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ably lower than in the preceding year. In these circumstances the number of infants and children immunized cach year is not sufficient to bring the disease under satisfactory control.

110. The routine investigation of notified cases and their contacts was carried out by the Health staff and resulted in the discovery of 29 carriers.

Measles

111. Cases reported during the year numbered 786, showing a drop of 89 or 10.2% as compared with the preceding year.

112. The number of deaths attributed to measles was unusually high, namely 191, giving a case fatality rate of 24.3%. Corresponding figures for 1957 were 93 deaths and 10.6%. The recorded death rate from measles is unduly high because of the many mild cases which are not notified and the late admission of cases with complications. such as broncho-pneumonia, to hospital.

113. The infection was most prevalent in the second and fourth quarters of the year. Outbreaks were observed in institutions and schools.

Poliomyelitis

114. The notifications of acute paralytic poliomyelitis rose sharply during May and June, reaching the highest monthly totals ever recorded of 53 in May and 82 in June. There was a decline in July and August with a rapid fall thereafter. A spot map of the occurrence of notified cases showed a fairly even and sporadic distribution throughout the whole Colony. All told, 262 cases were notified compared with 45 during the previous twelve months; 41 deaths were registered giving a case fatality rate of 15.6%. There were 13 non-Chinese cases and amongst the Chinese population affected 66.3% of all cases occurred in the 0-1 age group; amongst the non-Chinese cases the incidence was highest amongst adults with a case fatality rate of 43%. The overall incidence was 9.53 cases per 100,000 of population with a mortality rate of 1.5 per 100,000. As was expected a type 1 virus proved to be responsible.

115. There was naturally considerable public anxiety and a demand for a mass vaccination campaign throughout the Colony. Investigation revealed however that during previous years the number of infants brought to the physiotherapy clinics for treatment of paralysed limbs of recent onset greatly exceeded the number of cases of the disease

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notified. This indicated the possibility of cases not being diagnosed in the acute stage of infection and it appeared probable that much of the increase in notification during 1958 may have been due to a more general awareness of the disease, better and carlier diagnosis and an increased appreciation of the benefits of early hospital treatment and physiotherapy. Taken in conjunction with the distribution of cases notified throughout the Colony it seemed certain that there was not in fact a greatly increased incidence over previous years but that many more cases were being diagnosed early and admitted to hospital during the acute slage.

116. The question of using a Salk type vaccine on a mass scale was given the most careful consideration. The use of this vaccine as a control measure during periods of peak incidence has not proved to be effective; the significant protection of the most vulnerable age group of 0-4 years could be expected to be ensured only over a period of several months, Even then success depends on the full co-operation of parents to ensure that the initial and "booster" doses are given to schedule, Experience with diphtheria and typhoid inoculations in the Colony has shown that this essential co-operation is not forthcoming when more than one injection has to be given.

117. An oral type vaccine of proved efficacy was not available for general use at that time and was still largely in the experimental stage when it could not be released for use for mass vaccination without significant risk unless applied under the most carefully controlled con- ditions. Later in the year, the outbreak of poliomyelitis in Singapore presented an opportunity to gain experience of the use of the Sabin oral vaccine administered under controlled conditions during an epidemic. Administrative and laboratory staff were seat to Singapore to gain experience of the organization and laboratory techniques in use. There- after plans were made to establish a Poliomyelitis Virus Unit in Hong Kong so that the use of an oral vaccine, either during an epidemic or as a purely preventive public health measure, would be under adequate laboratory control, Equipment is on order, trained medical and techni cian staff are now available and the unit is to be established within the University Department of Pathology at the Queen Mary Hospital.

118. The general immunity against poliomyelitis in Hong Kong is high. The following table sets out the results of biological investigations carried out in 1956.

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