Cholera Outbreak in Donetsk Oblast, Ukraine, in 2011

  Published: 10.01.13 Updated: 10.01.2013 12:15:31

V. Liashko
State Sanitary and Epidemiological Service of Ukraine, Kiev

Citation: Liashko V. Cholera Outbreak in Donetsk Oblast,Ukraine, in 2011. EpiNorth 2012;13:117-20.

In 2011, during the outbreak of cholera in Donetsk oblast, there were 33 patients with cholera and 24 vibrio carriers with isolated V. cholera El-Tor serovar Оgаwа in clinical specimens registered from May 29, 2011 to September 9, 2011.

Cases of cholera were first registered in Ukraine since 1970. From time to time there were reported outbreaks of the disease. The outbreaks were primarily caused by virulent cholera vibrio and, as a rule, were imported from endemic areas in Ukraine. Major outbreaks of cholera were reported in 1970 (in Kerch and Odessa), in 1971 (in Donetsk and Kherson), in 1991 (in Nikolaev and the settlement of Nizhniye Serogozy), in 1994 (in Simferopol and Nikolayev, with 22 lethal outcomes) and in 1995 (in Nikolayev) (3).

In some water basins in Ukraine, the regular circulation of avirulent cholera vibrio is observed. This indicates that the environmental conditions are favorable for cholera vibrio survival, including virulent variants, when those appear in the waters. In Mariupol, a city in Donetsk oblast, there is also annual circulation of avirulent vibrio of serogroup О1, biovar El-Tor.
In 2011, there were clustered cases of cholera registered in the city of Mariupol. The purpose of the article is to describe this cholera outbreak.

In order to localize the focus of cholera, on May 29, 2011 a meeting of the emergency committee was held in Mariupol. As a result of the meeting, it was decided to establish a strategic headquarters and to implement a plan for the localization and elimination of the cholera focus.
In accordance with the plan, the following emergency measures were taken:

- swimming and private fishing were prohibited on the coast of the Azov Sea as well as in the Kalchik and Kalmius rivers (thus recreational use of water was taken under control);
- the disinfection of drinking water was intensified: in the water supply system filtering stations and in the biological treatment stations for household water sewage, chlorine and other reagents were added in stock sufficient for 30 days of treatment;
- the condition of sanitary control zones for water supply sources and major water pipes were checked as well as the condition of water supply and sewage networks and water conduit wells;
- the range of food dishes permitted for sale in public catering establishments was reviewed: the production of all potentially epidemiologically risk food dishes was prohibited;
- all restaurants serving fish dishes, sushi and similar products were checked for compliance with epidemiological norms;
- the sale of any kinds of fresh, dried, salted and smoked fish was prohibited in the city markets without refrigerators; the conditions of fish trade in the city markets were subject to epidemiological control;
- the ballast water drain from the sea ships was taken under intensive surveillance;
- the incidence of the disease was described in detail every day on the basis of emergency reports received by the state sanitary and epidemiological service of Donetsk oblast from the health department of the city administration.

From May 29, 2011 to September 9, 2011 there were 33 patients with cholera and 24 vibrio carriers registered in Donetsk oblast. V. cholera El-Tor serovar Оgаwа with toxin-producing genes was isolated in clinical samples.
On the first day, 8 patients (25%) seeking medical care visited health institutions; 8 people (25%) on the second day, 5 people (15.6%) on the third day and 11 people (34.4%) on the fourth day and later visited the institutions. The last vibrio carrier was registered on August 12, 2011 and the last case of cholera was reported on August 19, 2011. The incidence of the disease (including cases of vibrio carriers) was 10.8 per 100,000 population and at the time of the patients’ first visits cholera infections accounted for 5.2% of acute intestinal diseases during the period of the focus activity.
The age of patients and vibrio carriers ranged from 1 year to 90 years. Among children under the age of 18, there was 1 case of cholera and 3 vibrio carriers registered (5.1 per 100,000 population). The highest incidence was reported among the age groups of 40-49 years (16.6 per 100,000 population) and 50-59 years (14.2 per 100,000 population). The share of people over the age of 40 among all cholera patients and vibrio carriers was 65%. There were more men (57.4%) than women (42.6%) among cholera patients and vibrio carriers. Thirty patients and vibrio carriers (55.6%) were unemployed adults, including 11 retired persons (20.4%), 3 disabled people (5.5%), 3 people from socially marginalized groups (5.5%) and 4 homeless people (7.4%). Twenty people were employed adults (37%). There were also 3 children (5.5%) who did not attend school and one secondary school pupil (1.8%).

During the period of focus activity, a combination of infection transmission factors was revealed including:
- sea water: 7 people (13.0%), ingestion or swimming;
- river water (in the Kalchik and Kalmius rivers)
- 6 people (11.1%), swimming or fishing and 1 patient who drank water from the river;
- brook in Ozernaya Street: 2 people (3.7%);
- process water: 2 people (3.7%);
- fish: 26 people (48.1%); crucian carp and European carp, 17 people (65.4%); goby, 8 people (30.8%); ablet, 1 person (3.8%);
- person-to-person transmission: 6 people (11.1%), including 1 patient infected through a contact at work (1.9%);
- unidentified infection source: 5 people (9.3%).

