the eradication of the aegypti mosquito. They have emphasized the permanent
threat of yellow fever to the urban populations with continued infestation of

Aedes aegypti.

The statement that the Latin American health authorities mounted an
aggressive campaign in 1940 is misleading. The aggressive campaign was based
on action taken, first, at the Pan American Sanitary Conference in 1942 and,
second, at the Directing Council meeting of the Pan American Health Organiza-
tion in 1947, The eradication resolutions were introduced in the first instance
by the delegate of Bolivia and in the second instance by the delegate of Brazil.
I know that on both occasions the American delegate, Dr. Thomas Parran, was
consulted beforehand by the delegates of Bolivia and Brazil. In each instance
assurance was given that the United States would support the resolution. Thus
the obligation for eradication in the Americas was assumed equally by the
United States and by the other representatives of the Western Hemisphere.
Dr. Joshua Lederberg 2 April 8, 1970

In 1958 the Pan American Health Organization certified the eradication
of aegypti in many of the countries of South America and Central America.
Annually since that time the countries of the Americas have yoariy voted sup-
port for the program of eradication and have urged the delinquent countries
to keep their commitments.

In 1961 Mexico forcibly called the attention of the Directing Council
of the Pan American Health Organization to the failure of the United States
to participate in the eradication program. In 1962 the Mexican Government
put the eradication of Aedes aegypti on the agenda for the meeting of the
Presidents of Mexico and of the United States in that year. As a result of
this pressure, after high level discussions within the administration with
representatives of the State Department, of Health, Education, and Welfare,
and of the Bureau of the Budget, in 1962 the Surgeon General of the Public
Health Service was authorized to commit the United States to the eradication
of aegypti in our southern states, in Puerto Rico, and in the Virgin Islands.
The Congress of the United States did in 1963 appropriate $3,000,000 for the
year's effort. This money became available in October 1963. In 1969, after
an expenditure of some $56,000,000, the program was abandoned completely with
nothing to show for the effort.

I am particularly concerned with the statement that the "aim of total
eradication of the mosquito was undoubtedly too ambitious." In dealing with
the Aedes aegypti mosquito, one cannot afford not to eradicate. The continu-
ing cost of eet control efforts within a short time cost much more than a
proper eradication effort. In this matter I can speak as one having had con-
siderable experience with this mosquito.

At long last I am coming to a point on which we thoroughly agree,
namely, "it relied too heavily on rote uses of pesticides like DDT." The
routine application of pesticides can be quite effective in the gross reduc-
tion of a given insect population. But the careful searching out and destruc-
tion of individual containers breeding aegypti is essential in an eradication
effort: 90% efficiency--even 99% efficiency--is gross failure in an eradica-
tion effort.

Your disagreement with the Senator who indicated that not a single
case of yellow fever has been reported in the last forty years is, of course,
quite proper. Your citation of the Senegal outbreak of 1965 might have been
further supported by an even more extensive outbreak of yellow fever in the
fall of 1969 in several countries: Upper Volta, Ghana, Dahomey, Nigeria, Togo,
Niger, and possibly others in the area just south of the Sahara.

I realize fully that I am, with regard to yellow fever, not in a posi-
tion to set the standards for newspaper columns on the subject. I am, however,
very much interested in keeping the yellow fever and dengue situation before
the public, because of the things I have seen yellow fever do since I first
went to South America in 1920.

It may interest you to know that many of the Latin American workers
cannot understand how the United States could have spent so much money without

appreciable results. The demonstration of the eradicability of Aedes aegypti
was made in Brazil in 1932-1933. All of the countries of South America
Dr. Joshua Lederberg 3 April 8, 1970

excepting Venezuela, the Netherlands Guiana, and a small area of Colombia
were successful in eradicating Aedes aegypti, as were also Panama, the five
Central American republics, and Mexico. i Mexicans cannot understand why,
if they were able to eradicate aegypti on their side of the frontier between
their country and ours, it is impossible to eradicate it on this side of the
border. Up to October 1969, Mexico had been reinfested nine times. Main-
taining a vigilant service and cleaning up each reinfestation as it comes
represent : continual expenditure which would be unnecessary were the United
States to clean up aegypti on this side of the line.

The United States, at the 1969 meeting of the Directing Council of the
Pan American Health Organization, proposed an in-depth cost benefit analysis
of the prevention of Aedes aegypti-tranamitted diseases, yellow fever, dengue,
and the hemorrhagic fever of ae It has been intimated that the United
States would voluntarily contribute to the expense of such a study. There
was a recent meeting of the preliminary working party assigned to establish
the parameter for such a study. The report of this working group has not yet
been released, but I understand that considerable weight is being given to
the need for the prevention of dengue, which caused heavy outbreaks in the
Caribbean and northern parts of South America in 1963 and 1964 and again in
1969, without, however, there being any observed hemorrhagic cases such as
have been associated with outbreaks of dengue in the Western Pacific and
Asia since 1956.

Several islands and countries of the Caribbean are showing renewed
interest in eradicating aegypti because of the impact of dengue on their
tourist trade.

Of one thing we can be sure, ahd that is that we have not heard the
last of Aedes aegypti, yellow fever, and dengue. I would point out that
only a very matt percentage of the cases of jungle yellow fever which occur
are ever reported. Yellow fever is unique among the epidemic diseases, in
that practically no cases are listed unless either pathological or serological
confirmation of the case is at hand. As you must know, the jungle type of
yellow fever occurs often at great distances from centers of population, so
that a very small percentage of the actual cases ever get reported. Even so,
since the commitment to eradication on the resolution of Brazil in 1947,
yellow fever has occurred on the island of Trinidad and in all of the coun-
tries of the mainland of the Americas excepting Canada and the United States
in North America, El Salvador in Central America, and Chile and Uruguay in
South America.

In closing, I would point out that I have retired some years ago from
the Pan American Health Organization and can be reached best at my home
address.

Sincerely yours,

f .
fin foue-

f

SER
Fred L. Soper