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Biomedical subjects

Y S Leo

Publications and source records attributed to Y S Leo.

At least 19 recordsLinked to original sources
PubMed2006

Influenza and the pandemic threat.

With the increasing concern of an imminent influenza pandemic, Singapore and many other countries have been developing preparedness plans. Influenza affects an estimated 20 percent of the population of Singapore annually, and local outbreaks can last for more than 12 weeks and occur at different periods of the year. The 1968 pandemic in Singapore had a clinical attack rate of about 20 percent and resulted in infections with fever that lasted up to five days. However, absenteeism from work due to seasonal influenza-like illnesses was estimated to be less than one day per person in Singapore. The next pandemic in Singapore is predicted to cause an average of 1,105 deaths and 3,338 hospitalisations, while a severe pandemic will cause more healthcare damage. Preventive strategies include national public health initiatives, vaccination, anti-viral therapy, and hygiene measures. To develop effective preparedness plans, it is important for healthcare workers to understand the disease's epidemiology, outcomes, and treatment and prevention strategies available.

Antiviral Agents↗
PubMed2005

Measurable predictive factors for progression to AIDS among HIV-infected patients in Singapore.

INTRODUCTION: This study identifies measurable factors at the time of diagnosis that predict the progression to Acquired Immunodeficiency Syndrome (AIDS) among Human Immunodeficiency Virus (HIV)-infected patients in Singapore. MATERIALS AND METHODS: We carried out a retrospective study of 790 HIV-infected patients from 16 May 1985 to 31 December 2001. The end-point was the onset of AIDS-defining illness listed in the 1987 and 1991 revised Centers for Disease Control and Prevention criteria, but excluded CD4 cell counts as a criterion. Using the Kaplan-Meier method, AIDS-free survival curves were plotted for age groups at diagnosis, baseline CD4 counts and periods for utilisation of antiretroviral treatment. A Cox regression model was constructed to determine independent predictors of disease progression. RESULTS: Univariate analysis showed that patients of older age at diagnosis had a significantly higher risk of progression compared to younger patients, and patients with higher baseline CD4 cell counts had a lower risk of progression to AIDS. Adjusting for the simultaneous influence of several covariates on the rate of HIV progression to AIDS, multivariate analysis using the Cox model showed a significantly higher risk of progression for older patients at diagnosis, and the progressive lowering of risk with increasing baseline CD4 cell counts. CONCLUSIONS: This study found older age at diagnosis and baseline CD4 cell counts to be measurable predictors for HIV progression to AIDS at time of diagnosis. Identification of these risk factors enables physicians to provide counselling and advice, and to start appropriate treatment early. This could lower the risk of progression and improve survival.

Acquired Immunodeficiency Syndrome↗
PubMed2005

Surveillance of severe acute respiratory syndrome (SARS) in the post-outbreak period.

INTRODUCTION: This retrospective one-month survey evaluated the practicality of post-severe acute respiratory syndrome (SARS) surveillance recommendations in previously SARS-affected countries, namely Singapore. These included staff medical sick leave for febrile illness, inpatient fevers, inpatient pneumonia, atypical pneumonia, febrile illnesses with significant travel history and sudden unexplained deaths from pneumonia/ adult respiratory distress syndrome (ARDS). METHODS: Surveillance data on medical sick leave of staff, all inpatient fevers, all febrile (temperature greater than or equal to 38 degrees Celsius) inpatient pneumonia, including atypical pneumonia, and deaths from pneumonia were collected from sick leave reports, ward reports, isolation room rounds and mortuary reports from 1 to 28 September 2003. RESULTS: Baseline results show 167 (1.4/1000 staff-days) observed in staff sick leave for febrile illnesses, and 1798 (71.3/1000 bed-days) observed for inpatient fever. There were 40, 31 and 12 instances, respectively, of staff having temperatures of high fever (greater than or equal to 38 degrees Celsius), prolonged sick leave (3 days or more), and repeated sick leave (within 7 days) for febrile illnesses. An average of 4.6 wards a day potentially fulfilled the World Health Organisation SARS alert criteria. Of 27 cases with fever, pneumonia and a total white count of less than 10,000 cells per cubic mm as per Ministry of Health, Singapore criteria for the diagnosis of atypical pneumonia, only five were identified by clinicians. CONCLUSION: Surveillance is time-consuming and current recommendations are not specific enough to be used practically. Surveillance indicators for inpatients must overcome a high degree of background noise.