The first three cases of cholera were registered prior to the start of the epidemic season on May 29, 2011. In one of the cases the probable source of infection was sea water, while in the other two cases people fell ill after eating goby caught in the Azov Sea.
Cases of cholera were registered in all the four districts of the city of Mariupol. The maximum number of patients and vibrio carriers (28 cases) was registered in Oktyabrsky district (15.8 per 100,000 population) and 17 cases in Ilyichevsky district (14.1 per 100,000 population). The minimum number of cases (6 cases) was reported in Ordzhonikidzevsky district (4.9 per 100,000 population) and 3 cases in Primorsky district (4.4 per 100,000 population). Oktyabrsky and Ilyichevsky districts are located closer to the Kalchik and Kalmius rivers, and therefore the larger number of cases in these districts is probably because the population is actively in contact with the rivers. In addition, these areas is more deprived.
In the city of Mariupol from May 29, 2011 to August 29, 2011, 3670 objects of epidemiological risk were checked and 2037 violations of sanitary legislation were registered, which resulted in temporary closure of 162 objects. The sale of 1096 kg of epidemiologically risk food products (based on the results of bacteriological testing) was prohibited and 370 employees were dismissed because they had not reported for timely occupational medical screening. Sanitary and bacteriological analysis was performed on 21,851 samples from environmental objects including 4609 samples of drinking water, 2522 samples of water from the sea and open basins, 2562 samples of food products (with 331 samples of fish and seafood).
A total of 3232 samples from various environmental objects were tested for cholera including 1271 samples of sea water, 359 samples of river water, 105 samples of water from other natural basins, 432 samples of sewage water and 245 samples of fish and others. Thirty five cultures of cholera vibrio О1 biovar El-Tor revealed 31 strains of virulent cholera vibrio of serogroup О1 biovar El-Tor serovar Ogawa, 2 strains of avirulent cholera vibrio of serogroup О1 biovar El-Tor serovar Ogawa and 2 strains of avirulent cholera vibrio of serogroup О1 biovar El-Tor serovar Inaba.
Virulent strains were found in 4 samples of sea water, 5 samples of fresh water (2 water samples from the Kalmius river, 1 water sample from the Kalchik river, 1 water sample from the Pavlopolskoye reservoir and 1 water sample from the brook), 5 samples of sewage water, 3 samples of fish, 1 sample of hydrocoles (shrimps), 1 sample of processed water, 2 samples of industrial sewage water and 10 samples from washouts and collector plugs in the sewerage system. The suspected sources of infection for patients and vibrio carriers were confirmed by results of laboratory tests performed on samples taken from the environment objects.
Each case of cholera and each vibrio carrier state was subject to timely epidemiological investigation. A total of 2775 people were screened including 981 patients with acute intestinal diseases and 1794 healthy individuals. The group of healthy individuals included 734 contact (a virulent strain of cholera vibrio of serogroup О1 biovar El-Tor serovar Ogawa was found in 22 contacts), 460 decreed professionals (including 72 employees of sewage stations, 6 drivers of cesspool cleaning cars, 180 fishermen, 6 fishing inspectors, 61 market traders selling fish and other types of food in the city markets) and 655 people from socially marginalized groups including 360 homeless people within 37 foci. All cases were hospitalized in isolation wards. Their contacts received emergency prevention treatment with antibiotics, and disinfection of the cholera foci was performed.
During the epidemic period in Donetsk oblast, 92% of cesspools and outhouse toilets in the private sector on the coast of the Azov Sea and on the banks of the Kalchik and Kalmius rivers were disinfected. A total of 552 cesspools were pumped and disinfected. Numerous cases of non-sanctioned discharge of household sewage into the rainwater disposal system were detected and plugged. In the settlements of Gavan and Slobodka, rainwater disposal channels were cleared and disinfected.

In accordance with data from the Ukrainian Plague Control Station, the outbreak of cholera in Mariupol in the summer of 2011 took place because virulent strains of cholera vibrio were imported from endemic territories by tourists. The data was supported by the biological characteristics of isolated strains and the detected routes of import by seamen, tourists and students.
It was possible to make this conclusion because there was no large-scale cholera epidemic in the city of Mariupol. There were multiple sporadic cases of the disease registered in Mariupol and the outbreak did not spread outside Donetsk oblast. There were no lethal outcomes of the disease reported. The epidemiological measures implemented would have been more effective if all counter-epidemic events had been conducted in order to localize and eliminate the focus of cholera in Mariupol.
The current epidemiological situation for cholera in Ukraine is under control. There have been no cases of the disease registered in 2012. This proves that specialists from the sanitary and epidemiogical service together with responsible representatives of local authorities have managed to take effective and timely measures in order to prevent cholera epidemic through drinking and processed water, food and the use of recreation sites.

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