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hospitals the following day. The organisms isolated from
Miss B and her landlady were both shown to belong to
S. typhi Vi phage type A.
Epidemiology
It emerged that the two women lived together, sharing the
same kitchen and toilet. Neither had been abroad. They
seldom ate out except on holiday, and had relatively few
visitors. But one of these was a middle-aged Swede, Mr. J,
who lived nearby. From time to time he had done small
services in the house and garden for Mrs. K and had
occasionally used the washing and toilet facilities. He said
that in 1954 he had spent a holiday in England and had
developed typhoid fever within a few days of returning to
Sweden. Enquiries at the hospital in Sweden where he had
been treated confirmed his statement, and also revealed
that he had been infected with type A of S. typhi. However,
he was reported not to have been excreting this organism
when discharged.
Although many stool specimens from this man were
examined over a 3-month period, following the discovery of
his association with the two cases of typhoid (Miss B and
Mrs. K) in 1969, none yielded S. typhi. Requests for blood
for antibody tests were made, but all were refused. All
other enquiries were unproductive and although there was
no direct proof, this man was suspected of being the source
of infection of the two women.
In August 1971, Miss M, a 43-year-old receptionist, was
admitted to a South London hospital with an un-diagnosed
illness of several weeks' duration. She eventually developed
a breast abscess from which S. typhi was isolated. This
strain was sent for phage typing, but was reported as an
untypable \/i strain. Miss M lived in lodgings and in
accordance with routine investigation faecal specimens were
obtained from her landlady, Mrs. V. These specimens
yielded type A of S. typhi.
The importance of this unexpected finding became
apparent when it was discovered that Mrs. V lived in the
same block of flats as, and was the sister of, Mr. J, who
had been associated with the typhoid illness of the two
elderly women in 1969. Mr. J, stayed with his sister
during his visit from Sweden in 1954, after which he had
contracted typhoid. It was also discovered that Mrs. V had
occasionally exchanged visits with Miss B and Mrs. K.
As Mrs. V remained symptomless, and had no serological
evidence to suggest a concurrent or recently typhoid
infection, it was concluded that she was a chronic
carrier. As she had a history of enteric fever as a child
it was possible that she had been excreting S. typhi
since then.
Her association with four cases of enteric fever was
now quite evident (Fig. 1). The fact that one of these was
infected with S. typhi of a different phage type from the
other three was at first puzzling.
Discussion
The presumption of a casual relationship between a typhoid
carrier and cases of enteric infection rests on an assessment
of several epidemiological features. Vi phage typing of
S. typhi (Craigie and Yen, 1938) has added precision to
this assessment (Anderson and Williams, 1956).
16
In all four cases described here, there were opportunities
for infection by the suspect carrier, and in three the strain
belonged to type A, the same type as that of the carrier.
Although this is one of the commonest Vi types of S. typhi
(Anderson and Williams, 1956), typhoid carriers (and
therefore the opportunities for infection) are so rare in this
country (Anderson, 1971), that when three otherwise
unexplained cases of typhoid fever are found to have an
association with a carrier of S. typhi of the same type with
which they were infected, it seems reasonable that this
carrier should be suspected of being the source of infection.
The relationship between the carrier Mrs. V, and the
fourth case of typhoid fever, Miss M, is more intriguing.
In this instance the opportunities for infection were
obviously considerable. But the strain of typhoid bacillus
isolated from this case was untypable, while the strain
isolated from Mrs.V was type A. By conventional concepts
such a finding suggests a different source of infection
(Anderson and Williams, 1956). Nevertheless, in apite of
the discrepancy in phage types, the occurrence of a case of
typhoid in the home of a known carrier was evidence too
impressive to discount. Also, excretion of two phage types
of S. typhi by a single carrier, while extremely uncommon,
has been reported (Craigie and Felix, 1947; Henderson and
Ferguson, 1949; Anderson, 1951). So there were good
grounds for believing that Miss M had been infected by her
landlady Mrs. \/, in spite of the apparent difference in the
types of S. typhi initially found in the two women.
Confirmation of this was obtained when it was established
that the landlady was excreting both type A and an
untypable S/\ strain of S. typhi.
Why two phage types?
Whether the carrier had originally been infected with two
distinct phage types of S. typhi, or whether in vivo
transformation of a type A strain to an untypable strain or
vice versa, has occurred, has not been clarified. While
investigating the excretion of two phage types of the
typhoid bacillus by a long standing carrier, Anderson (1951)
showed experimentally that transformation of one type to
the other was caused by loss or gain of a phage.
Whatever the explanation for her carriage of two phage
types, it can be accepted that Mrs. V was the source of Miss
M's infection. This woman was therefore the probable
source of infection of four cases of typhoid fever covering
a span of 1 7 years and involving two different phage types.
We thank Dr. E. S. Anderson, FRS, Enteric Reference
Laboratory, Colindale, for the reports of the S. typhi phage
types and Dr. Gunnar Orn, Clinic for Infectious Diseases,
Linkoping, for the report on Mr. J.
References
Anderson, E. S. (1951). J. Hyg., Camb., 49, 458.
Anderson, E. S. (1971). Sunday Times, 31st December.
Anderson, E. S. and Williams, R. E. 0. (1956).
J. din. Path., 9, 94.
Craigie, J. and Felix, A. (1947). Lancet, 1, 823.
Craigie, J. and Yen, C. H. (1938). Canad. J. pubi. Hlth.,
29, 448, 484.
Henderson, N. D. and Ferguson, W. W. (1949),
Am. J. Hyg., 50, 349.