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Biomedical subjects

K T Goh

Publications and source records attributed to K T Goh.

At least 37 records · Page 2Linked to original sources
PubMed1997

Surveillance of legionellosis and Legionella bacteria in the built environment in Singapore.

During the period 1986 to 1996, a total of 258 sporadic cases of community-acquired legionellosis was reported, giving a mean annual morbidity rate of 0.9 per 100,000 population. Majority of the cases (91.5%) was serologically diagnosed by the indirect fluorescent antibody (IFA) test against Legionella pneumophila based on single sera with a titre of > or = 1:1024. The others were confirmed by a four-fold increase in IFA titre to a minimum of 1:128 (7.4%) and by culture (1.1%). Cases were reported predominantly among males, ethnic Indians, the elderly and those with concurrent medical conditions. The overall case-fatality rate was 14.7%, with the rate significantly higher among those aged > or = 45 years (21%), smokers (20.4%) and those with concurrent medical conditions (22.5%). Seroepidemiological studies among the healthy population based on an IFA titre of > or = 1:32 showed a prevalence of between 10.3% and 21.9%. Of the various occupational groups investigated, high seroprevalence rates were found in foreign construction workers (52.6%) and occupants of a building investigated for an unusual building-related illness (76.1%). Environmental surveillance of Legionella bacteria showed that 36% of cooling towers, 15% to 19% of decorative fountains and waterfalls and 2% of spa pools were positive. The majority (85%) of environmental isolates was identified as Legionella pneumophila: 54.8% of serogroup 1 and 5% of Pontiac subtype.

Adolescent↗
PubMed1997

Local transmission of Plasmodium vivax malaria in Singapore.

A localised outbreak involving 19 cases and two carriers of vivax malaria was reported at Dairy Farm from May to June 1996. Epidemiological investigations showed that the outbreak was caused by the introduction of two foreign workers with imported relapsing vivax malaria into this malaria-receptive area. Transmission of infection occurred amongst 17 other foreign workers residing in the locality and two local residents staying at a condominium nearby. The outbreak was rapidly brought under control through active case finding, isolation and treatment of infected persons, epidemic vector control measures, and improved drainage to prevent Anopheles maculatus breeding. Were it not for the very thorough epidemiological investigations in this episode, foreign workers and local residents with a recent travel history would have been misclassified as imported and the outbreak missed. Medical practitioners should always consider the possibility of malaria in a foreign worker presenting with fever and notify the case as soon as the disease is suspected.

Animals↗
PubMed1997

Dengue--a re-emerging infectious disease in Singapore.

Despite its well-established integrated nationwide Aedes mosquito control programme which incorporates source reduction, public health education and law enforcement, Singapore has not been spared from the regional resurgence of dengue. The disease incidence has been increasing from 9.3 per 100,000 in 1988 to 102.7 per 100,000 in 1996 at the time when the Aedes house index (HI) has dropped to around 1% from > 25% in the 1960s. Majority of the cases reported from 1990 to 1996 were dengue fever (DF); dengue haemorrhagic fever (DHF) constituted only 6.7%. The case-fatality rate was 0.1% with 13 (81.3%) of 16 serologically confirmed deaths above 19 years of age. The median age has shifted from 14 years in 1973 to 27 years in 1996. The proportion of primary infections also increased from about one-third in 1990 to nearly half in 1996. All four dengue serotypes have been detected from infected persons with dengue 2 predominating in 1990, 1991 and 1993, dengue 3 in 1992 and 1994 and dengue 1 in 1995 and 1996. The disease incidence was significantly correlated with Aedes aegypti HI and residents of compound houses had a significantly higher rate of infection as well as a higher morbidity rate compared with dwellers of high-rise public housing estates. Seroprevalence surveys confirmed the low level of dengue transmission. The immunity level of the general population has been declining with only 6.4% of children and young adults below 25 years of age possessing haemagglutination-inhibition antibody to dengue 2. It would appear that the successful vector control programme over the last two decades has brought about a paradoxical situation in that outbreaks tend to occur more frequently and with even greater intensity because of the low herd immunity of the population. Until the dengue vaccine is commercially available for mass immunisation of the population, community-based integrated control of Aedes aegypti remains the key to the prevention and control of DF/DHF.

