Clinical Characteristics of Patients Hospitalized with Coronavirus Disease, Thailand

Among 11 patients in Thailand infected with severe acute respiratory syndrome coronavirus 2, we detected viral RNA in upper respiratory specimens a median of 14 days after illness onset and 9 days after fever resolution. We identified viral co-infections and an asymptomatic person with detectable virus RNA in serial tests. We describe implications for surveillance.

Vaccination with ALVAC and AIDSVAX to prevent HIV-1 infection in Thailand

BACKGROUND

The development of a safe and effective vaccine against the human immunodeficiency virus type 1 (HIV-1) is critical to pandemic control.

METHODS

In a community-based, randomized, multicenter, double-blind, placebo-controlled efficacy trial, we evaluated four priming injections of a recombinant canarypox vector vaccine (ALVAC-HIV [vCP1521]) plus two booster injections of a recombinant glycoprotein 120 subunit vaccine (AIDSVAX B/E). The vaccine and placebo injections were administered to 16,402 healthy men and women between the ages of 18 and 30 years in Rayong and Chon Buri provinces in Thailand. The volunteers, primarily at heterosexual risk for HIV infection, were monitored for the coprimary end points: HIV-1 infection and early HIV-1 viremia, at the end of the 6-month vaccination series and every 6 months thereafter for 3 years.

RESULTS

In the intention-to-treat analysis involving 16,402 subjects, there was a trend toward the prevention of HIV-1 infection among the vaccine recipients, with a vaccine efficacy of 26.4% (95% confidence interval [CI], -4.0 to 47.9; P=0.08). In the per-protocol analysis involving 12,542 subjects, the vaccine efficacy was 26.2% (95% CI, -13.3 to 51.9; P=0.16). In the modified intention-to-treat analysis involving 16,395 subjects (with the exclusion of 7 subjects who were found to have had HIV-1 infection at baseline), the vaccine efficacy was 31.2% (95% CI, 1.1 to 52.1; P=0.04). Vaccination did not affect the degree of viremia or the CD4+ T-cell count in subjects in whom HIV-1 infection was subsequently diagnosed.

CONCLUSIONS

This ALVAC-HIV and AIDSVAX B/E vaccine regimen may reduce the risk of HIV infection in a community-based population with largely heterosexual risk. Vaccination did not affect the viral load or CD4+ count in subjects with HIV infection. Although the results show only a modest benefit, they offer insight for future research. (ClinicalTrials.gov number, NCT00223080.)

Incidence, seasonality and mortality associated with influenza pneumonia in Thailand: 2005-2008

BACKGROUND

Data on the incidence, seasonality and mortality associated with influenza in subtropical low and middle income countries are limited. Prospective data from multiple years are needed to develop vaccine policy and treatment guidelines, and improve pandemic preparedness.

METHODS

During January 2005 through December 2008, we used an active, population-based surveillance system to prospectively identify hospitalized pneumonia cases with influenza confirmed by reverse transcriptase-polymerase chain reaction or cell culture in 20 hospitals in two provinces in Thailand. Age-specific incidence was calculated and extrapolated to estimate national annual influenza pneumonia hospital admissions and in-hospital deaths.

RESULTS

Influenza was identified in 1,346 (10.4%) of pneumonia patients of all ages, and 10 influenza pneumonia patients died while in the hospital. 702 (52%) influenza pneumonia patients were less than 15 years of age. The average annual incidence of influenza pneumonia was greatest in children less than 5 years of age (236 per 100,000) and in those age 75 or older (375 per 100,000). During 2005, 2006 and 2008 influenza A virus detection among pneumonia cases peaked during June through October. In 2007 a sharp increase was observed during the months of January through April. Influenza B virus infections did not demonstrate a consistent seasonal pattern. Influenza pneumonia incidence was high in 2005, a year when influenza A(H3N2) subtype virus strains predominated, low in 2006 when A(H1N1) viruses were more common, moderate in 2007 when H3N2 and influenza B co-predominated, and high again in 2008 when influenza B viruses were most common. During 2005-2008, influenza pneumonia resulted in an estimated annual average 36,413 hospital admissions and 322 in-hospital pneumonia deaths in Thailand.

