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Biomedical subjects

K T Goh

Publications and source records attributed to K T Goh.

At least 55 records · Page 3Linked to original sources
PubMed1993

Seroepidemiology of hepatitis A and hepatitis B virus infection in a Gurkha community in Singapore.

The overall prevalence of hepatitis A virus (HAV) infection among the Gurkhas and their families stationed in Singapore was 83.2%, with antibody to HAV detected in 67 (38.1%) of 176 children under 5 years of age, 121 (76.6%) of 158 children between 5 and 14 years, and 600 (97.9%) of 613 older children and adults over age 15 years. Children born in Singapore (102/223 or 45.7%) had a significantly lower crude prevalence than those born in Nepal (85/110 or 77.3%) (P < 0.000001). The age-adjusted difference in prevalence was also statistically significant (P < 0.001). Susceptible children had a high risk of acquiring HAV infection when they travelled to Nepal. As for hepatitis B virus (HBV) infection, the prevalence of hepatitis B surface antigen (HBsAg) was 2.8%, with a higher rate in males (20/560 or 3.6%) than in females (6/384 or 1.6%). The highest HBsAg prevalence (4/26 or 15.4%) was in young adult Gurkhas 15-19 years of age. No significant difference in the crude prevalence of HBV markers was noted between children born in Singapore (45/224 or 20.1%) and those born in Nepal (19/107 or 17.8%). Even after age adjustment, the difference remained insignificant. The prevalence of HBV markers of children of seropositive parents (27/156 or 17.3%) was not significantly higher than that of seronegative parents (19/131 or 14.5%). Married men had a significantly higher age-adjusted prevalence of infection than unmarried men (45.4% and 32.4%, respectively; P < 0.05). Seropositivity of one spouse was significantly correlated with the seropositivity of the other (P < 0.05), suggesting a role for heterosexual transmission of HBV infection.

Adolescent↗
PubMed1993

Epidemiology of typhoid fever in Singapore.

A total of 1452 cases of typhoid fever was notified in Singapore from 1980-9. The morbidity rates of indigenous cases showed a steady decline from 5.9 per 100,000 population in 1980 to 1.2 per 100,000 population in 1989. The mean case fatality was 0.8%. Children, adolescents and young adults were most susceptible to typhoid fever. There was no significant difference in morbidity rates between the major ethnic groups. The vast majority of indigenous cases were sporadic while outbreaks accounted for almost one third of them. Food was the main vehicle of transmission. The commonest indigenous phage types were B1, D1 and A. Antimicrobial resistance was infrequently seen. The proportion of imported cases rose from 32% in 1980 to 72% in 1989. Almost half (48.5%) of all imported cases were local residents who contracted typhoid fever while travelling in endemic countries. As imported cases assume greater importance in the epidemiology of typhoid fever in Singapore, further drop in typhoid fever incidence would require reduction of travel-related cases through greater awareness of food hygiene and effective vaccination.

Adolescent↗
PubMed1993

Epidemiology of sudden unexpected death syndrome among Thai migrant workers in Singapore.

A total of 235 cases of sudden unexpected death syndrome (SUDS) among apparently healthy male Thai migrant workers in Singapore were reported between 1982 and 1990. Most of the deaths occurred during sleep and 13% were not sleep-related. The median age at the time of death was 33 years and the median interval between arrival and death was 8 months. These deaths occurred singly and sporadically throughout the year. Post-mortem examination revealed few abnormal findings except for haemorrhagic congestion or oedema of the lungs. There were moderate to severe intra-alveolar haemorrhages with some evidence of myocarditis or pneumonitis. Preliminary findings of serial sections of the hearts indicate evidence of anomalies in the cardiac conduction system. Epidemiological investigations showed that a family history of similar deaths and serological evidence of current or recent infection with Pseudomonas pseudomallei were significantly associated with SUDS. Extensive biochemical and toxicological investigations were inconclusive. There was no evidence of chronic deficiency in thiamine or potassium among the healthy Thai workers living and working in the same conditions as the cases, and no significant abnormalities were detected on electrocardiographic examination. As these migrant workers experienced various psychosocial problems which could stem from maladjustment to an urban environment, separation from the family, burden of debts and long hours of work, stress could be a precipitating factor for SUDS.

Adult↗
PubMed1992

Epidemiology and control of an outbreak of typhoid in a psychiatric institution.

