Adolescent ; Adult ; Age Factors ; Aged ; Child ; Child, Preschool ; Female ; Humans ; Malaria ; classification ; epidemiology ; prevention & control ; Male ; Middle Aged ; Singapore

Animals ; Birds ; Communicable Disease Control ; methods ; Disease Outbreaks ; prevention & control ; statistics & numerical data ; Health Planning ; Humans ; Influenza A Virus, H5N1 Subtype ; Influenza in Birds ; epidemiology ; virology ; Risk Factors ; Singapore ; epidemiology

INTRODUCTIONWe carried out an epidemiological review of cholera in Singapore to determine its trends and the factors contributing to its occurrence.

MATERIALS AND METHODSEpidemiological data of all notified cases of cholera maintained by the Communicable Diseases Division, Ministry of Health, for the period 1992 to 2007 were collated and analysed. Case-control studies were carried out in outbreaks to determine the source of infection and mode of transmission. Linear patterns in age and ethnic distribution of cholera cases were assessed using chi2 test for trend.

RESULTSThere were a total of 210 cholera cases reported between 1992 and 2007. The incidence of cholera declined from 17 cases in 1992 to 7 cases in 2007. About a quarter of the cases were imported from endemic countries in the region. Between 76% and 95% of the reported cases were local residents. Four elderly patients with comorbidities and who sought medical treatment late died, giving a case-fatality rate of 1.9%. Vibrio cholerae 01, biotype El Tor, serotype Ogawa, accounted for 83.8% of the cases. The vehicles of transmission identified in outbreaks included raw fi sh, undercooked seafood and iced drinks cross-contaminated with raw seafood.

CONCLUSIONWith the high standard of environmental hygiene and sanitation, a comprehensive epidemiological surveillance system and licensing and control of food establishments, cholera could not gain a foothold in Singapore despite it being situated in an endemic region. However, health education of the public on the importance of personal and food hygiene is of paramount importance in preventing foodborne outbreaks. Physicians should also maintain a high level of suspicion of cholera in patients presenting with severe gastroenteritis, especially those with a recent travel history to endemic countries.

Adolescent ; Child ; Child, Preschool ; Cholera ; microbiology ; mortality ; Disease Outbreaks ; statistics & numerical data ; Female ; Foodborne Diseases ; epidemiology ; prevention & control ; Humans ; Incidence ; Infant ; Infant, Newborn ; Male ; Middle Aged ; Population Surveillance ; Singapore ; epidemiology ; Vibrio cholerae O1 ; isolation & purification ; Young Adult

INTRODUCTIONWe reviewed the epidemiological features of rubella in Singapore and the impact of the national immunisation programme in raising the population herd immunity against rubella, with special reference to females in the reproductive age group, and in the elimination of congenital rubella syndrome (CRS).

MATERIALS AND METHODSEpidemiological data on all reported cases of rubella and CRS were obtained from the Communicable Diseases Division and Central Claims Processing System, respectively, at the Ministry of Health. Coverage of the childhood immunisation programme against rubella was based on the immunisation data maintained by the National Immunisation Registry, Health Promotion Board. To assess the herd immunity of the population against rubella, 4 serological surveys were conducted from 1989 to 1990, in 1993, 1998 and 2004.

RESULTSThe incidence of rubella has decreased significantly from the peak of 13.3 per 100,000 population in 1996 to 1.8 per 100,000 in 2007. CRS has virtually disappeared. With more than 92% to 93% of primary school leavers and preschool children annually vaccinated against rubella since 1976 and 1990, respectively, the level of susceptibility to rubella among women in the reproductive age group has gradually decreased from 44% in 1975 to 28% in 1985, and maintained at between 10% and 20% from 1987 to 1998. A considerable proportion (15.8%) of women 18 to 44 years of age remained susceptible to rubella infection in 2004.

CONCLUSIONRubella prevention and control has been successfully implemented. However, the relatively high level of susceptibility to rubella among women in the reproductive age group continues to be of concern. More public awareness and health educational efforts are needed and every opportunity should be taken to ensure that all susceptible women are identified and protected against the infection.

