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Annelies Wilder-Smith

Publications and source records attributed to Annelies Wilder-Smith.

At least 19 recordsLinked to original sources
PubMed2006

Illness in travelers visiting friends and relatives: a review of the GeoSentinel Surveillance Network.

Travelers returning to their country of origin to visit friends and relatives (VFRs) have increased risk of travel-related health problems. We examined GeoSentinel data to compare travel characteristics and illnesses acquired by 3 groups of travelers to low-income countries: VFRs who had originally been immigrants (immigrant VFRs), VFRs who had not originally been immigrants (traveler VFRs), and tourist travelers. Immigrant VFRs were predominantly male, had a higher mean age, and disproportionately required treatment as inpatients. Only 16% of immigrant VFRs sought pretravel medical advice. Proportionately more immigrant VFRs visited sub-Saharan Africa and traveled for >30 days, whereas tourist travelers more often traveled to Asia. Systemic febrile illnesses (including malaria), nondiarrheal intestinal parasitic infections, respiratory syndromes, tuberculosis, and sexually transmitted diseases were more commonly diagnosed among immigrant VFRs, whereas acute diarrhea was comparatively less frequent. Immigrant VFRs and traveler VFRs had different demographic characteristics and types of travel-related illnesses. A greater proportion of immigrant VFRs presented with serious, potentially preventable travel-related illnesses than did tourist travelers.

Adolescent↗
PubMed2006

Travel characteristics and health practices among travellers at the travellers' health and vaccination clinic in Singapore.

INTRODUCTION: Singapore has a fast-growing travel industry, but few studies have been done on travel characteristics and travel health practices. This study describes the profile and healthseeking behaviour of travellers attending a travel health clinic in Singapore. MATERIALS AND METHODS: A cross-sectional survey was conducted on travellers attending the Traveller's Health and Vaccination Centre (THVC) between September and November 2002 using a standardised questionnaire. Information obtained included individual demographic and medical information, travel patterns, vaccination status and travel health practices. RESULTS: Four hundred and ninetyfive (74%) eligible travellers seen at THVC responded to the questionnaire. Their mean age was 36 years; 77% were professionals, managers, executives, and businessmen, students, and white collar workers. Asia was the main travel destination, and most travelled for leisure and resided in hotels or hostels. The median duration of travel was 16 days. Although >90% had previously travelled overseas, only 20% had previously sought pre-travel advice. Malays were significantly underrepresented (P < 0.01); and Caucasians and Eurasians were significantly more likely (P < 0.01) to have previously sought pre-travel advice compared with Chinese, Indians and Malays. Factors associated with seeking pre-travel advice included travel outside of Asia, especially Africa and South America. CONCLUSION: Singaporean travellers travel more often to cities rather than rural areas, compared with non-Asian travellers. Asia is the preferred destination, and travel outside of Asia is perceived as more risky and is associated with seeking pre-travel advice and vaccinations. Travel patterns and behaviours need to be taken into account when developing evidence-based travel medicine in Asia.

Adult↗
PubMed2005

Distinguishing dengue fever from other infections on the basis of simple clinical and laboratory features: application of logistic regression analysis.

BACKGROUND: Dengue fever is a frequent cause of admission to hospital in South East Asia, however many of the clinical characteristics and abnormalities on laboratory investigations at presentation are found in other common infections. OBJECTIVES: To describe the clinical and laboratory features of dengue fever and other common febrile illnesses in Singapore. STUDY DESIGN: We performed a prospective study of consecutive adult admissions to an infectious diseases hospital. Logistic regression analysis was used to identify symptoms, physical signs and laboratory features that differentiated dengue fever from other febrile illnesses within the first 2 days of admission. RESULTS: Of the 381 patients studied, 148 had serologically confirmed dengue fever. Most of these had uncomplicated dengue fever, and only 9% had dengue haemorrhagic fever. A model based on clinical features alone (including a variety of cutaneous signs, pulse rate and the presence of pharyngeal injection) was able to differentiate dengue fever from other infections with a sensitivity of 74% and specificity of 79%. A model based on clinical features (rash) and laboratory parameters (white cell count, haemoglobin, prothrombin time, creatinine and bilirubin levels), achieved a sensitivity of 84% and specificity of 85%. CONCLUSIONS: A combination of simple clinical and laboratory parameters are potentially able to predict dengue fever with a high level of accuracy in adults presenting to hospital with febrile illnesses in Singapore.

Adult↗
PubMed2005

The severe acute respiratory syndrome: impact on travel and tourism.

