Echovirus type 4 outbreak in Northern Ireland during 1970-71.

AN extensive outbreak of Echovirus type 4 took place during 1970-71 in Northern Ireland. Echovirus type 4 is not only a rare virus to isolate from patients but this was also the third major enterovirus outbreak in Northern Ireland during the past four years. The olther outbreaks were associated with Echovirus type 6 during 196;8 (Connolly and O'Neill, 1970) and Coxsackie A9 virus during 1970 (Connolly and O'Neill, 1971). MATERIALS AND METHODS Faeces, CSF, throat swabs and acute and convalescent sera were obtained from patients with aseptic meningitis while faeces and/or throat swabs were obtained from other cases. Primary rhesus monkey kidney cell cultures were used for virus isolation. At the beginning of the outbreak the first virus isolates could not be typed using the Echovirus diagnostic serum pools supplied !by the Standards Laboratory, Central Publ;ic Health Laboratory London. Tle first virus isolates were typed using an Echovirus type 4 (strain Pesascek) neutralising antiserulm from Microbiological Associates Inc. which was not included in the Echovirus diagnostic serum pools. It was found that the Echovirus type 4 (strain Du Toit) neutralising antiserum supplied by the Standards Laboratory when used at the recommended dilution of 1: 640 would not neutralise our isolates, but worked satisfactorily when used at a final dilution of 1: 40. Acute and convalescent sera were available from 62 patients from whom virus was not isolated and who had aseptic meningitis during the period of the Echovirus type 4 outbreak. Thei convalescent sera were tested at a final dilution 1: 20 against 100 TCD50 of Echovirus type 4 (strain Du Toit) in a four hour neutralisation test at 37°C. and the acute and convalescent sera of those which had antiibody were then titrated. The sera from all asept-ic meningitis patients were also tested for rising titres of antibody against mumps, measles, herpes simplex, louping ill andi lymphocytic choriomeningitis viral antigens using the overnight complement fixation test at 4°C. (Bradstreet and Taylor, 1962).