An outbreak of typhoid caused by Salmonella typhi of the same Vi-phage type (D1) and of the same antibiogram was reported in a large psychiatric institution in Singapore. A total of 95 (4.8%) of the 1965 inmates were infected, 47 with symptoms and 48 asymptomatic. Transmission was through close person-to-person contact and not through contaminated food or water. The source of infection could not be established. The outbreak was brought under control by maintaining a high standard of environmental sanitation, active search for fever and diarrhoeal cases, identification of asymptomatic cases by rectal swabbing, and isolation of those found to be infected. Mass immunization with two doses of heat-phenol inactivated typhoid vaccine was also carried out concurrently. The vaccine was found to have an efficacy of 65.8% in preventing clinical illness.

Adult↗
PubMed1992

Prevalence of varicella-zoster virus infection in Singapore.

The incidence of chickenpox in Singapore has been increasing since 1984. A seroepidemiological survey was conducted in 1989-90 to determine the prevalence of varicella-zoster virus-specific IgG antibody in the healthy population in Singapore aged from 6 months to over 45 years. Overall, 42.8% of 500 samples assayed qualitatively by the ELISA method were positive, with less than one fifth of those aged under 15 years and less than half of the 15-24 year olds possessing antibody to the virus. However, antibody prevalence increased markedly to between 86% and 98% in those over 25 years of age. No significant sex or ethnic difference was noted. The survey confirmed the low herd immunity and the higher susceptibility of the young adult population to varicella infection in a tropical city compared to that of temperate countries.

Adolescent↗
PubMed1992

Comparison of the immune response of four different dosages of a yeast-recombinant hepatitis B vaccine in Singapore children: a four-year follow-up study.

The immunogenicity of four different dosages of yeast-derived hepatitis B vaccine (Merck, Sharp & Dohme: 0.6 micrograms, 1.25 micrograms, 2.5 micrograms and 5.0 micrograms), administered at 0, 1 and 6 months (0-1-6 schedule) intramuscularly, was evaluated in 122 seronegative healthy children 1-12 years of age. Three months after the first dose, 83.9-100% of the vaccinees seroconverted. Peak geometric mean titres (GMT) of between 1088 mlU/ml and 1699 mlU/ml were attained 3 months after completion of the vaccination schedule. After 24 months, anti-HBs (antibody to hepatitis B surface antigen) was detected in 93.1-100% of the vaccinees, but the GMT dropped to between 214.3 mlU/ml and 303.5 mlU/ml. After 48 months, 88.8-100% of the vaccinees continued to possess anti-HBs and 70.3-87% had titres above 10 mlU/ml. As expected, the GMT declined further to between 72.6 mlU/ml and 118.8 mlU/ml. There were no significant differences in seroconversion rates and GMT among the different dosage groups. All the vaccinees remained asymptomatic and free from hepatitis B virus infection. The study showed that reduced dosages of the vaccine (0.6 micrograms, 1.25 micrograms and 2.5 micrograms) were as immunogenic as the standard dose (5 micrograms); the 2.5-micrograms dose was recommended for the national childhood immunization programme in Singapore. No booster is necessary for at least four years after vaccination.

Antibody Formation↗
PubMed1991

Sudden unexplained death syndrome--a new manifestation in melioidosis?

The indirect haemagglutination (IHA) test using sensitized turkey erythrocytes and the indirect immunofluorescence assay (IgM-IFA) was confirmed to be sensitive in the detection of a recent or current Pseudomonas pseudomallei infection in 19 culture-confirmed Singapore melioidosis patients. All were found to have antibody titres from 4 to 32768 in the IHA test and 10 to 320 in the IgM-IFA test. When these tests were employed on sera from 16 immigrant Thai construction workers who died of sudden unexplained death syndrome (SUDS) and 73 healthy Thai fellow workers, 93.8% and 68.8% of SUDS cases had IHA titre of greater than or equal to 4 and IgM-IFA titre of greater than or equal to 10 respectively, in contrast to 39.7% and 12.3% found among healthy Thai workers. These data indicate that at the time of death, most of the SUDS patients had an active infection with P. pseudomallei, possibly resulting from reactivation of a latent infection. The aetiological role of P. pseudomallei as the major cause of SUDS is discussed.

