In the 1990s, an epidemic of cholera caused by Vibrio cholerae 01 El Tor has spread from northern Pakistan to the Mediterranean. In 1993 sporadic cases of cholera, and epidemic foci, were recorded in many countries of the southern part of Eastern Europe. Cases were also notified in Crimea and Turkey, but only one imported case was notified in Greece (1).
On 9 September 1994, the Albanian government reported to the World Health Organization (WHO) an epidemic focus of cases of cholera by V. cholerae El Tor in the city of Berati, in the central- southern part of the country. An epidemiologist and a bacteriologist from the Istituto Superiore di Sanità in Rome were sent to Albania on behalf of the WHO regional office. This report presents the results of the outbreak investigation made in collaboration with colleagues from the Institute of Public Health of Tirana.
Cases of cholera were defined as patients who were admitted to hospital with severe diarrhoea (six or more loose stools in the previous 24 hours) and who met one of the following criteria: isolation of V. cholerae El Tor from stools; or clinical diagnosis of cholera in a patient from a town where patients had been diagnosed by the isolation of V. cholerae El Tor isolated from their stools.
Data were obtained from hospital registers, personal interviews with patients admitted to hospital, reports of the Albanian National Hygiene Institute, the bacteriology laboratory of the Albanian Hygiene Institute, and local health offices.
Following the isolation of V. cholerae from stool specimens or rectal swabs, isolates were identified and characterised by biochemical tests and serotyped with group and type specific antisera by the Institute of Public Health of Tirana and subsequently confirmed by the Institut Pasteur in Paris.Cytotoxicity assays were used to measure cholera enterotoxin production. Antimicrobial susceptibility was also tested.
Most cases were clustered in small towns in the south eastern Albania along the main roads from Northern Greece and the Former Yugoslavian Republic of Macedonia. There were no family clusters and only five child cases. The number of adults admitted to hospital with acute gastroenteritis in these towns reached a peak during the week 9 to 16 September 1994. In the hospitals of the two main coastal towns (Durazzo and Vlora) no similar peak was found.
The first six cases of cholera were diagnosed in Albanian refugees who had been repatriated from Greece a few days before becoming ill.
Over 100 patients with cholera were interviewed in three towns. No food stuff was identified as a potential risk factor, but all had drunk fresh water or been exposed to the public water supply. Thirty percent of those interviewed did not live in the towns, but came from neighbouring villages. These patients had been exposed to water in the town on the day of their visit, two to five days before becoming ill. There were few or no data from monitoring drinking water quality in the investigated towns. Colimetric counts showed evidence of heavy faecal contamination of the drinking water in districts where patients had been exposed.
More than sixty strains of V. cholerae isolates, representing different geographical clusters, produced cholera enterotoxin. All strains were resistant to tetracycline and trimethoprim-sulphametoxazole and were sensitive to nalidixic acid, cephalotin, chloramphenicol, gentamicin, ampicillin and tobramycin.
The epidemic caused by V. cholerae O1 El Tor quickly reached the Mediterranean Sea in the beginning of 1990. The Albanian outbreak showed that environmental risk factors for waterborne transmission of cholera exist in countries on the Adriatic coast.
Although no case-control study was done to indentify the vehicle of the outbreak, the evidence for waterborne transmission in the Albanian epidemic was strongly supported by the geographical distribution of cases, individual risk exposure of cases, and by colimetric counts that confirmed faecal contamination of drinking water. Interruption of the public supply of drinking water led to an abrupt halt of new cases of cholera. Given that most infected individuals are asymptomatic (2), the small number of child cases, and the lack of household clusters are consistent with the diffuse pattern of waterborne cholera.
Cholera may be transmitted from region to region or country to country by infected humans. Faecal contamination of the public water supply enabled explosive outbreaks of the cholera to occur in towns. Many of the affected towns shared the same water supply.
In early October 1994, 12 cases of cholera were diagnosed in Bari, an Italian port on the opposite coast of the Adriatic Sea to Albania. These 12 citizens had eaten raw squids washed with water from the Bari harbour. V. cholerae was also isolated from raw squid and samples of sewage water. The isolated vibrios were shown to be the same phage type as those found in Albania.
1. Cholera in 1993, Weekly Epidemiological Record, WHO, 14 July 1995; 70: 201-208
2. Benenson’s Control of Communicable Disease in Man, 15th edition, 1990, American Public Health Association