Allied Health Personnel↗
PubMed2004

Severe acute respiratory syndrome and pulmonary tuberculosis.

In Singapore, of 236 patients with probable severe acute respiratory syndrome (SARS), 2 were coinfected with tuberculosis, a phenomenon not previously reported. The patients' tuberculosis episodes only came to light after full recovery from SARS, when they presented with persistent respiratory symptoms and/or worsening chest radiography findings.

Adult↗
PubMed2004

Factors associated with transmission of severe acute respiratory syndrome among health-care workers in Singapore.

Between 1 and 22 March 2003, a nosocomial outbreak of Severe Acute Respiratory Syndrome (SARS) occurred at the Communicable Disease Centre in Tan Tock Seng Hospital, Singapore, the national treatment and isolation facility for patients with SARS. A case-control study with 36 cases and 50 controls was conducted of factors associated with the transmission of SARS within the hospital. In univariate analysis, contact with respiratory secretions elevated the odds ratio to 6.9 (95 % CI 1.4-34.6, P= 0.02). Protection was conferred by hand washing (OR 0.06, 95% CI 0.007-0.5, P=0.03) and wearing of N95 masks (OR 0.1, 95% CI 0.03-0.4, P=0.001). Use of gloves and gowns had no effect. Multivariate analysis confirmed the strong role of contact with respiratory secretions (adjusted OR 21.8, 95 % CI 1.7 274.8, P=0.017). Both hand washing (adjusted OR 0.07, 95 % CI 0.008-0.66, P=0.02) and wearing of N95 masks (adjusted OR 0.1, 95% CI 0.02-0.86, P=0.04) remained strongly protective but gowns and gloves had no effect.

Adult↗
PubMed2003

Late clinical and magnetic resonance imaging follow up of Nipah virus infection.

The Nipah virus is a newly identified paramyxovirus responsible for an outbreak of fatal encephalitis in Malaysia and Singapore. This paper reports the follow up clinical and magnetic resonance imaging findings in 22 affected subjects. Of 13 patients with encephalitis, one died, one was lost to follow up, and seven recovered. Among the four remaining patients, one had residual sixth nerve palsy, another suffered from severe clinical depression, and a third patient had evidence of retinal artery occlusion. One patient with delayed onset Horner syndrome had a single lesion in the cervical spinal cord. The brain magnetic resonance findings were stable or improved in nine patients over 18 months of follow up. Among a second group of nine asymptomatic seropositive abattoir workers, magnetic resonance examination in seven subjects revealed discrete small lesions in the brain; similar to those detected in encephalitis patients. These findings suggest that in addition to encephalitis, the newly discovered Nipah virus affects the spinal cord and the retina. Late clinical and radiological findings can occur in Nipah virus infections as with other paramyxoviruses.

Abducens Nerve Diseases↗
PubMed2003

Chest radiographic findings of a case of severe acute respiratory syndrome (SARS) in Singapore.

A new form of atypical pneumonia was reported in the East Asian region beginning from early 2003. This was later termed by the World Health Organisation as Severe Acute Respiratory Syndrome (SARS). The diagnosis of SARS relies on a combination of clinical features and chest radiographic findings. A preliminary review of SARS in Singapore shows chest radiographic findings of patchy airspace shadowing with severe cases progressing to diffuse air-space shadowing. We illustrate these findings with temporal correlation in our case report. As SARS is a contagious, rapidly progressive and potentially fatal condition, early diagnosis is crucial for prompt management and isolation of patients. Recognition of chest radiographic findings aids in the early diagnosis and containment of SARS.

Adult↗
PubMed2002

A survey of Nipah virus infection among various risk groups in Singapore.

Following the Nipah virus (NV) outbreak in March 1999 in Singapore, a serological survey was undertaken to screen individuals potentially exposed to NV. Blood samples were tested for NV IgM, IgG and neutralizing antibodies. Twenty-two (1.5%) of 1469 people tested had antibodies suggesting NV infection. Although 12 of the 22 infected people (54.6%) were symptomatic, the remaining 10 (45.4%) were clinically well and had no past history of compatible pulmonary or neurological disease. Clinical and serological findings suggested three people had been infected with NV before the outbreak was recognized. All those who were infected were male abattoir workers. None of the people who had contact with horses, and no healthcare workers exposed to infected patients and their specimens had detectable antibodies. This study provides evidence that NV causes asymptomatic infection. All of the antibody positive individuals had direct contact with pigs and there was no evidence of human to human transmission.