SARS and travel are intricately interlinked. Travelers belonged to those primarily affected in the early stages of the outbreak, travelers became vectors of the disease, and finally, travel and tourism themselves became the victims. The outbreak of SARS created international anxiety because of its novelty, its ease of transmission in certain settings, and the speed of its spread through jet travel, combined with extensive media coverage. The psychological impacts of SARS, coupled with travel restrictions imposed by various national and international authorities, have diminished international travel in 2003, far beyond the limitations to truly SARS hit areas. Governments and press, especially in non SARS affected areas, have been slow to strike the right balance between timely and frequent risk communication and placing risk in the proper context. Screening at airport entry points is costly, has a low yield and is not sufficient in itself. The low yield in detecting SARS is most likely due to a combination of factors, such as travel advisories which resulted in reduced travel to and from SARS affected areas, implementation of effective pre-departure screening at airports in SARS-hit countries, and a rapid decline in new cases at the time when screening was finally introduced. Rather than investing in airport screening measures to detect rare infectious diseases, investments should be used to strengthen screening and infection control capacities at points of entry into the healthcare system. If SARS reoccurs, the subsequent outbreak will be smaller and more easily contained if the lessons learnt from the recent epidemic are applied. Lessons learnt during the outbreak in relation to international travel will be discussed.

China↗
PubMed2005

Serological evidence for the co-circulation of multiple dengue virus serotypes in Singapore.

We did a seroepidemiological study to determine the circulating dengue virus serotypes and the extent to which the Singapore population has been exposed to multiple dengue virus serotypes, using the plaque reduction neutralization assay (PRNT). Of 164 enrolled subjects aged between 18-30 years, 49 subjects (29.8%) were PRNT positive for at least one dengue serotype. The seroprevalence was 39 (23.8%) for dengue virus serotype 1, 37 (22.6%) for type 2, 43 (26.2%) for type 3, and 30 (18.3%) for type 4. Of the 49 subjects with PRNT-positive dengue virus results, 28 (57.1%) were positive to all four virus serotypes, seven (14.3%) to three serotypes, two (4%) to two serotypes, and 12 (24.5%) to a single serotype. All four dengue virus serotypes circulate in Singapore, and a substantial proportion of the adult population in Singapore had exposure to more than one dengue virus serotype. In spite of multiple circulating types, the rate of dengue haemorrhagic fever is low in Singapore.

Adolescent↗
PubMed2005

High risk of Mycobacterium tuberculosis infection during the Hajj pilgrimage.

INTRODUCTION: Annually more than 2 million pilgrims from all over the world attend the Hajj in Saudi Arabia. Overcrowding during this pilgrimage leads to a high risk of transmission of airborne infectious diseases. Tuberculosis (TB) is common among hospitalized pilgrims, but the overall risk of acquiring Mycobacterium tuberculosis infection during this pilgrimage is not known. We conducted a prospective study to assess the risk of M. tuberculosis infection among Hajj pilgrims. METHODS: We measured the immune response to TB antigens using a whole-blood assay (QuantiFERON TB assay) prior to departure and 3 months after return from the Hajj pilgrimage. RESULTS: Of 357 paired assays, 149 pilgrims were negative prior to the Hajj and 15 (10%) of these had a significant rise in immune response to TB antigens. CONCLUSIONS: Pilgrims may be at high risk of acquiring M. tuberculosis infection during the Hajj. This has significant public health implications for TB control in countries with large Muslim populations.

Adolescent↗
PubMed2005

Meningococcal disease in international travel: vaccine strategies.