Adolescent ; Adult ; Child ; Child, Preschool ; Female ; Humans ; Immunization ; utilization ; Infant ; Infant, Newborn ; Male ; Middle Aged ; Population Surveillance ; Rubella Syndrome, Congenital ; epidemiology ; prevention & control ; Seroepidemiologic Studies ; Singapore ; epidemiology ; Young Adult

INTRODUCTION: We investigated the epidemiological features of the 2007 dengue outbreak to determine the factors that could have triggered it two years after the previous large outbreak in 2005.

METHODS: All laboratory-confirmed cases of dengue reported during the year, as well as entomological and virological data, were analysed.

RESULTS: A total of 8826 cases including 24 deaths were reported in 2007, giving an incidence of 192.3 cases per 100 000 residents and a case-fatality rate of 0.27%. The median age of the cases was 37 years (interquartile range 25 to 50), with an age range from two days to 101 years, which was higher than the median age of 31 years (interquartile range 20 to 42), with a range from four days to 98 years, in 2005. The overall Aedes premises index in 2007 was 0.68%, lower than the 1.15% observed in 2005. The predominant dengue serotype in 2007 was dengue virus DENV-2 which re-emerged with a clade replacement in early 2007, and overtook the predominant serotype (DENV-1) of 2005. Seroprevalence studies conducted in the three largest outbreak clusters revealed that 73.2% of residents with recent infection were asymptomatic.

DISCUSSION: With the exception of an increase in the median age of the cases, and a change in the predominant dengue serotype, the epidemiological features of the 2007 epidemic were largely similar to those of 2005. Singapore remains vulnerable to major outbreaks of dengue, despite sustained vector control measures to maintain a consistently low Aedes premises index.

INTRODUCTIONThe objective of the study was to determine the trend of malaria, the epidemiological characteristics, the frequency of local transmission and the preventive and control measures taken.

MATERIALS AND METHODSWe analysed the epidemiological records of all reported malaria cases maintained by the Communicable Diseases Division, Ministry of Health, from 1983 to 2007 and the Anopheles vector surveillance data collected by the National Environment Agency during the same period.

RESULTSThe annual incidence of reported malaria ranged from 2.9 to 11.1 per 100,000 population, with a sharp decline observed after 1997. There were 38 deaths, 92.1% due to falciparum malaria and 7.9% due to vivax malaria. Of the reported cases, 91.4% to 98.3% were imported, with about 90% originating from Southeast Asia and the Indian subcontinent. Among the various population groups with imported malaria, the proportion of cases involving work permit/employment pass holders had increased, while that of local residents had decreased. Between 74.8% and 95.1% of the local residents with imported malaria did not take personal chemoprophylaxis when they travelled overseas. Despite the extremely low Anopheles vector population, a total of 29 local outbreaks involving 196 cases occurred. Most of the larger outbreaks could be traced to foreign workers with imported relapsing vivax malaria and who did not seek medical treatment early. One of the outbreaks of 3 cases in 2007 was caused by Plasmodium knowlesi, a newly recognised simian malaria which was probably acquired in a forested area where long-tail macaques had been sighted.

CONCLUSIONSSingapore remains both vulnerable and receptive to the reintroduction of malaria and a high level of vigilance should be maintained indefinitely to prevent the re-establishment of endemicity. Medical practitioners should highlight the risk of malaria to travellers visiting endemic areas and also consider the possibility of simian malaria in a patient who has no recent travel history and presenting with daily fever spikes and with malaria parasite morphologically similar to that of P. malariae.

Adolescent ; Adult ; Animals ; Anopheles ; Child ; Child, Preschool ; Disease Outbreaks ; Emigrants and Immigrants ; Female ; Humans ; Incidence ; Infant ; Infant, Newborn ; Insect Vectors ; Malaria ; epidemiology ; prevention & control ; transmission ; Malaria, Falciparum ; epidemiology ; prevention & control ; transmission ; Malaria, Vivax ; epidemiology ; prevention & control ; transmission ; Male ; Middle Aged ; Plasmodium knowlesi ; Plasmodium malariae ; Population Surveillance ; Recurrence ; Retrospective Studies ; Risk Factors ; Singapore ; epidemiology ; Travel ; Young Adult

INTRODUCTIONWe reviewed the epidemiology of hand, foot and mouth disease (HFMD) in Singapore after the 2000 epidemic caused by Enterovirus 71 (EV71), with particular reference to the cyclical pattern, predominant circulating enteroviruses and impact of prevention and control measures in preschool centres.

