|* One patient was tested with Latex and ELISA.
epidemic curve had no distinct peak (figure) but the largest number of cases developed
symptoms in early August. The incidence of cases has decreased since mid September.
Ninety-one per cent (161) of cases of amoebiasis lived on the left side of the River
Kura, and cases who did not live there worked in this area. Attack rates by district of
Tbilisi ranged between 3 and 42 per 100 000 inhabitants. The highest attack rates were
close to a water filtration system that used surface water from a large lake and all
districts with attack rates exceeding 15/100 000 were fed by this source. At this water
treatment works the filters were of poor quality and routine maintenance was not
documented. Districts with lower attack rates were fed by ground water.
In Tbilisi as a whole, between 600 and 700 breakdowns of the water supply and sewerage
system were reported between April and September 1998, but the routine Escherichia coli
index in drinking water, investigated by two different laboratories, was never reported to
be significantly increased. No previous problems with the water treatment works had been
reported. All water samples investigated at the ISS were negative for cysts.
The mean age of probable and confirmed cases with liver abscess was 49 years (median
47, range 7-79). Eighty four per cent (88/106) of them were males, and 30% (19/63) of
cases with liver abcess and of whom information were available (63) did not report
previous abdominal symptoms. All patients with liver abscess were admitted to hospital and
treated with intravenous metronidazole for three days, followed by oral metronidazole and
doxycycline for 11 days. Four patients with liver abscess died (case fatality rate 3.8%).
Cases of intestinal amoebiasis were nearly equally distributed between the sexes and
their mean age was 41 years (median 42, range 3-79). Patients with severe intestinal
disease were treated in the same way as those with liver abscess but patients with mild
intestinal disease were treated with oral metronidazole. Chloroquine was given for 20 days
to eliminate carriage of cysts. No other drug for treatment of cyst carriers was licensed
Since 10 August the public has been advised to boil tap water before drinking, although
routine tests for E. coli in the water never showed significant elevation. On 23
August, control measures were taken at the water filtration station. The dosage of
aluminium sulphate for coagulation was increased, residual chlorine was increased from
0.3% to 0.7% before filtration, the duration of back washing was increased, filters were
thoroughly cleaned, and the filtration speed was reduced. The second chlorination,
performed after the water treatment works and before the water is distributed to the pipe
system, was also increased. At the end of August, Russian hydrobiology experts were
invited to investigate the different sources of drinking water supply, but no cysts of
E. histolytica were detected. The number of cases has decreased since September, but
the incidence has not fallen to zero.
Descriptive epidemiology is the major tool for an assessment and in the current
outbreak it was suitable to formulate the most likely hypothesis about transmission. The
unusually high incidence of cases of amoebiasis and their geographical distribution
suggested a waterborne outbreak from a common source. The local situation in Georgia did
not allow an epidemiological analytical study to be performed during the assessment.
Our hypothesis is that either faecal contamination had happened after the water
treatment works or the filtration process had been inadequate. The second chlorination
could have made the levels of other pathogens so low as to be undetectable. The high
proportion of cases presenting with liver abscess suggests either that the strain was very
invasive or that the population was very susceptible. Cases with intestinal disease are
likely to have been grossly underreported before medical care was offered free of charge
and the public was informed.
Other sources of infection, such as food and drink and transmission by flies, were
considered by local authorities but are unlikely to have been responsible for the
outbreak. Ensuring quality standards in the drinking water and sewerage systems is crucial
to prevent continuing transmission and further outbreaks. Treatment processes should be
applied rigorously and documented, and water quality monitored against standards if we are
to minimise the risk of such large scale outbreaks.
Furthermore, clear protocols for plans of action must be formulated in the event that
cases continue to occur or cysts continue to be detected in the drinking water supply.
Meanwhile amoebiasis should be made notifiable and incidence of disease documented in the
whole country. Screening facilities for asymptomatic carriers should be easily accessible
to the public and carriers should be treated.
Further reports from the GNCDC have shown that the incidence has decreased but cases
are still occurring in Tbilisi. The wide variation in incubation period will make it
difficult to estimate the actual period of infection and, in addition, secondary cases are
expected to occur. National notification data suggest that 1377 cases of intestinal
amoebiasis and 365 cases of liver abscess arose in Tbisili between July 1998 and June
1999, and that numbers have declined since September 1998 (P Imnadze, director of GNCDC,
personal communication). In June 1999, 35 cases of intestinal amoebiasis and 13 of liver
abscesses were notified.
Analytical epidemiological studies, which have been carried out by the GNCDC and the
Centers for Disease Control and Prevention, Atlanta since the assessment, may help to
identify the risk factors in the continuing cases, and thus provide the information
necessary to guide prevention.
It is unlikely that all problems related to the sewerage and drinking water systems
will be solved in near future despite the efforts made by the local authorities. An
increased risk of acquiring amoebiasis in Tbilisi may be present for several years and
amoebiasis due to E. histolytica should be considered in travellers to Georgia.
Amoebiasis is rarely reported in western Europe and included in statutory notification
systems in only six countries (Austria, Belgium, Luxembourg, Norway, Portugal, and Sweden)
We would like to thank all the people who
contributed to this investigation, namely Gia Arbolishrili and Guliko Namoradze, Municipal
Public Health Office, Eteri Botsvadze, Department of Infectious Diseases of the Medical
University, Ramaz Urushadze, Department of Public Health, Merab Iosava, GNCDC, Nicholaz
Shavdia, Michael Kurchuli, and David Gagua, State Sanitation Department, Iusa Tsartsidze,
water supply company, Avtandil Jorbenadze and Amiran Gamkrelidze, Ministry of Health.
Furthermore, we would like to thank Rusiko Klimiashiili for her support and translating,
M. Scamiccia for serological and parasitological investigations, Marta Ciofi degli Atti,
Olivier Ronveaux, Stefania Salmaso, Mike Rowland, and Alain Moren for their critical
* EPIET, a programme funded by DGV of the commission
of European Communities.