Measles WORLD OF MICROBIOLOGY AND IMMUNOLOGY368•
had begun to change infectious disease therapy. McCarty
treated children suffering from Pneumococcal pneumonia, and
he was able to save a child suffering from a Streptococcal
infection, then almost uniformly fatal, by the use of the newly
available sulfonamide antibacterials. Both of these groups of
bacteria, Streptococcusand the Pneumococcus, would play
important roles throughout the remainder of McCarty’s career.
McCarty spent his first full year of medical research at
New York University in 1940, in the laboratory of W. S.
Tillett. In 1941, McCarty was awarded a National Research
Council grant, and Tillett recommended him for a position
with Oswald Avery at the Rockefeller Institute, which was one
of the most important centers of biomedical research in the
United States. For many years, Avery had been working with
Colin Munro MacLeod on Pneumococci. In 1928, the British
microbiologist Frederick Griffith had discovered what he
called a “transforming principle” in Pneumococci. In a series
of experiments now considered a turning point in the history
of genetics, Griffith had established that living individuals of
one strain or variety of Pneumococci could be changed into
another, with different characteristics, by the application of
material taken from dead individuals of a second strain. When
McCarty joined Avery and MacLeod, the chemical nature of
this transforming material was not known, and this was what
their experiments were designed to discover.
In an effort to determine the chemical nature of
Griffith’s transforming principle, McCarty began as more of a
lab assistant than an equal partner. Avery and MacLeod had
decided that the material belonged to one of two classes of
organic compounds: it was either a protein or a nucleic acid.
They were predisposed to think it was a protein, or possibly
RNA, and their experimental work was based on efforts to
selectively disable the ability of this material to transform
strains of Pneumococci. Evidence that came to light during
1942 indicated that the material was not a protein but a nucleic
acid, and it began to seem increasingly possible that DNA was
the molecule for which they were searching. McCarty’s most
important contribution was the preparation of a deoxyribonu-
clease which disabled the transforming power of the material
and established that it was DNA. They achieved these results
by May of 1943, but Avery remained cautious, and their work
was not published until 1944.
In 1946, McCarty was named head of a laboratory at the
Rockefeller Institute which was dedicated to the study of the
Streptococci. A relative of Pneumococci, Streptococci is a
cause of rheumatic fever. McCarty’s research established the
important role played by the outer cellular covering of this
bacteria. Using some of the same techniques he had used in his
work on DNA, McCarty was able to isolate the cell wall of the
Streptococcus and analyze its structure.
McCarty became a member of the Rockefeller Institute
in 1950; he served as vice president of the institution from
1965 to 1978, and as physician in chief from 1965 to 1974. For
his work as co-discoverer of the nature of the transforming
principle, he won the Eli Lilly Award in Microbiology and
Immunologyin 1946 and was elected to the National Academy
of Sciences in 1963. He won the first Waterford Biomedical
Science Award of the Scripps Clinic and Research Foundationin 1977 and received honorary doctorates from Columbia
University in 1976 and the University of Florida in 1977.See also Microbial genetics; Microbiology, clinical;
Streptococci and streptococcal infectionsMMeaslesEASLES
Measles is an infectious disease caused by a virus of the
paramyxovirus group. It infects only man and the infection
results in life-long immunityto the disease. It is one of several
exanthematous (rash-producing) diseases of childhood, the
others being rubella (German measles), chicken pox, and the
now rare scarlet fever. The disease is particularly common in
both pre-school and young school children.
The measles virus mainly infects mucous membranes of
the respiratory tract and the skin. The symptoms include high
fever, headache, hacking cough, conjunctivitis, and a rash that
usually begins inside the mouth on the buccal mucosa as white
spots, (called Koplik’s spots) and progresses to a red rash that
spreads to face, neck, trunk and extremities. The incubation
period varies but is usually 10 to 12 days until symptoms
appear. Four to five days before the onset of the rash, the child
has fever or malaise and then may develop a sore throat and
cough. The duration of the rash is usually five days. The child
is infectious throughout the prodromal (early) period and for
up to four days after the first appearance of the rash. The virus
is highly contagious and is transmitted through respiratory
droplets or though direct contact. Measles is also sometimes
called rubeola or the nine-day measles.
Although certain complications can arise, in the vast
majority of cases, children make a full recovery from
measles. Acute local complications can occur if there is a sec-
ondary infection, for example pneumoniadue to bacteria
such as staphylococci, Streptococcus pyogene, pneumococci,
or caused by the virus itself. Also, ear infections and second-
ary bacterial otitis media can seriously aggravate the disease.
Central nervous system (CNS) complications include post-
measles encephalitis, which occurs about 10 days after the
illness with a significant mortality rate. Also, sub-acute scle-
rosing panencephalitis (SSPE), a rare fatal complication,
presents several years after the original measles infection.
Because hemorrhagic skin lesions, viraemia, and severe res-
piratory tract infection are particularly likely in malnourished
infants, measles is still frequently a life-threatening infection
in Africa and other underdeveloped regions of the world. The
microbiological diagnosis of measles is not normally required
because the symptoms are characteristic. However, if an acute
CNS complication is suspected, paired sera are usually sent
for the estimation of complement fixing antibodies to
measles. If SSPE is suspected, the measles antibodytitres in
the CSF (determining the level of antibodies present) are also
estimated.
Epidemiological studies have shown that there is a
good correlation between the size of a population and the
number of cases of measles. A population of at least 500,000
is required to provide sufficient susceptible individuals (i.e.womi_M 5/7/03 7:52 AM Page 368