International travel and migration facilitate the rapid intercontinental spread of meningococcal disease. Serogroup A, and to a lesser extent serogroup C, have been responsible for pandemics in the past (mainly in Africa), but in recent years there was an international outbreak due to W135 related to the Hajj pilgrimage. The high carriage rates, persistence and transmissibility, in combination with the high case fatality rate of the Hajj-associated W135 outbreak clone, certainly raise considerable concern about the public health consequences of widespread dissemination of this organism and the potential for future epidemics. Indeed, the now evolving W135 epidemic in Africa mandates that the bivalent meningococcal vaccine should be replaced by the tetravalent meningococcal vaccine, covering A, C, Y and W135 serogroups. The currently available polysaccharide tetravalent meningococcal vaccine, albeit associated with high seroconversion and efficacy rates, has several shortcomings: it is not immunogenic in young children, duration of protective immunity is short, and it has minimal or no effect on nasopharyngeal carriage and therefore transmission of the organism. Immunogenicity of polysaccharide vaccines can be improved by chemical conjugation to a protein carrier, thereby eliciting a T-cell-dependent antibody response. In contrast to polysaccharide vaccines, conjugate vaccines are immunogenic in young infants, induce long-term protection, and reduce nasopharyngeal carriage. The tetravalent conjugate vaccine will be a leap forward in the control of meningococcal epidemics in affected countries. It will also boost the uptake of meningococcal vaccines in travelers, because the duration of protection is longer and it eliminates the problem of immune hyporesponsiveness of serogroup C with repeated dosing. The small risk of travel-associated disease for the general traveler and the unpredictable nature of epidemics make it difficult to provide evidence-based vaccine recommendations. The current recommendation is to vaccinate all Hajj pilgrims, travelers to areas with current outbreaks, travelers to the sub-Saharan meningitis belt, and high-risk individuals (i.e., those with immunodeficiencies).

Disease Outbreaks↗
PubMed2005

Asymptomatic SARS coronavirus infection among healthcare workers, Singapore.

We conducted a study among healthcare workers (HCWs) exposed to patients with severe acute respiratory syndrome (SARS) before infection control measures were instituted. Of all exposed HCWs, 7.5% had asymptomatic SARS-positive cases. Asymptomatic SARS was associated with lower SARS antibody titers and higher use of masks when compared to pneumonic SARS.

Adult↗
PubMed2005

Risk of respiratory infections in health care workers: lessons on infection control emerge from the SARS outbreak.

Close proximity of persons together with handling of human secretions (eg respiratory secretions) make health care workers (HCW) particularly vulnerable to transmission of droplet-transmitted respiratory infections. This was tragically highlighted during the international outbreak of severe acute respiratory syndrome (SARS) in 2003 with attack rates of more than 50% in HCW. The purpose of this article is to review common airborne and droplet-transmitted bacterial and viral respiratory tract infections with regard to their impact on health care workers. Lessons need to be learned from the SARS epidemic. The three main strategies to prevent or control occupationally acquired infections are relatively simple and cost-effective-droplet and contact precautions and for some pathogens also vaccination. Enforced implementation of stringent droplet precautions during the SARS crisis should be maintained; and this will most likely have a major additional impact on other nosocomial infections. Employee health services should proactively and creatively devise delivery systems that enhance compliance with vaccination programs for all health care workers. Hospital surveillance should be expanded to all respiratory diseases to facilitate early detection of nosocomial outbreaks, and this should also include surveillance of all HCW. Integrated syndromic and virological surveillance systems set up during the SARS epidemic will also further our understanding of other respiratory infections in the hospital setting. Even if pursuing early diagnosis for unspecific respiratory illnesses is expensive, identification of the causative organism may reduce unnecessary isolation, contact tracing and anxiety, in particular during an outbreak situation. We have a duty to protect our health care workers.

Cross Infection↗
PubMed2004

Use of simple laboratory features to distinguish the early stage of severe acute respiratory syndrome from dengue fever.

BACKGROUND: The diagnosis of severe acute respiratory syndrome (SARS) is difficult early in the illness, because its presentation resembles that of other nonspecific viral fevers, such as dengue. Dengue fever is endemic in many of the countries in which the large SARS outbreaks occurred in early 2003. Misdiagnosis may have serious public health consequences. We aimed to determine simple laboratory features to differentiate SARS from dengue. METHODS: We compared the laboratory features of 55 adult patients with SARS at presentation (who were all admitted before radiological changes had occurred) and 147 patients with dengue. Features independently predictive of dengue were modeled by multivariate logistic regression to create a diagnostic tool with 100% specificity for dengue. RESULTS: Multivariate analysis identified 3 laboratory features that together are highly predictive of a diagnosis of dengue and able to rule out the possibility of SARS: platelet count of <140 x 10(9) platelets/L, white blood cell count of <5x10(9) cells/L, and aspartate aminotransferase level of >34 IU/L. A combination of these parameters has a sensitivity of 75% and a specificity of 100%. CONCLUSIONS: Simple laboratory data may be helpful for the diagnosis of disease in adults admitted because of fever in areas in which dengue is endemic when the diagnosis of SARS needs to be excluded. Application of this information may help to optimize the use of isolation rooms for patients presenting with nonspecific fever.

Aspartate Aminotransferases↗
PubMed2004

Seroepidemiology of dengue in the adult population of Singapore.

