Arbovirus infections have always been important in PNG, and they have been given recent prominence as emerging infections. In addition to the widely endemic virus of Murray Valley encephalitis (MVE), Japanese encephalitis virus (JE) has been found in Western Province and along the south coast to Milne Bay; it is also spreading eastwards from Vanimo and Wewak on the north coast. Because of its association with pigs as an amplifying host, JE is likely to be much more dangerous to the people of PNG than MVE has been. Dengue is common and, disturbingly, a few cases of dengue haemorrhagic fever have recently been reported. The Institute's virology and entomology units combine to study these infections, in collaboration with colleagues from Queensland.

The Institute is the national centre responsible for the eradication of poliomyelitis and the certification of its eradication, and will continue this activity until these objectives have been successfully achieved.

A number of studies on cancer have been carried out. Burkitt lymphoma is a relatively common tumour in coastal children and Papua New Guinea has the only focus of the disease outside Africa. The immune responses to the causative Epstein-Barr virus and the relationship of the viral infection to malaria in both pregnancy and neonatal life have been investigated. New variants of the virus have been found in Papua New Guinea. Studies on another virus which causes lymphoma, human T-lymphotropic virus type I (HTLV-I), have also been undertaken in collaboration with colleagues overseas. The exact nature of the virus and its clinical importance in Papua New Guinea are still being determined but the isolation of the local variant of HTLV-I has advanced these studies considerably. This variant has also been found in Solomon Islanders and Aboriginal Australians and is significantly different from the cosmopolitan strain found globally. Hepatoma is a common cancer of adults in Papua New Guinea, especially in the highlands, and it is also caused by a virus, the hepatitis B virus. Since newborn transmission is believed to be critical for the development of adult hepatoma, vaccination with a hepatitis vaccine should begin at birth. Naturally acquired immunity to hepatitis B virus and the likely ways the virus is transmitted have been studied in Tari. Cancer of the mouth and of the cervix are the two leading cancers in PNG and among the factors involved in their causation are different strains of human papillomavirus (HPV). The prevalence of HPV infection and the genetic typing of the viruses are being investigated in a joint study with the Department of Pathology, University of Papua New Guinea.

Research was conducted on tinea imbricata, or grille, a disfiguring fungal skin infection, with emphasis on the role of host factors in determining susceptibility to the disease. Bacterial skin infections are a major cause of morbidity in all communities in Papua New Guinea and studies of their aetiology have been carried out; particular attention was given, in collaborative projects, to tropical ulcer and yaws, which are still significant public health problems in certain areas. Collaborative studies were also carried out on leprosy in the Karimui area.

Studies on arthritis have established the importance of reactive arthritis as a common disease and its genetic association with HLA-B27. Further work is required to determine the infections which initiate the process of reactive arthritis.

Anaemia is a widespread condition in Papua New Guinea; it causes significant morbidity in itself and may predispose to serious infection and death. It may be caused by nutritional deficiency, in particular of iron, or infection, in particular malaria and hookworm. The effect of an intervention giving a low dose of intramuscular iron at two months of age on the incidence of serious infection during infancy was investigated in Madang; it was shown that correction of iron deficiency in infants increased malaria rates and effects. The effect on morbidity was not confined to malaria. There were 38% more admissions for Severe Lower Respiratory Infection in the iron group and 56% more time was spent in hospital with SLRI by infants in the iron group. Morbidity rates for other non-malarial infections showed the same effect and there was evidence that this was demonstrated in 80% of the cohort and this factor was protective both against malarial anaemia and the deleterious effects of iron. This result was followed up with a double-blind study carried out in schoolchildren given oral iron supplementation; in this case there was no associated increase in malaria.

In its early days the Institute undertook a major program on goitre and endemic cretinism, for which iodized oil was used and promoted. More recent studies on endemic cretinism have found a few remote areas with little goitre but new cases of cretinism. Further studies on iodine status would be of interest but the findings have emphasized the need for the required iodine levels in salt to be enforced by the Department of Health. This should be sufficient to prevent the incidence of iodine deficiency disorders in nearly all parts of PNG.