Adult↗
PubMed1991

Tussockosis: an outbreak of dermatitis caused by tussock moths in Singapore.

An outbreak of acute pruritic rash occurred in March 1990 among 141 residents of a high-rise public housing estate in Bukit Panjang, Singapore. The typical rash consisted of urticarial lesions distributed over the limbs and trunk. The outbreak was associated with a transient increase in tussock moths in the residential estate following an unusual, short dry spell. The aetiology was established when patch tests with crude moth material produced similar eruptions in 5 out of 7 adult volunteers between 40 min and 12 h. Pharmacological experiments with an aqueous extract of moth hairs in isolated guinea pig ileum elicited a response similar to that induced by histamine.

Adolescent↗
PubMed1991

Tussock moth dermatitis: evidence for histamine involvement.

Moth hairs shed by the few tussock moths caught during the first documented outbreak of pruritic dermatitis in Singapore were investigated to provide evidence for the presence of histamine. Aqueous extract of the moth hairs was used for the test and analyses. In the isolated guinea pig ileum, the extract, like histamine, produced responses that were blocked by mepyramine. The high performance liquid chromatographic (HPLC) analysis of the fluorescamine derivative of the moth extract resulted in a fluorescent peak with exactly the same retention. time as the histamine fluorescamine derivative. The mass spectrum of the pentafluoropropionic acid (PFP) derivative of the extract was also identical to that obtained from the reference histamine-PFP derivative. We concluded that histamine was present in the tussock moth hairs and was involved as one of the inflammatory mediators responsible for the pruritic skin rashes.

Animals↗
PubMed1991

Clearance of neonatal antiHBc following hepatitis B vaccination: relationship to antiHBs levels.

The persistence of antiHBc following hepatitis B virus (HBV) infection is sometimes regarded as evidence of a past infection, and the antiHBc inhibition of T-cell cytotoxic killing of HBV may be one way of tolerance leading to the carrier state. A model for studying the possibility of an immune tolerance occurring in the human situation was to observe the natural clearance rate of total antiHBc in babies who have acquired naturally maternal transferred antibodies, and to compare antiHBcIgG clearance and development of hepatitis B surface antigenaemia with the level of antibody to HBsAg (antiHBs), which is normally known to be virucidal. Two hundred and ninety-one normal infants who received hepatitis B vaccination in 1984 were followed and studied at six months, one, two and four years. AntiHBc was not found in any control infants born of HBsAg negative mothers. One child became antiHBc positive at four years reflecting acquired infection when antiHBs level had fallen to 36 mIU per ml. AntiHBc cleared in 66% of HBsAg pos./'e' neg. children at one year and completely by two years. In contrast, antiHBc clearance in children born of HBsAg pos./'e' pos. was inversely related to the antiHBs levels. Those with antiHBs levels over 50 mIU per ml cleared antiHBc more rapidly and were HBsAg negative, whereas in 28/49 (57%) HBs antigenaemia were associated more often with antiHBs under 10 mIU per ml and in 2/43 (5%) at levels between 11 to 50 mIU per ml. Two children who had later developed HBs antigenaemia in the presence of antiHBs after responding to earlier passive-active immunisation, suggest either defective antiHBs and/or the development of mutants or variants.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies, Anti-Idiotypic↗
PubMed1991

Typhoid fever in Singapore: a review of 370 cases.

The medical records of 370 patients treated for typhoid fever between 1986 and 1988 at the Communicable Disease Centre, Singapore, were reviewed. The disease was generally mild. There was no mortality. Fever was found in 98.4% of patients on admission and diarrhoea in 21%. Cough was predominantly a symptom of children and occurred in 7.1% of patients aged below 15 years. Other symptoms were uncommon. Hepatomegaly was found in 71% and splenomegaly in 47%. Leucopenia was not a helpful diagnostic marker. Chloramphenicol was the drug of choice. The relapse rate was 5.4% and the convalescent and temporary carrier rates 11.6%. The risk of developing the carrier state was significantly higher among patients who were afebrile on admission compared with those who were febrile (P less than 0.001); it was also higher in patients treated with ampicillin as compared to those treated with chloramphenicol (P less than 0.001, chi 2 = 22.7, odds ratio = 5.25, 95% confidence limits: 2.46 and 11.29). The role of ampicillin as a first line treatment for acute typhoid fever may need further re-evaluation.