Urbanization is one of the reasons for the resurgence of dengue in tropical and subtropical countries. We conducted a cross-sectional seroepidemiological study in Singapore to determine the extent at which the Singapore population has been exposed to dengue infections. Dengue antibodies were measures with PanBio Dengue. Of 298 enrolled subjects (age 18-45), 133 (45%) had a positive dengue serology. In multivariate analysis, age and nationality (Singaporean vs non-Singaporean Asians) were found to be significant independent predictors. The odds ratio of dengue seroprevalence increased by 4.13 (95% CI: 2.88-5.93) for every 10 year increase in age. Dengue infections remain a major problem in Singapore.

Adolescent↗
PubMed2003

High incidence of pertussis among Hajj pilgrims.

Prolonged cough occurs in a large proportion of the 2 million pilgrims who participate in the annual Hajj in Saudi Arabia. In a prospective seroepidemiological study to determine the incidence of pertussis among 358 adult pilgrims, 5 (1.4%) were found to have acquired pertussis (defined as prolonged cough and a >4-fold increase in the level of immunoglobulin G to whole-cell pertussis antigen). Of the 40 pilgrims who had no pre-Hajj immunity to pertussis, 3 (7.5%) acquired pertussis. Administration of acellular pertussis vaccine to pilgrims before the Hajj should be considered to address this problem.

Adolescent↗
PubMed2003

Hajj-associated outbreak strain of Neisseria meningitidis serogroup W135: estimates of the attack rate in a defined population and the risk of invasive disease developing in carriers.

An outbreak of disease due to Neisseria meningitidis serogroup W135 (W135) occurred in 2000 and 2001 among pilgrims returning from the annual Islamic pilgrimage to Saudi Arabia (the Hajj) and in their contacts. For the Hajj in 2000, the attack rate of W135 disease was 25 cases per 100,000 pilgrims. After the introduction of quadrivalent meningococcal vaccine for the Hajj in 2001, no pilgrim developed W135 disease. The estimated attack rates for household contacts of returning pilgrims were 18 cases and 28 cases per 100,000 contacts for the years 2000 and 2001, respectively. On the basis of rates of transmission of W135 carriage and national epidemiological data, the risk that an unvaccinated household contact who had acquired W135 carriage would develop invasive meningococcal disease was estimated to be 1 case per 70 acquisitions. Public health policies to protect household contacts of Hajj pilgrims need to be implemented.

Adolescent↗
PubMed2003

Meningococcal disease and travel.

Meningococcal disease continues to be a worldwide problem. This review examines the impact meningococcal disease has on international travel and vice versa the impact international travel has on the intercontinental spread of meningococci. The risk of meningococcal disease to the endemic population differs from that of travellers. The best documented risk of meningococcal disease among travellers has been in Hajj pilgrims for Mecca and Madina in Saudi Arabia. In response to the recent Hajj associated outbreak of W135 meningococcal disease, quadrivalent meningococcal vaccine (against serogroups A/C/Y/W135) became a visa requirement. In view of increasing worldwide reports of Y and W135 meningococcal disease, there should be a switch in recommendation from the bivalent (against A& C) to the quadrivalent vaccine for all travellers.

Disease Outbreaks↗
PubMed2003

W135 meningococcal carriage in association with the Hajj pilgrimage 2001: the Singapore experience.

An international outbreak among pilgrims returning from the Hajj (pilgrimage to Mecca) and their close contacts was caused by W135 Neisseria meningitidis. In Singapore, this strain is a new emerging problem, clearly associated with this outbreak. We investigated the extent of transmission of N. meningitidis in Hajj pilgrims and their contacts, in order to provide evidence for developing a rational public health policy. We found a high acquisition rate of W135 N. meningitidis in Singaporean pilgrims during the Hajj with substantial transmission to their household contacts. These findings would support a policy of eradication of pharyngeal carriage in returning pilgrims to prevent introduction and dissemination of meningococci.

Carrier State↗
PubMed2003

Low risk of transmission of severe acute respiratory syndrome on airplanes: the Singapore experience.

The risk of transmission of severe acute respiratory syndrome (SARS) on airplanes is of major concern to the public and airline industry. We examined data from flights to Singapore with SARS patients on board in order to assess this risk. In-flight transmission occurred only in one of the three flights with symptomatic SARS patients on board. The incidence was estimated to be 1 out of 156 passengers. The risk of in-flight transmission of SARS appears to be far lower than that reported for influenza, but may be increased with superspreaders on board.

Aircraft↗