Adolescent↗
PubMed1997

Prevention and control of hepatitis B virus infection in Singapore.

Hepatitis B virus (HBV) accounted for 24% to 54% of the reported acute viral hepatitis cases in Singapore from 1982 to 1996. The prevalence of HBV infection, as indicated by the presence of markers of HBV, increased from 9.3% in children below 5 years of age to 54.6% in adults above 55 years. The overall hepatitis B surface antigen (HBsAg) prevalence was 5.7% for males and 3.4% for females, with the highest rate among the Chinese. About 39% of the HBsAg carriers were hepatitis B 'e' antigen positive. The main mode of transmission during the first year of life was perinatal, with 43% of the babies born to HBsAg-positive mothers developing the carrier state. Horizontal transmission within the infected household was significantly associated with sharing of personal and household articles. Based on the findings of seroprevalence surveys in various population groups and clinical trials on the safety, immunogenicity and efficacy of various doses and schedules with the plasma-based and yeast-derived hepatitis B vaccines in newborn babies, a national childhood hepatitis B vaccination programme was formulated and implemented in phases, starting with babies born to carrier mothers on 1 October 1985 and finally extending to all newborns on 1 September 1987. The hepatitis B prevention and control programme has been successful. During the period 1994 to 1996, more than 90% of children completed the full schedule of immunisation by below one year of age, and 85% had evidence of vaccination at school entry at age six. Follow-up of 2 cohorts of vaccinated children showed that perinatal transmission has been reduced by 80% to 100%. Horizontal transmission has also declined through other public health measures. The efficacy of the hepatitis B vaccine and the adequacy of reduced doses in the long-term protection of chronic carrier state have been shown in children and adults. The incidence of acute hepatitis B has declined from 10.4 per 100,000 in 1985 to 4.8 per 100,000 in 1996. There is a noticeable reduction in HBsAg prevalence in selected population (school children, national servicemen and antenatal women). The age-standardised incidence rate of primary liver cancer among males had also dropped from 27.8 per 100,000 per year during 1978 to 1982 to 19.0 per 100,000 per year during 1988 to 1992.

Age Factors↗
PubMed1995

Molecular epidemiology of hepatitis B virus vaccine variants in Singapore.

Perinatal infection with variants of hepatitis B virus occurs despite combined immunoprophylaxis with hepatitis B immunoglobulin and currently licensed plasma-derived and recombinant yeast hepatitis B vaccines. Several variants have been detected during a large study of infants born to carrier mothers in Singapore. The most frequent variant was a virus in which a single amino acid substitution Gly to Arg occurred at amino acid position 145 of the outer protein coat of the virus. Similar mutations have been described in Italy, Japan, the USA and a number of other countries. The emergence of antibody escape mutants is a cause for concern for the detection of virus and possibly for future immunization programmes.

Amino Acids↗
PubMed1995

Prevalence of hepatitis B virus (HBV) infection in Singapore men with sexually transmitted diseases and HIV infection: role of sexual transmission in a city state with intermediate HBV endemicity.

STUDY OBJECTIVES: To describe the prevalence of hepatitis B virus (HBV) infection in patients with sexually transmitted diseases (STD) and human immunodeficiency virus (HIV) infection, and to determine the role of sexual transmission of HBV infection in Singapore. DESIGN: A cross sectional study of all consecutive men presenting with a new episode of STD at a government outpatient clinic and all men with HIV infection on routine follow up at a government hospital. The prevalence of various HBV markers was compared with that of healthy males aged 15 years and above (controls). SETTING: Singapore, a city state of intermediate HBV endemicity. SUBJECTS: These comprised 497 STD patients, 47 HIV infected patients, and 418 controls. MAIN RESULTS: The overall seroprevalences of HBV infection in STD patients, HIV infected patients, and control subjects were 41.2%, 61.7%, and 33.3%, respectively (p < 0.001). The seroprevalences of hepatitis B surface antigen (6.2%, 8.5%, and 4.5%, respectively) were comparable in the three groups. Using stepwise logistic regression analysis, the adjusted seroprevalences of HBV infection in STD and HIV infected patients were respectively 2.4 times (95% confidence interval (CI), 1.7, 3.3) and 3.3 times (95% CI 1.7, 6.3) higher than in controls. HBV infection rates were higher among Chinese (odds ratio (OR), 1.9; 95% CI 1.6, 3.4) than non-Chinese, and among those aged 25-34 years (OR 2.4; 95% CI 1.6, 3.4), 35-44 years (OR 3.9; 95% CI 2.5, 5.9), and 45+ years (OR 6.2; 95% CI 3.8, 10.2) than in those aged 15-24 years. Sex related factors significantly associated with higher infection rates, independent of age and ethnic group, were reactive VDRL test (OR 2.4; 95% CI 1.2, 4.7), participation in anal intercourse (OR 2.3; 95% CI 1.2, 4.3), and having 10 or more lifetime sexual partners (OR 1.5; 95% CI, 1.0, 2.1). CONCLUSION: The importance of sexual transmission of HBV in an area of intermediate HBV endemicity was confirmed. Patients attending STD clinics should be routinely screened for HBV markers and those found to be seronegative should be strongly advised to be immunised against this virus.