CONCLUSION

Influenza virus infection is an important cause of hospitalized pneumonia in Thailand. Young children and the elderly are most affected and in-hospital deaths are more common than previously appreciated. Influenza occurs year-round and tends to follow a bimodal seasonal pattern with substantial variability. The disease burden varies significantly from year to year. Our findings support a recent Thailand Ministry of Public Health (MOPH) decision to extend annual influenza vaccination to older adults and suggest that children should also be targeted for routine vaccination.

Bacterial meningitis incidence in Thai children estimated by a rapid assessment tool (RAT)

Acute bacterial meningitis is an important cause of morbidity and mortality in children. To estimate the incidence of meningitis caused by all types of bacteria in Thai children under five years of age, data were collected using a rapid assessment tool (RAT) and analyzed. Clinical and laboratory data from suspected meningitis cases for a one-year period were retrospectively collected from 5 selected catchment areas located in the 4 regions of the country. Adjusted incidences of confirmed bacterial meningitis were calculated based on laboratory quality and lumbar puncture rates. Seventy-five suspected meningitis cases were identified among 305,023 children under age five in the catchment areas, with an unadjusted incidence of 24.6 per 100,000. Of these, 66.2, 55.9, and 33.8% were unconfirmed bacterial, purulent, and confirmed bacterial meningitis cases, respectively. Among the confirmed bacterial meningitis cases, 39.1, 26.1, 21.7 and 13.0% were caused by Haemophilus influenzae type B, gram-positive cocci, gram-negative bacilli, and Neisseria meningitidis, respectively. After adjusting based on the RAT application, the incidence of confirmed bacterial meningitis was about double that of the unadjusted incidence. This study gives an interval of possible incidences of bacterial meningitis in children under age five, which is between the unadjusted (low estimate) and adjusted (high estimate) incidences.

Human metapneumovirus reinfection among children in Thailand determined by ELISA using purified soluble fusion protein

BACKGROUND

Human metapneumovirus (hMPV) is a newly discovered paramyxovirus that causes acute respiratory illness. Despite apparent near-universal exposure during early childhood, immunity is transient.

METHODS

An indirect screening enzyme-linked immunosorbent assay using a recombinant soluble fusion (F) glycoprotein derived from hMPV was used to test for anti-F IgG in 1,380 pairs of acute- and convalescent-stage serum samples collected from children in Kamphaeng Phet, Thailand.

RESULTS

Of the 1,380 serum sample pairs tested, 1,376 (99.7%) showed evidence of prior infection with hMPV. Sixty-six paired specimens demonstrated a >or=4-fold rise in titer, for an overall reinfection rate of 4.9%. Two children demonstrated evidence of an initial infection. Forty-eight of the 68 new infections or reinfections occurred in 2000, accounting for 13.2% of all nonflaviviral febrile illnesses in the study population in that year. Of 68 positive cases, 85.3% complained of cough and 66.2% complained of rhinorrhea, compared with 61.4% and 49.0% of negative cases, respectively (P < .01). All positive samples were also tested for an increase in titer of antibodies to respiratory syncytial virus F, and 27% exhibited a >or=4-fold rise.

CONCLUSION

These results demonstrate that hMPV reinfections cause illness at a rate equal to that seen for initial infections. hMPV may have a more significant impact in older children than previously realized and may be the cause of significant outbreaks in this population.

Response to avian influenza and preparedness for pandemic influenza: Thailand's experience

Thailand has been struggling to control and prevent H5N1 avian influenza on both the animal health and public health fronts. Prevention and control programs for animals and humans are improving, with infections in poultry currently under control and no human cases seen in 2007. In awareness of the risk of an influenza pandemic, Thailand is joining global efforts in pandemic influenza preparedness. The national preparedness plan highlights building of national capacity for self-reliance and regional/international cooperation. Public health response to avian influenza and pandemic preparedness benefit significantly from the experience of responses to severe acute respiratory syndrome. This underlines the need to strengthen infrastructure and manpower, ensure public confidence and cooperation, secure maximum government advocacy and support, and forge multi-sector and international cooperation.