MATERIALS AND METHODSWe analysed the epidemiological data from all clinical cases and deaths of HFMD diagnosed by medical practitioners and notified to the Ministry of Health, as well as laboratory data on enteroviruses detected among HFMD patients maintained by the Department of Pathology, Singapore General Hospital, and the Microbiology Laboratory, KK Women's and Children's Hospital from 2001 to 2007.

RESULTSThe incidence rate was highest in the 0 to 4 years old age group, with males being predominant. Three deaths were reported between January and February 2001. Nationwide epidemics occurred periodically; the predominating circulating virus was Coxsackievirus A16 (CA16) in the 2002, 2005 and 2007 epidemics, and EV71 in the 2006 epidemic. During the epidemic years between 2005 and 2007, 2 peaks were observed. The number of institutional outbreaks had increased 10-fold from 167 in 2001 to 1723 in 2007, although most of these outbreaks were rapidly brought under control with an attack rate of less than 10%.

CONCLUSIONHFMD remains an important public health problem in Singapore with the annual incidence rate per 100,000 population increasing from 125.5 in 2001 to 435.9 in 2007, despite stringent measures taken in preschool centres to prevent the transmission of infection. A high degree of vigilance should be maintained over the disease situation, in particular, surveillance of EV 71 which continues to cause severe complications and deaths in the region.

Adolescent ; Adult ; Child ; Child, Preschool ; Communicable Disease Control ; methods ; Disease Outbreaks ; prevention & control ; statistics & numerical data ; Female ; Hand, Foot and Mouth Disease ; epidemiology ; prevention & control ; Humans ; Infant ; Infant, Newborn ; Male ; Middle Aged ; Retrospective Studies ; Singapore ; epidemiology ; Young Adult

INTRODUCTIONSingapore has experienced remarkable socioeconomic progress over the last few decades, with a corresponding rise in standards of sanitation and living conditions. We undertook a study to describe its epidemiological trends of hepatitis A over the last 2 decades.

MATERIALS AND METHODSWe analysed the epidemiological data on all laboratory-confirmed cases of hepatitis A from 1990 to 2009. We also described 3 outbreaks which occurred in 1991, 1992 and 2002. To determine the changing prevalence of hepatitis A virus (HAV) infection, we compared the findings from a seroepidemiological study conducted in 1993 with earlier surveys in 1975 and 1984/1985.

RESULTSThe incidence of indigenous hepatitis A cases per 100,000 population declined significantly from 1.8 in 1989 to 0.7 in 2009, and more than half were imported. While majority of the imported cases were Singapore residents, the proportion of imported cases among Singapore residents had decreased significantly. Most of the Singapore residents contracted the disease from Southeast Asia and the Indian subcontinent. The overall prevalence of HAV infection in the population declined from 31.8% in 1984/85 to 25.9% in 1993.

CONCLUSIONThe incidence and seroprevalence of hepatitis A in Singapore are comparable to other developed countries. As Singapore is situated in a region highly endemic for HAV, it is very vulnerable to the introduction of the disease because of the high volume of regional travel and import of food, especially shellfish. While we note that there have been no further shellfish-associated outbreaks since 2002, sustained vigilance, strict control of food import by the authorities and public health education on the risk of consuming shellfish, especially cockles, raw and half-cooked, should be maintained.

Adolescent ; Adult ; Child ; Child, Preschool ; Disease Outbreaks ; Female ; Hepatitis A ; epidemiology ; etiology ; Hepatitis A Virus, Human ; isolation & purification ; Humans ; Immunoglobulin G ; immunology ; Infant ; Male ; Middle Aged ; Seroepidemiologic Studies ; Shellfish ; virology ; Singapore ; epidemiology ; Young Adult

INTRODUCTIONSingapore is a transition country in Southeast Asia that is both vulnerable and receptive to the introduction and re-introduction of imported communicable diseases.