Adolescent↗
PubMed1995

Long-term immunogenicity and efficacy of a reduced dose of plasma-based hepatitis B vaccine in young adults.

A cohort of seronegative preclinical medical and dental students and another cohort of seronegative national service recruits who were immunized intramuscularly with a reduced dose (10 micrograms) of plasma-based hepatitis B vaccine (Merck, Sharp & Dohme) at the start of the study and at 1 month and 6 months thereafter were followed up for 5 years and 6 years, respectively. Among the medical and dental students, antibody to hepatitis B surface antigen (anti-HBs) ( > or = 10 mlU/ml) was detected in 81% of the vaccinees at the end of the 5-year follow-up and the geometric mean titre (GMT) had dropped from 412.6 mlU/ml one year after completion of vaccination to 174.9 mlU/ml after 5 years. Antibody to hepatitis B core antigen (anti-HBc) was detected in 0.4-1.0% of the vaccinees but none was positive for hepatitis B surface antigen (HBsAg) during the follow-up period. Among the national servicemen, the anti-HBs seroconversion rate and GMT were considerably lower than those of the preclinical medical and dental students. At the end of the 6-year follow-up, 55% of the vaccinees were positive for anti-HBs ( > or = 10 mlU/ml) and the GMT had dropped from 80.7 mlU/ml one year after completion of vaccination to 30.4 mlU/ml after 6 years. Anti-HBc was detected in 8 (2.7%) and transient HBs antigenaemia in 2 (0.7%) of 293 vaccinees after 4 years.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Immunogenicity of recombinant yeast-derived hepatitis B vaccine in nonresponders to perinatal immunization.

OBJECTIVE: Nonresponse to hepatitis B vaccine in the perinatal period occasionally occurs. This report documents the results of reimmunization of nonresponders to perinatal immunization. DESIGN: From a cohort of 1154 infants immunized with plasma-based vaccine in the perinatal period and followed up for more than 8 years, 45 nonresponders were identified. These children were reimmunized at 4 years of age. Each child received a yeast-derived recombinant hepatitis B vaccine on a 0-, 1-, and 5-month schedule, 33 children with 10-micrograms and 12 with 5-micrograms doses. Blood was sampled 1 month after the third vaccination and thereafter at 1, 2, and 4 years. SETTING: The follow-up clinic where the cohort of children was regularly seen. PATIENTS: Forty-five 4-year-old children who had no antibody to hepatitis B despite perinatal immunization. MAIN OUTCOME MEASURE: Antibody levels to hepatitis B surface antigen. RESULTS: Seroconversion with titers higher than 10 mIU/mL occurred in all children. More than 70% still had titers higher than 10 mIU/mL 4 years after vaccination. CONCLUSION: Nonresponders to perinatal hepatitis B vaccination respond well to subsequent vaccination.

Child↗
PubMed1994

Prevalence of hepatitis A virus infection among sewage workers in Singapore.

To determine whether or not occupational exposure to sewage is associated with a higher seroprevalence of hepatitis A virus (HAV) infection, 600 sewage workers in Singapore were tested for total (IgG and IgM) antibody to HAV by enzyme immunoassay. Using logistic regression with stepwise procedure, the adjusted seroprevalence of sewage workers was 2.2 times higher than that of another non-occupationally exposed population group. Seroprevalence was significantly correlated with age and educational levels, the association being independent of the occupational association. The epidemiological data in the study show that sewage workers have an increased occupational risk of acquiring HAV infection and should be protected by active immunization.

