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Biomedical subjects

Y C Chan

Publications and source records attributed to Y C Chan.

At least 109 records · Page 6Linked to original sources
PubMed1987

Haemorrhagic fever with renal syndrome involving the liver.

A case of haemorrhagic fever with renal syndrome that originated in Malaysia is reported. The patient presented with clinical symptoms which were not typical of the disease as seen in endemic regions. Renal involvement, which is characteristic of haemorrhagic fever with renal syndrome, was mild, and the predominant symptom was a persistently marked elevation of serum transaminase levels that was suggestive of hepatitis. Liver involvement has not been described in the Asian form of haemorrhagic fever with renal syndrome. The patient developed a petechial skin rash and had severe thrombocytopenia. Serological confirmation of the diagnosis of haemorrhagic fever with renal syndrome was obtained by the demonstration of significant antibody rises to hantaviruses in the patient's acute- and convalescent-phase sera.

Adult↗
PubMed1987

Haemorrhagic fever with renal syndrome: clinical, virological and epidemiological perspectives.

Haemorrhagic fever with renal syndrome (HFRS) is caused by a group of RNA viruses within the family of Bunyaviridae known as hantaviruses. The classical, severe form of HFRS is characterized by fever, headache, abdominal and lumbar pain, proteinuria, haemorrhagic phenomena, shock and renal failure. The disease is associated with the prototype Hantaan virus and occurs in rural areas of Korea and China with Apodemus mice as reservoir hosts. A clinically less severe form of HFRS, which is caused by Seoul virus, occurs in urban areas with the house rat Rattus novegicus as the main reservoir host. The disease in nonendemic areas may be atypical and patients with symptoms the hepatitis and minimal renal involvement have been observed in Malaysia. Outbreaks of HFRS in humans involving infected laboratory rat colonies have occurred in several medical centres in various countries. Hantaviruses cause a chronic, asymptomatic infection in rodents which excrete the virus in their lungs, saliva and urine. Man becomes infected mainly by inhalation of infected droplets from healthy rodent carriers. Seroepidemiological studies using mainly the indirect immunoflourescent antibody test of sera from humans and rats showed that hantaviruses have a worldwide distribution.

Animals↗
PubMed1987

Epidemiological aspects of an outbreak of dengue fever/dengue haemorrhagic fever in Singapore.

A nation-wide outbreak of 260 cases of DF/DHF with 1 death occurred in Singapore from Apr-Sept 1986. The outbreak originated from 3 separate foci of transmission at the western, south-eastern and north-eastern parts of the island and then spread to other dengue receptive urban and suburban areas. The morbidity rate was highest in young male Chinese adults between 15 and 24 years of age. The outbreak was rapidly brought under control through destruction of adult Aedes mosquitoes, surveys and source reduction of larval breeding habitats, health education and to a certain extent law enforcement. The Aedes population was high in the main foci of transmission although the overall house index was only 1.1. Other factors which could have precipitated the outbreak included waning herd immunity of the human population and continuous introduction of dengue virus into the country.

Aedes↗
PubMed1985

Analysis of intraocular lens power calculation.

We performed an analysis of ocular biometry and intraocular lens (IOL) power calculation on 100 eyes that had anterior chamber IOL implantation during 1981 and 1982. Various methods of calculating the IOL power were used, including the standard lens power, presurgical basic refraction, Fyodorov's formula, Colenbrander's formula, Binkhorst's formula, and the SRK formula. In addition, we took the median value of these calculated results as the median power in selecting an appropriate IOL power. The postoperative refraction and actually implanted IOL power were used to determine the IOL power needed for emmetropia. Our regression analysis of the predicted IOL power and power actually needed for emmetropia showed that the methods of standard power and presurgical basic refraction were unreliable while the rest were of satisfactory accuracy. Among the latter, all the predicted IOL powers based on the biometric data had almost the same coefficient of determination and standard error of estimate. However, with the SRK formula and the median power the values of the regression line were closest to the ideal value. With the regression analysis, the accuracy of predicted IOL power from theoretical formulas was comparable to that of the SRK regression formula.

Aged↗
PubMed1985

The use of the single radial haemolysis technique in the serological diagnosis of dengue and Japanese encephalitis virus infections.

