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| EPI-NEWS |
National surveillance of communicable diseases
Dept. of Epidemiology
Editor: Susanne Samuelsson |
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| Tel.: +45 3268 3038 - Fax: +45 3268 3874 |
| epinews@ssi.dk - ISSN: 1396-4798 | |
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| VEROTOXIN-PRODUCING E. COLI (VTEC) 2001-2002 |
Infection with verotoxin-producing E. coli (VTEC) is a frequently occurring zoonosis, EPI-NEWS 9/03. VTEC causes gastroenteritis, often in the form of bloody diarrhoea. The most serious complication of VTEC is haemolytic uraemic syndrome (HUS).
Notified cases
In 2001, 93 cases of VTEC infection were notified to the Department of Epidemiology. Of these, six were complicated with HUS. In 2002, 128 cases were notified, two of which also had HUS. In addition, in 2001 two patients were notified with clinical HUS, and a further two in 2002. One of the patients in 2001 died.
Laboratory-diagnosed cases
The number of notified cases of VTEC, especially non-O157, is still increasing, Fig. 1. There were 87 and 137 (2.6 per 100.000) recorded cases in 2001 and 2002 respectively. The incidence is similar to that of Shigella infection (139 cases) in 2002.
In 2001-2002, 89 (40%) of the patients were children under 5 years of age. Among patients over 40 years, there was a predominance of females (78%). As in previous years, there was seasonal variation, with most cases occurring in summer.
Laboratory diagnosis
Laboratory diagnosis of VTEC is carried out either by slide agglutination of suspected colonies with a panel of OK antisera or by using DNA probe diagnostics. DNA probe diagnostics is performed primarily in the counties of Aarhus, Funen, Frederiksborg, Storstrøm, Bornholm and Roskilde, and in the municipalities of Copenhagen and Frederiksberg. The incidence was higher in the counties that use DNA-based diagnostics, table 1. However, there was great variation between all counties.
In the period 2001-2002, a total of 228 isolates from 224 patients were
characterised, table 2. The most commonly occurring serotype was O157:[H7]. Five different types of non-O157 O-groups together made up 45% of those characterized.
Symptoms
A total of 28% of the patients had bloody diarrhoea. Among those identified with O157, 55% had bloody diarrhoea. Of the 53 patients admitted to hospital, eight (15%) had HUS; O157 was isolated from two (25%), and non-O157 from six (75%): O26 (2), O111, O121 and O149 (1 each), and one patient had both VTEC O145 and O21. With the exception of one patient aged 7 years, all patients with HUS were under 3 years of age. In nine people travelling abroad to Asia, Africa and Cuba, a special travel-associated VTEC type O117:K1:H7 was identified. This type seems to cause persistent gastroenteritis.
Sources of infection
VTEC is found primarily in ruminants, from which it may spread to foodstuffs and the environment, including water. Because of the low infectious dose, VTEC is also transmitted by person-to-person spread.
In 2001-2002, 18% of the patients had acquired the infection during foreign travel.
Twelve family outbreaks were recorded in this period. In nine families, two people were infected with the same VTEC strain. In one family with proven O157, one of the children developed HUS. In three families, the strains of VTEC had different O types. In one other family, two brothers were infected, with VTEC O26 and EPEC O26, respectively.
Hygienic precautions and management of long-term carriers
To reduce the risk of secondary infection, particularly in institutions, it is important to follow the National Board of Health's guidelines (no. 61 of 14 April 2000) concerning persons resident in child-care institutions, those associated with nursing homes or hospitals, or who work in the food industry.
For asymptomatic excretors of VTEC, these guidelines may have consequences in terms of work and social circumstances. For this reason, in selected cases, antibiotic treatment of VTEC may be attempted in healthy long-term carriers. The treatment should only commence after individual assessment in consultation with the doctors at the Department of Gastrointestinal and Parasitic Infections (SSI), and after characterisation of the bacteria strain involved. Treatment in the acute phase of illness is contraindicated, as antibiotic treatment during the illness may increase the risk of HUS.
Case-control study
To gain greater knowledge of sources of infection and risk factors, SSI and the Danish Zoonosis Centre commenced a two-year case-control study on 1 May 2003. In connection with this, all patients with verified VTEC infection will be invited to take part in a questionnaire survey.
(Fl. Scheutz, K. E. P. Olsen, Dept. of Gastroint. and Parasitic Infections,
G. Høy Kock-Hansen, Dept. of Epidemiology)
21 May 2003
Also in this issue:
Patients with selected individually notifiable diseases, 1st quarter of 2003
Patients with other individually notifiable diseases, 1st quarter of 2003
Patients with laboratory-diagnosed RSV and rotavirus infections, 1st quarter of 2003
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