Adult↗
PubMed1994

Genome fingerprinting of Salmonella typhi by pulsed-field gel electrophoresis for subtyping common phage types.

The genomic DNA of 39 strains of Salmonella typhi isolated from local residents and patients who had visited countries in the Asian region was analysed for restriction fragment length polymorphisms (RFLP). Pulsed-field gel electrophoretic (PFGE) analysis of Xba I- and Spe I-generated genomic restriction fragments established 22 PFGE types whereas phage typing differentiated the 39 isolates into 9 distinct phage types. This study showed that PFGE is more discriminatory than phage typing as it is capable of subtyping S. typhi strains of the same phage types. Genetic relatedness among the isolates was determined. Seven major clusters were identified at SABs of > 0.80 and the remaining 13 isolates were distributed into minor clusters which were related at SABs of less than 0.80. In conclusion, PFGE analysis in conjunction with distance matrix analysis served as a useful tool for delineating common S. typhi phage types of diverse origins from different geographical locales and separated in time.

Adolescent↗
PubMed1994

Low prevalence of antibody to human parvovirus B19 in Singapore.

A seroepidemiological survey was conducted in Singapore to assess the prevalence of antibody to human parvovirus B19. Sera were collected from 600 healthy individuals between 6 months and over 50 years of age and tested for IgG antibody against B19 virus by antigen capture indirect immunosorbent assay. The overall seropositivity rate was 16.2%. All the children under 5 years of age were seronegative. Antibody prevalence increased gradually from 3.5% in school children (5-14 years of age) to 7.7% in age group 15-19 years and then to 10.3% in young adults (20-24 years of age). In the age group 25-34 years the prevalence was 28% and in the age group over 35 years 65% had parvovirus B19 antibody. The results of the survey indicate that there has been very low incidence of B19 virus infection in Singapore during the last two decades.

Adolescent↗
PubMed1994

Epidemiological investigations into an outbreak of building-associated illness in Singapore.

In August 1991, the Ministry of the Environment was informed of the occurrence of illnesses suspected to be related to a modern, multi-story office building. Investigations revealed that 34 of the occupants on two floors of the building had non-specific ailments such as eye, throat or skin irritation which caused acute discomfort but resolved upon leaving the premises. Case-control study identified a number of factors significantly associated with the illness; viz. a personal history of allergy, asthma or sinusitis; a high level of work-related stress; and a lack of thermal comfort. One feature of the affected offices was numerous high partitions which tended to obstruct air movement. Adjustments of central temperature to compensate for complaints of "stuffiness" had resulted in wide fluctuations of temperature and relative humidity. Indoor air quality measurements also revealed high bacterial counts, a condition aggravated by the raised relative humidity and inadequate air movement. The problems gradually resolved following major modifications at the offices and air-handling units. This episode confirmed the need for further studies of building-associated illness in the tropics.

Adult↗
PubMed1994

Vibrio cholerae 0139 'Bengal' in Singapore.

Vibrio cholerae 0139 was isolated from five patients with cholera-like illness. All were imported cases. Laboratory investigations found our five isolates in show similar morphological, biochemical and serological characteristics to the V. cholerae 0139 strains causing epidemics in Bangladesh and India. Our isolates were toxin producers resistant to streptomycin and co-trimoxazole. No local transmission was known to have occurred following introduction of these imported cases.

Adult↗
PubMed1993

A recent epidemic of acute hemorrhagic conjunctivitis.

The coxsackievirus A24 variant was implicated in four of six major acute hemorrhagic conjunctivitis outbreaks in Singapore since its discovery in 1970. Hela cell suspension in 24-well flat-bottom tissue culture plates was a satisfactory alternative to monolayer cells grown in test tubes for virus isolation. Respiratory illness occurred in 20 of 98 patients with acute hemorrhagic conjunctivitis. Apart from conjunctival secretions, respiratory and oral transmission of coxsackievirus A24 variant would explain the rapid and extensive spread of acute hemorrhagic conjunctivitis during an outbreak.

Adolescent↗