Abattoirs↗
PubMed2001

Prevention of human immunodeficiency virus (HIV) transmission from mother to child--a cohort study in Singapore.

INTRODUCTION: The landmark Paediatric AIDS Clinical Trials Group (PACTG) trial 076 showed in 1994 that antiretroviral therapy (ART) was effective in reducing maternal-child transmission of human immunodeficiency virus (HIV). This trial included antenatal oral zidovudine (ZDV), intrapartum intravenous ZDV, 6 weeks of oral ZDV to the babies and no breastfeeding. MATERIALS AND METHODS: This study is an on-going, prospective, open-label trial conducted from 1995 in which we enrolled HIV-infected pregnant women using the above strategy. Since 1997, the antenatal component of the regimen was modified to include lamivudine with ZDV. All babies had serial HIV polymerase chain reaction (PCR) and antibody tests including enzyme-linked immunosorbent assay (EIA), particle agglutination (PA) and Western blot (WB) at day 1, 1 week, 1, 2, 3, 6, 12 and 18 months. RESULTS: A total of 16 out of 19 eligible women were recruited from 1995 to 1999. The median age was 26 years (range 22 to 38 years), 38% were Singaporeans, median CD4 was 421 cells/mL (range 18 to 713 cells/mL) and median baseline gestational age was 23.5 weeks (range 8 to 32 weeks). None of the 16 children was infected as evidenced by 2 negative HIV PCRs including 1 done > 4 months old with a follow-up of 6 months to 2 years. There was a statistically significant difference between the 3 HIV antibody tests at 12 months of age (P = 0.003), there being more negative results with WB as compared to PA (P = 0.02). However, the difference between the 3 tests at 18 months was not statistically significant. No long-term side effects in these children were seen. CONCLUSION: Although the number of patients in this study is small, the absolute prevention of transmission (95% confidence intervals 0%-17%) in this cohort supports the recommendation of antenatal HIV screening and treatment of those infected.

Adult↗
PubMed2001

Nucleoside analogue-induced fatal lactic acidosis in two HIV-infected patients in Singapore.

The introduction of antiretroviral therapy has led to a significant decrease in the mortality and morbidity associated with human immunodeficiency virus (HIV) infection. Nucleoside reverse transcriptase inhibitors (NRTI) have been widely used as part of the antiretroviral therapy against HIV. However, one recently recognised serious complication of NRTI is the development of lactic acidosis. We report two cases of fatal NRTI-induced lactic acidosis, which occurred within five months of each other. Both were being treated with didanosine (ddI) and stavudine (d4T). Physicians involved in the care of HIV patients should recognise and be alert to the possibility of this highly fatal complication.

Acidosis, Lactic↗
PubMed2001

Oral manifestations of human immunodeficiency virus (HIV)-infected patients in Singapore.

INTRODUCTION: Oral lesions have been recognised as prominent features of acquired immune deficiency syndrome (AIDS) and human immunodeficiency virus (HIV) infection since the beginning of the epidemic. OBJECTIVE: This descriptive study was conducted to study the types of oral lesions among HIV-infected patients in Singapore. MATERIALS AND METHODS: Oral examination was done on 81 randomly selected HIV-infected patients attending the specialist outpatient clinic at the Communicable Disease Centre. RESULTS: A total of 9 different lesions were observed in 45 (56%) patients. The lesions observed were oral candidosis (35%), periodontal disease (16%), aphthous-like ulcers (5%), oral hairy leukoplakia (5%) and lymphoma (1%). CONCLUSION: The oral manifestations of HIV-infected patients in Singapore appear to be less frequent in comparison with those patients from Africa and Europe. Similarities in oral findings among the HIV-infected patients in Asia are evident with a notable lack of oral Kaposi's sarcoma (KS) and a low prevalence of non-Hodgkin's lymphoma and oral hairy leukoplakia.

Adult↗
PubMed2001

Epidemiological, clinical and laboratory characteristics of 19 serologically confirmed rickettsial disease in Singapore.

