28. Virological investigation of the disease is maintained on a routine and year-round basis. A poliomyelitis faecal survey in normal children aged under 5 years was carried out in June and July. No excretion of 'wild' poliovirus was found. Vaccine strains of poliovirus were found in 1.5% of the children.
Influenza
29. The notification of influenza is entirely voluntary. The Virus Laboratory continued to function as a World Health Organization National Influenza Centre and virological investigations of throat swabbings and throat washings are continued on a year-round basis.
30. An outbreak of influenza was observed in the period between 9th July and 12th August with maximum intensity in the latter part of July. The disease, though clinically mild, was widespread in the com- munity involving people of all age groups. As far as could be determined some 10% of the population was affected but the case fatality ratio was very low indeed. The strain of virus isolated and responsible for the outbreak was identified as a strain of influenza virus Type A2 showing a considerable antigenic shift from strains of this virus occuring in recent years. The identification was subsequently confirmed by the World Health Organization International Influenza Centre and the strain named as A2/Hong Kong/1968. In the autumn, winter and spring of 1968-69 it caused outbreaks of influenza, popularly called "Hong Kong 'flu' in various parts of the world. There is no reliable evidence that the strain actually originated in Hong Kong though it was of course first isolated here. No evidence of this strain has been found among local residents since September, 1968.
Tetanus
31. This disease, although not notifiable, is recorded with reasonable accuracy owing to the severity of the symptoms requiring hospitalization of clinical cases. In past years, approximately half the cases reported were in new-borns whose birth had not been attended by trained personnel and who had been exposed to various hazards from unsterile materials. In 1968 tetanus neonatorum was responsible for only 17% of the recorded cases and infant mortality from such infection fell from 1.2 deaths per 1,000 in 1951 to 0.036 deaths in 1968.
Viral Hepatitis
32. Notification of this disease is not compulsory, but the number of patients treated for it in hospital had shown a steady decline since
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1966, when there were 386 cases treated as compared with 218 in 1967 and 191 in the year under review. Since August, 1966, disposable syringes have been used in all mass immunization drives and it would appear that their use has led to a reduction in the incidence of this disease.
33. Developments in certain other communicable diseases will be reviewed later in this report, while the remainder showed little varia- tion during 1968 and hence require no comment.
III. WORK OF THE HEALTH DIVISION
AREA HEALTH WORK
34. Much of the work of the area Health Officers, apart from their duties with the Urban Services Department in the maintenance of satisfactory standards in environmental sanitation and food hygiene, has been recounted in the preceding paragraphs on Epidemiology. Such work included not only the field investigations into the major communicable diseases but also the co-ordination of the activities of teams of inocu- lators participating in prophylactic immunization drives. Five such drives were staged during the year and reference has already been made to four, namely, cholera, poliomyelitis, diphtheria and measles. The fifth, promoting smallpox vaccination, was held in February, 1969. The increasing importance of Hong Kong in international travel by sea and air and the prevalence of smallpox in nearby countries underline the need to maintain a high level of community protection against the disease.
TUBERCULOSIS
(Sec tables 17-23)
35. As stated previously, tuberculosis is the major health problem of Hong Kong. The policy for control of the disease has been to protect, by vaccination with B.CG., the new borns, who are particularly vulner- able to the fulminating forms of the disease, and the primary school entrants who may develope active disease later in life. For actual cases of the disease, it has now been shown that in a large proportion of cases out-patient therapy is at least as good as institutional treatment. The not inconsiderable institutional resources are reserved for those not responding to out-patient therapy, for acutely ill cases, for those where the diagnosis is in doubt and for those in need of surgical intervention. In the execution of this policy there has been a high degree of co- operation between Government and voluntary agencies concerned with
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