116
A. SARAGEA ET AL.
VII. EPIDEMIOLOGY OF DIPHTHERIA
Diphtheria is typically a disease of communities, schools and households
with children of susceptible ages (Wilson and Miles, 1946). Closeness and
duration of contact play a major part in determining the spread of the
disease. Contact during sleeping hours in common dormitories is far more
dangerous than casual contact during waking hours (Christie, 1969).
When many clinical cases of diphtheria from an outbreak are admitted
to hospital, spread of the disease is chiefly due to carriers and/or, at present,
to asymptomatic cases of diphtheria, closely resembling simple cases of
tonsillitis (erythema, mild sore throat). According to Wildfuhr (1949) and
to our own experience, diphtheria bacilli are often detectable in the throat
during the incubation period and it is likely that early carriers might be
more dangerous than convalescent or healthy carriers, owing to the great
number of growing bacilli they carry. Observations made by Wright et al.
(1941) showed that dust is a possible source of infection in hospitals and
other institutions. Diphtheria bacilli in dust remain fully virulent for
as long as 5 weeks (Christie, 1969). C. diphtheriae has no intermediate
animal host, although virulent diphtheria bacilli have been isolated from
horses and monkeys.
Stsnicii et al. (1968) isolated C. diphtheriae in 14.7%, C. ulcerans in
7% and other corynebacteria in 35% of horses. The spread of diphtheria
by milk is an epidemiological curiosity. It usually spreads from ulcers on the
teats of cows with which the milkers (who may be diphtheria bacilli
carriers) come in contact. Diphtheria outbreaks are not as a rule explosive
in character but develop step by step, by human contact. The intensity of
infection is governed by the level of specific immunity of the population
and by the success of efforts to control its distribution by the rate spread
of the causative agent. One or two decades ago, in the epidemic period,
when mass immunisation was not so extensively applied, several outbreaks
were recorded in Romania. These normally resulted in 60-100 cases, with
approximately 25-30 contacts per case, each carrying the same phage type
as the index cases. At that time precise principles of surveillance and control
were established and were rapidly applied in order to limit an outbreak as
soon as possible (Saragea et al., 1965). Subsequently, with the application
of mass immunisation and thorough surveillance of the causative agent in
Romania (since 1965-1966), outbreaks have consisted of no more than five
to seven cases. During the last 5-6 years, when the general level of immunity is measured at 95-96% Schick negative reactors, only very rare
sporadic cases (one to two per year) occur throughout the country and no
more than five or six contacts per case are identified.
Phage typing led to marked progress in the follow-up of carriers and/or
A. SARAGEA ET AL.
VII. EPIDEMIOLOGY OF DIPHTHERIA
Diphtheria is typically a disease of communities, schools and households
with children of susceptible ages (Wilson and Miles, 1946). Closeness and
duration of contact play a major part in determining the spread of the
disease. Contact during sleeping hours in common dormitories is far more
dangerous than casual contact during waking hours (Christie, 1969).
When many clinical cases of diphtheria from an outbreak are admitted
to hospital, spread of the disease is chiefly due to carriers and/or, at present,
to asymptomatic cases of diphtheria, closely resembling simple cases of
tonsillitis (erythema, mild sore throat). According to Wildfuhr (1949) and
to our own experience, diphtheria bacilli are often detectable in the throat
during the incubation period and it is likely that early carriers might be
more dangerous than convalescent or healthy carriers, owing to the great
number of growing bacilli they carry. Observations made by Wright et al.
(1941) showed that dust is a possible source of infection in hospitals and
other institutions. Diphtheria bacilli in dust remain fully virulent for
as long as 5 weeks (Christie, 1969). C. diphtheriae has no intermediate
animal host, although virulent diphtheria bacilli have been isolated from
horses and monkeys.
Stsnicii et al. (1968) isolated C. diphtheriae in 14.7%, C. ulcerans in
7% and other corynebacteria in 35% of horses. The spread of diphtheria
by milk is an epidemiological curiosity. It usually spreads from ulcers on the
teats of cows with which the milkers (who may be diphtheria bacilli
carriers) come in contact. Diphtheria outbreaks are not as a rule explosive
in character but develop step by step, by human contact. The intensity of
infection is governed by the level of specific immunity of the population
and by the success of efforts to control its distribution by the rate spread
of the causative agent. One or two decades ago, in the epidemic period,
when mass immunisation was not so extensively applied, several outbreaks
were recorded in Romania. These normally resulted in 60-100 cases, with
approximately 25-30 contacts per case, each carrying the same phage type
as the index cases. At that time precise principles of surveillance and control
were established and were rapidly applied in order to limit an outbreak as
soon as possible (Saragea et al., 1965). Subsequently, with the application
of mass immunisation and thorough surveillance of the causative agent in
Romania (since 1965-1966), outbreaks have consisted of no more than five
to seven cases. During the last 5-6 years, when the general level of immunity is measured at 95-96% Schick negative reactors, only very rare
sporadic cases (one to two per year) occur throughout the country and no
more than five or six contacts per case are identified.
Phage typing led to marked progress in the follow-up of carriers and/or