The single radial haemolysis test for the serological diagnosis of suspected dengue and Japanese encephalitis virus infections uses crude virus antigens with a haemagglutinin titre of 1:320 or 1:640. The results, which may be read 3 hours after the addition of a patient's serum, showed a general agreement between this test and haemagglutination-inhibition tests in the number of case diagnoses that were confirmed. The antibody responses of individual patients shown by the two tests, however, were different, which suggests that the two tests may not be measuring the same antibody. The single radial haemolysis test can distinguish between dengue and Japanese encephalitis viruses using specific mouse hyperimmune sera. Tests on a limited number of sera from Japanese encephalitis patients also showed no cross-reactions with dengue virus antigens in those cases having a low-titred but significant fourfold antibody rise to Japanese encephalitis antigen.

Dengue↗
PubMed1983

Amikacin in the treatment of pulmonary tuberculosis.

Sensitivity tests on strains from 11 patients with pulmonary tuberculosis, previously treated with kanamycin and/or capreomycin, showed incomplete cross-resistance between amikacin and capreomycin but complete cross-resistance between amikacin and kanamycin. Treatment with amikacin of 4 patients with multiply resistant strains resulted in no response as assessed by sputum smears and cultures, but resistance emerged to amikacin, kanamycin and capreomycin. Amikacin has no role in the treatment of tuberculosis as it cannot be given as an alternative to kanamycin, has no advantages over it and is more expensive.

Adult↗
PubMed1972

Immunoglobulin levels in newborn infants with hepatosplenomegaly.

Serum IgM and IgA levels were measured in 97 newborn infants with and 141 without hepatosplenomegaly. All were considered normal at birth and had no apparent disease on clinical examination. Thirty per cent. of the infants with hepatosplenomegaly were found to have IgM levels of 20 mg/100 ml or greater, a level established as abnormal when compared with the control group. The number of infants with raised IgM level and the geometric mean level were significantly different (P < 0.001) from those in the control group. No difference, however, was found in serum IgA levels between the two groups of infants. The results suggest that intrauterine infections may sometimes be the cause of hepatosplenomegaly in newborn infants without apparent disease.

Female↗
PubMed1971

Aedes aegypti (L.) and Aedes albopictus (Skuse) in Singapore City. 1. Distribution and density.

The distribution and density of Ae. aegypti and Ae. albopictus in Singapore were assessed from extensive larval surveys carried out from 1966 to 1968 to evaluate their respective roles in the epidemiology of dengue haemorrhagic fever and to study their ecology in the urban areas. Ten urban areas where the majority of dengue haemorrhagic fever cases occurred were surveyed.The results showed that both species were common in the city, with Ae. aegypti being the dominant species. The distribution of Ae. aegypti was more uniform and related to the prevailing housing types and conditions. Its premise index was highest in slum houses, intermediate in shop houses, and lowest in multistorey flats. Ae. albopictus, on the other hand, did not seem to be related to the prevailing housing type in its distribution but tended to be more widespread in areas with open spaces.The larval density index (the average number of larvae per housing unit) was higher for Ae. aegypti than for Ae. albopictus, in agreement with the relative densities shown by their premise indices. The larval density index correlated well with the premise index and correlated best with the infested-receptacle index. For practical purposes, the most suitable, convenient, and reliable measure of density of Ae. aegypti population seems to be the infested-receptacle index.An attempt was made to estimate the rate of dispersal of Ae. aegypti from a stable population to an adjacent area of multistorey flats. The rate of dispersal, estimated from the premise index and the larval density index, was approximately 2% per year of the "donor" population.

Aedes↗
PubMed1971

Aedes aegypti (L.) and Aedes albopictus (Skuse) in Singapore City. 2. Larval habitats.