MATERIALS AND METHODSFor a 10-year period between 1998 and 2007 we studied the trend, epidemiological characteristics, proportion of imported versus local transmission of malaria, viral hepatitis (hepatitis A and E), enteric fevers (typhoid and paratyphoid), cholera, chikungunya and SARS.

RESULTSOf a total of 4617 cases of the above selected diseases notified in Singapore, 3599 (78.0%) were imported. The majority of the imported cases originated from Southeast Asia and the Indian subcontinent. Malaria constituted the largest bulk (of which 95.9% of the 2126 reported cases were imported), followed by hepatitis A (57.1% of 1053 cases imported), typhoid (87.6% of 596 cases imported), paratyphoid (87.6% of 241 cases imported), and hepatitis E (68.8% of 231 cases imported). Furthermore, there were 14 cases of imported cholera, 6 cases of imported severe acute respiratory syndrome (SARS) and 13 cases of imported chikungunya.

CONCLUSIONThis study underlines that diseases such as malaria, viral hepatitis and enteric fever occur in Singapore mainly because of importation. The main origin of importation was South and Southeast Asia. The proportion of imported diseases in relation to overall passenger traffic has decreased over the past 10 years.

Communicable Diseases ; epidemiology ; etiology ; transmission ; Disease Outbreaks ; statistics & numerical data ; Female ; Humans ; Male ; Population Surveillance ; Singapore ; epidemiology ; Travel ; Young Adult

INTRODUCTIONWe presented the findings from 2 seroprevalence studies conducted 6 years apart, so as to determine changes in the hepatitis B surface antigen (HBsAg) positivity rate and immunity to hepatitis B virus (HBV) among Singapore residents aged 18 to 69 years, and to assess the impact of a 4-year catch-up hepatitis B immunisation programme for adolescents and young adults launched in 2001.

MATERIALS AND METHODSTwo hepatitis B seroprevalence studies (HBSS) were conducted in 1999 and 2005 based on stored blood samples collected from 4698 participants aged 18 to 69 years during the national health survey (NHS) 1998 and from 3460 participants during the NHS 2004, respectively. Serology for HBsAg, hepatitis B e antigen (HBeAg) and antibody to HBsAg (anti-HBs) were tested by enzyme immunoassay in HBSS 1999 and electrochemiluminescence in HBSS 2005.

RESULTSThe overall age-standardised prevalence of HBsAg among Singapore residents aged 18 to 69 years decreased significantly from 4.0% in HBSS 1999 to 2.8% in HBSS 2005 (P = 0.002). The age-standardised prevalence of HBsAg in males (4.9% in 1999) and Chinese (4.7% in 1999) both decreased significantly to 2.7% and 2.8%, respectively in 2005. The overall age-standardised population immunity to HBV (anti-HBs >10 mIU/ml) increased from 39.7% in 1999 to 42.1% in 2005 (P = 0.019). In particular, the age-specific prevalence of anti-HBs showed a significant increase among those in the age group of 18 to 29 years from 27.9% in 1999 to 41.7% in 2005 (P <0.001) and among those in the age group of 30 to 39 years from 39.9% in 1999 to 44.7% in 2005 (P = 0.021).

CONCLUSIONThere was an overall decline in the HBsAg positivity rate as well as an overall increase in population immunity to HBV. Following the 4-year catch-up immunisation programme, there was a significant increase in the immunity to HBV infection in the younger population aged 18 to 29 years.

Adolescent ; Adult ; Age Factors ; Aged ; Biomedical Research ; Confidence Intervals ; Female ; Health Surveys ; Hepatitis B ; blood ; diagnosis ; epidemiology ; immunology ; Hepatitis B Surface Antigens ; immunology ; Hepatitis B Vaccines ; Humans ; Immunization Programs ; Immunoenzyme Techniques ; Male ; Middle Aged ; Population Surveillance ; Risk Factors ; Seroepidemiologic Studies ; Singapore ; epidemiology ; Young Adult