Coxsackie A9 virus outbreak in Northern Ireland during 1970.

MATERIALS AND METHODS Faeces, CSF, throat swabs and acute and convalescent sera were obtained from aseptic meningitis cases, while faeces and/or throat swabs were obtained from other cases. Primary rhesus monkey kidney cell cultures were used for virus isolation and isolated viruses were typed with Coxsackie A9 neutralizing serum supplied by the Standards Laboratory, Central Public Health Laboratory, London. Acute and convalescent sera from aseptic meningitis cases from whom virus had not been isolated and who were negative when screened serologically in the complement fixation test against mumps, measles, herpes simplex, lymphocytic choriomeningitis and louping ill viral antigens were tested for Coxsackie A9 virus neutralizing antibody. Sera were inactivated at 56°C. for 30 minutes then serial dilutions were mixed with equal volumes of 200 TCD50 of Coxsackie A9 virus which had been isolated from the CSF of a patient in the current outbreak. The virus-serum mixtures were left for 2 hours at 37°C. before inoculation.