Detailed information on the breeding habitats of Ae. aegypti and Ae. albopictus is necessary when planning programmes for their control. The larval habitats of the two species in 10 city areas were counted and classified according to type, frequency of occurrence, location, and function. Of all the breeding habitats recorded 95% were domestic containers. The most common Ae. aegypti breeding habitats were ant traps, earthenware jars, bowls, tanks, tin cans, and drums, ant traps being the most common indoors and earthenware jars the most common out doors. Breeding habitats for Ae. albopictus were commonly found in earthen ware jars, tin cans, ant traps, rubber tires, bowls, and drums; ant traps were the most common indoor habitat and tin cans were most common outdoors.The majority of Ae. aegypti breeding habitats were found indoors, while only half of all the Ae. albopictus breeding habitats were indoors. The indoor and outdoor distribution of breeding habitats of both species was not related to the type of housing in the area.The distribution of the type of breeding habitats, however, was related to the type of housing in the area. Ant traps were common to all areas, but water-storage containers and unused containers were common in slum-house and shop-house areas. Flats, however, had more containers used for keeping plants and flowers.The most common breeding habitats of Ae. aegypti and Ae. albopictus are discussed in relation to the habits of the people. It is concluded that control of the two species will depend largely on a change in such habits, either through public health education or by some form of law enforcement.

Aedes↗
PubMed1971

Aedes aegypti (L.) and Aedes albopictus (Skuse) in Singapore City. 3. Population fluctuations.

Fluctuations in the adult Ae. aegypti and Ae. albopictus populations and their relationship to rainfall were studied by weekly collections from a number of stations in the city. Aedes aegypti populations generally fluctuated with the rainfall, with multiple peaks, except in the middle of the year when there was no increase in rainfall at the time of the peak in population. It is suggested that other regulating factors, in addition to rainfall, also determine the fluctuations of this species. Aedes albopictus also fluctuated, with three peaks in a year, and these bore a close relationship to rainfall.In one area, both larvae and adults of Ae. albopictus were studied simultaneously. The larval populations were investigated by exposing tin cans in the field. The population peaks of larvae were found to precede those of adults by almost exactly 2 months. It is suggested that each adult population peak represents the cumulative effect of more than one generation of mosquitos.

Aedes↗
PubMed1971

Aedes aegypti (L.) and Aedes albopictus (Skuse) in Singapore City. 4. Competition between species.

There is a current belief stemming from statements made in the literature that Ae. aegypti is displacing Ae. albopictus in a number of cities of South-East Asia and in Calcutta, India. A critical review of these works showed that either the observations were inconclusive or the methods of collection were biased for one or the other species.Extensive surveys of the larval habitats of the two species in Singapore showed that the sharing of breeding habitats was uncommon in both urban and rural areas. In the laboratory, Ae. aegypti took a slightly shorter time to complete its development from egg-hatching to adult emergence.It is concluded that information available at present is insufficient to interpret the Ae. aegypti-Ae. albopictus population balance resulting from interspecific competition in Singapore. The pattern of distribution of the two species is unlikely to be the result of competitive displacement; it is, rather, probable that this pattern results from factors that favour the rapid increase and spread of one species over the other. It is suggested that Ae. aegypti in the city is favoured by rapid and extensive urbanization and by the higher fecundity and shorter life cycle of the species.

Aedes↗
PubMed1971

Aedes aegypti (L.) and Aedes albopictus (Skuse) in Singapore City. 5. Observations in relation to dengue haemorrhagic fever.

Dengue haemorrhagic fever in Singapore was a disease of the urban human population, with concentrations of cases occurring in areas of high population density. Mosquito surveys revealed that these areas also had high population densities of Ae. aegypti and Ae. albopictus.The disease occurred throughout the year but the incidence of cases appeared to follow a seasonal pattern. Observations from 1966 to 1968 showed that the number of cases increased in April, reached a peak in November, and, thereafter, decreased until the next increase in April of the following year. The epidemic curve generally agreed with the fluctuations of both Ae. aegypti and Ae. albopictus populations, although the latter species appeared to show a better correspondence with the incidence of cases.Six dengue viruses were isolated from the two Aedes species during 1966. One dengue type 2 virus was isolated from a pool of Ae. aegypti and 1 dengue type 1 virus and 4 dengue type 2 viruses were recovered from 5 pools of Ae. albopictus. These viruses were isolated from mosquitos collected during the period of increase in the incidence of cases and in 4 different areas of the city. The dengue virus infection rates per 1 000 mosquitos estimated in the present study were 0.51 for Ae. aegypti and 0.59 for Ae. albopictus.The data obtained in the present study suggest that both Ae. aegypti and Ae. albopictus are involved in the transmission of dengue haemorrhagic fever in Singapore.

Aedes↗