AIM: To identify epidemiological, clinical and laboratory features of serologically-proven typhus in the local setting. METHOD & RESULTS: Retrospective study looking at rickettsial serologies done over a six-month period and collection of the epidemological, clinical, laboratory and treatment response data from the case notes of the patients with an ordered rickettsial serology. Twenty of the 35 cases had a positive serology. Of these 20 patients, 18 were already clinically diagnosed as having murine typhus. All except one were males and all were migrant workers. Majority of the patients were construction workers staying in containers where rats abound. The most consistent clinical features were high fever (100%) for a median period of seven days, headache (94%) and cough (47%). The white cell count was usually normal (74%) but thrombocytopenia was common (68%). Transaminitis was also common (90%) with the AST component higher than the ALT in half of the cases. Response to doxycycline therapy was rapid and most (88%) were afebrile by 72 hours. CONCLUSION: Typhus (notably murine type) can be confidently diagnosed from consistent clinical features supported by epidemiological and laboratory clues. Early recognition with the prompt treatment response will result in shorter hospital stay with decreased cost. Serological testing may only prove useful in difficult situations when the clinical diagnosis is less clear.

Adult↗
PubMed2000

Failure of routine HIV-1 tests in a case involving transmission with preseroconversion blood components during the infectious window period.

CONTEXT: Current screening practices for blood donations have been successful in reducing human immunodeficiency virus (HIV) transmission through receipt of contaminated blood products. However, HIV-infected blood donations made prior to seroconversion and before high levels of viral replication occur could test negative using both serologic antigen and antibody tests. Testing based on nucleic acid amplification (NAT) is being implemented to screen for HIV-infected blood donated during this period, yet the issue of single vs minipool donation screening remains unresolved. OBJECTIVES: To determine HIV-1 genetic linkage between virus in 2 HIV-1-infected recipients of blood components and virus in the donor, who was HIV antigen and antibody negative at the time of donation; to screen the blood donor's plasma with HIV NAT assays, including those currently proposed for use in US blood donation screening. DESIGN AND SETTING: Case study conducted in October 1997 involving the Communicable Disease Centre, Singapore General Hospital, and the Singapore Blood Transfusion Service, Singapore. SUBJECTS: The blood donor and the 2 recipients of donor platelets and red blood cells. MAIN OUTCOME MEASURES: Genetic analysis of the HIV-1 p17 coding region of gag and the C2V5 region of env to determine the genetic relatedness of virus from the donor and recipients; reactivity in quantitative and qualitative assays, and reactivity in donor screening HIV NAT assays in single donation and minipool screening contexts. RESULTS: Direct DNA sequencing demonstrated identical HIV-1 subtype E viral sequences in the donor and recipients. Based on comparisons of a qualitative and quantitative assay for HIV-1 RNA levels, a low level of viremia (range, 5-39 copies/mL in plasma) was estimated to be in the donor's undiluted blood at the time of donation. Additional testing using donor-screening NAT assays showed consistent detection of HIV RNA in the undiluted donor plasma whereas detection was inconsistent at the 1:16 and 1:24 dilution levels currently used in minipool screening of blood donations in the United States. CONCLUSIONS: Transmission of HIV from a blood donor to a platelet recipient and a red blood cell recipient occurred in the preseroconversion infectious window period. The viral load in the implicated donation was estimated to be less than 40 copies/mL of plasma. Current US minipool HIV NAT screening protocols may not be sufficiently sensitive to detect all infectious window-period donations. JAMA. 2000;284:210-214

AIDS Serodiagnosis↗
PubMed2000

Case report of Staphylococcus lugdunensis native valve endocarditis and review of the literature.

INTRODUCTION: Coagulase-negative staphylococci, commonly Staphylococcus epidermidis, cause 5% of native valve endocarditis. We describe a case due to Staphylococcus lugdunensis, a coagulase-negative staphylococcus identified in 1988, as a first report in Southeast Asia. It was previously misidentified as S. aureus because it is sometimes slide coagulase positive, but always tube coagulase negative, resulting in its delayed recognition as a pathogen. We also reviewed 36 other cases reported in the English literature from 1988 to 1999. CLINICAL PICTURE: Our patient was admitted 3 times over 4 months for unresolved weight loss and fever before the coagulase-negative staphylococcus bacteraemia was eventually considered significant. TREATMENT AND OUTCOME: He was treated with 4 weeks of high-dose intravenous penicillin and 2 weeks of gentamicin and did not require urgent valve replacement. CONCLUSION: A positive blood culture of coagulase-negative staphylococcus is not always a contaminant. S. lugdunensis can cause aggressive native valve endocarditis resulting in high mortality, especially without surgical intervention.