Adolescent↗
PubMed1990

Acute haemorrhagic conjunctivitis: seroepidemiology of coxsackievirus A24 variant and enterovirus 70 in Singapore.

Epidemics of acute haemorrhagic conjunctivitis caused by a variant of coxsackievirus A24 (CA24v) and enterovirus 70 (EV70) have occurred periodically in Singapore. A seroepidemiological survey conducted before the CA24v epidemic in 1985 and in the midst of the EV70 epidemic in 1983 showed a neutralising antibody prevalence (greater than or equal to 1:4) of 19.1% and 66.9% to CA24v and EV70, respectively. The seropositivity rate to both viruses was highest in children 10-14 years of age, but no sex or ethnic difference was noted. It appears from the data that an epidemic could be triggered when the herd immunity of the population falls below a critical level. There was a significant correlation in seroprevalence between CA24v and EV70 (P = 7.75 x 10(-3).

Adolescent↗
PubMed1990

Person-to-person transmission of cholera in a psychiatric hospital.

An outbreak of cholera caused by Vibrio cholerae O1, biotype el tor, serotype Ogawa, phage type 4, was reported in a psychiatric hospital in Singapore. A total of 74 inmates (18 symptomatic and 56 asymptomatic) were infected; two of them died. Extensive epidemiological investigations showed that the organism was not transmitted by contaminated food or water but through close person-to-person contact. Early recognition of the outbreak and prompt implementation of epidemic control measures comprising surveillance of diarrhoea, rectal swabbing of all asymptomatic inmates, isolation of those found to be infected, maintenance of a high standard of environmental sanitation and mass chemoprophylaxis with doxycycline, rapidly brought the outbreak under control.

Adult↗
PubMed1989

The hepatitis B immunization programme in Singapore.

A voluntary immunization programme to prevent perinatal transmission of hepatitis B virus (HBV) infection in Singapore was implemented on 1 October 1985 as an integral component of the national childhood immunization programme. Up to April 1988, a total of 68,845 mothers who attended government maternal and child health clinics were screened for the disease. Of these, 2432 (3.5%) were positive for hepatitis B surface antigen (HBsAg) and 904 (1.3%) for hepatitis B e antigen (HBeAg). Virtually all the babies born to carrier mothers completed the full immunization schedule; and in addition, those of HBeAg-positive mothers were given a dose of hepatitis B immunoglobulin at birth. The hepatitis B immunization programme was extended on 1 September 1987 to cover all newborns. About 90% of the 15,943 babies delivered in government institutions from September 1987 to April 1988 were immunized at birth, with the subsequent doses being administered at maternal and child health clinics at 4-6 weeks and 5 months later. More than 85% of the children given the full course of plasma-derived and yeast-derived hepatitis B vaccine from birth continued to have protective antibody to HBV two years after immunization. The programme is being closely monitored to assess the duration of immunity and the need for booster doses, while seronegative adults are also being encouraged to be vaccinated.

Adolescent↗
PubMed1989

Legionella species, serogroups and subgroups found in the environment in Singapore.

Over a period of seven months, 87 samples of water collected from 48 air-conditioning cooling-towers on 15 sites in Singapore yielded 19 strains of Legionella. Legionellas were found in 7 of the 15 sites. The strains isolated fell into 7 species, serogroups or subgroups of the genus Legionella. Only 11% of them belonged to the more pathogenic Pontiac subgroup of Legionella pneumophila serogroup 1.

Disease Outbreaks↗
PubMed1988

The prevalence of hepatitis B virus markers in dental personnel in Singapore.

A seroepidemiological survey of the prevalence of hepatitis B virus (HBV) markers was conducted in a group of 693 dental personnel in Singapore where HBV infection is endemic. The overall prevalence of HBsAg (4.5%) and anti-HBc (29%) was no higher than that in the general population. However, dentists had a significantly higher HBsAg prevalence (11.4%) compared with that in the general population (4.2%) (P less than 0.01) and of other categories of dental personnel (3.1%) (P less than 0.001). Similarly, the anti-HBc prevalence of the dentists (45.6%) was significantly higher than that of the general population (29.7%) (P less than 0.01) and of other categories of dental personnel (25.7%) (P less than 0.0001). It appears that dentists in the endemic area have a definite occupational risk of acquiring HBV infection.

Dental Staff↗