Adult↗
PubMed2000

Correlation of baseline quantitative plasma human immunodeficiency (HIV) type 1 RNA viral load with clinical status and CD4+ T-cell counts in treatment-naïve HIV-positive patients in Singapore.

INTRODUCTION: Quantitative measurement of plasma HIV-1 RNA viral load has been available in Singapore since 30 November 1996. This study investigates the relationship, in antiretroviral-naïve, HIV-positive Singapore residents, between the baseline HIV-1 RNA viral load and clinical status at the time of quantification. The association of HIV-1 RNA viral load with CD4+ T-cell counts was also studied. MATERIALS AND METHODS: HIV-1 RNA viral load was determined using Amplicor HIV-1 Monitor Test. One hundred and eighty subjects had baseline plasma HIV-1 RNA levels quantified during the period 30 November 1996 to 27 July 1998. They were classified into three clinical groups: A for asymptomatic infection (n = 110), B for symptomatic infection (n = 29) and C for AIDS (n = 41). RESULTS: The differences between mean HIV-1 RNA levels were statistically significant (P < 0.001) for groups A and B (mean difference = -0.61 log10), and for groups A and C (mean difference = -0.75 log10). However, there was no statistically significant difference (P = 0.68) between groups B and C (mean difference = -0.13 log10). Of those subjects with CD4+ T-cell counts measured within 30 days of viral load quantification, there were statistically significant negative correlations between HIV-1 viral load and CD4+ T-cell counts for groups A (n = 91, r = -0.536, P < 0.01) and C (n = 34, r = -0.446, P < 0.01) but not group B (n = 26, r = -0.297, P > 0.05). CONCLUSION: This suggest that the more advanced the phase of HIV infection, the higher the baseline plasma viral load and the lower the CD4+ T-lymphocyte counts.

Adult↗
PubMed1999

Outbreak of Nipah-virus infection among abattoir workers in Singapore.

BACKGROUND: In March 1999, an outbreak of encephalitis and pneumonia occurred in workers at an abattoir in Singapore. We describe the clinical presentation and the results of investigations in these patients. METHODS: Clinical and laboratory data were collected by systemic review of the case records. Serum and cerebrospinal fluid (CSF) samples were tested for IgM antibodies to Nipah virus with an IgM capture ELISA. Reverse-transcriptase PCR was done on the CSF and tissue samples from one patient who died. FINDINGS: Eleven patients were confirmed to have acute Nipah-virus infection based on raised IgM in serum. Nipah virus was identified by reverse transcriptase PCR in the CSF and tissue of the patient who died. The patients were all men, with a median age of 44 years. The commonest presenting symptoms were fever, headache, and drowsiness. Eight patients presented with signs of encephalitis (decreased level of consciousness or focal neurological signs). Three patients presented with atypical pneumonia, but one later developed hallucinations and had evidence of encephalitis on CSF examination. Abnormal laboratory findings included a low lymphocyte count (nine patients), low platelet count, low serum sodium, and high aspartate aminostransferase concentration (each observed in five patients). The CSF protein was high in eight patients and white-blood-cell count was high in seven. Chest radiography showed mild interstitial shadowing in eight patients. Magnetic resonance imaging (MRI) showed focal areas of increased signal intensity in the cortical white marker in all eight patients who were scanned. The nine patients with encephalitis received empirical treatment with intravenous aciclovir and eight survived. INTERPRETATION: Infection with Nipah virus caused an encephalitis illness with characteristic focal areas of increased intensity seen on MRI. Lung involvement was also common, and the disease may present as an atypical pneumonia.

Abattoirs↗
PubMed1999

Disseminated Penicillium marneffei infection: a report of five cases in Singapore.

Penicillium marneffei has emerged as an important opportunistic pathogen in HIV-infected patients in Southeast Asia. We report the first 5 cases of P. marneffei diagnosed in Singapore. All the patients were HIV-infected and were either Thai nationals or had frequently travelled to Thailand. Fever, weight loss, anaemia and papular skin lesions were common clinical manifestations in our patients, all of whom had the organism isolated from blood. Skin biopsy specimens showed histological evidence of P. marneffei in 2 patients. In 1 patient each, the organism grew in cultures of specimens from bone marrow and respiratory secretions. Amphotericin B therapy followed by itraconazole were used in 3 of our 5 patients and was associated with good clinical response and outcome.

AIDS-Related Opportunistic Infections↗