Burden of symptomatic dengue infection in children at primary school in Thailand: a prospective study

BACKGROUND

Dengue viruses are a major cause of morbidity and mortality in tropical and subtropical areas. Our aim was to assess prospectively the burden of dengue-related illness in children in Thailand.

METHODS

We did a prospective study in a cohort of children at primary school in northern Thailand from 1998 to 2002. We assessed the burden of dengue illness as disability-adjusted life years (DALYs) and patient costs per illness.

FINDINGS

Dengue accounted for 328 (11%) of the 3056 febrile cases identified in 2114 children during the study period. The mean burden of dengue was 465.3 (SD 358.0; range 76.5-954.0) DALYs per million population per year, accounting for about 15% of DALYs lost to all febrile illnesses (3213.1 [SD 2624.2] DALYs per million per year). Non-hospitalised patients with dengue illnesses represented a substantial proportion of the overall burden of disease, with 44-73% of the total DALYs lost to dengue each year due to such illness. The infecting dengue serotype was an important determinant of DALYs lost: DEN4 was responsible for 1% of total DALYs lost, DEN1 for 9%, DEN2 for 30%, and DEN3 for 29%.

INTERPRETATION

Use of prospective data to estimate the burden of disease shows that most DALYs lost to dengue illness were the result of non-hospitalised illnesses of long duration. Thus, inclusion of non-hospitalised cases is critical to accurately assess the total burden of dengue illness.

Antibody‐Dependent Cellular Cytotoxicity Mediated by Plasma Obtained before Secondary Dengue Virus Infections: Potential Involvement in Early Control of Viral Replication

BACKGROUND

Preexisting dengue virus (DV)-specific antibodies from prior heterologous DV infection may have several effects in secondary DV infection. These antibodies may mediate protective effects by means of antibody-dependent cellular cytotoxicity (ADCC), in which virus-specific antibodies bind to the surface of heterologous DV-infected cells and mediate natural killer cell lysis. In the present study, we examined the ability of plasma obtained before secondary DV infection to induce ADCC of DV-infected cells.

METHODS

Plasma samples were obtained before DV2 or DV3 infection in a prospective cohort study of Thai schoolchildren. The ADCC activity in the plasma samples was measured by (51)Cr-release assay, using persistently DV2- or DV3-infected Raji cells as targets.

RESULTS

ADCC activity in plasma obtained before secondary infection directly correlated with neutralizing antibody titers, anti-DV immunoglobulin G1 levels, and a multitypic 50% plaque reduction neutralization test pattern. ADCC activity in pre-secondary DV3 infection plasma samples inversely correlated with plasma viremia levels, but no such correlation was seen in pre-secondary DV2 infection plasma samples. ADCC activity did not correlate with disease severity in subsequent secondary DV2 or DV3 infection but was lowest in plasma from patients with dengue hemorrhagic fever due to secondary DV3 infection.

CONCLUSIONS

ADCC may contribute to the early control of secondary DV3 viremia in vivo.

The incidence of pneumonia in rural Thailand

Background

Pneumonia continues to be a leading infectious disease killer, yet accurately measuring incidence remains a challenge. In 2002, Thailand began active, population-based surveillance for radiographically confirmed pneumonia in Sa Kaeo Province.

Methods

Full-time surveillance officers conducted active case ascertainment at every hospital, and routine audits and a community cluster survey promoted complete and accurate reporting. A case of pneumonia was defined as acute infection with signs or symptoms of lower respiratory tract infection and evidence of new infiltrates. An independent panel of radiologists reviewed digital images of all radiographs.

Results

Between September 2002 and August 2003, 777 patients met the case definition. The measured minimum incidence was 177/100 000 but the estimated incidence was as high as 580/100 000 with full adjustment for incomplete chest radiography and access to health care. Seventy-two (9%) patients died and 28% were known to be HIV positive. Fifteen (2%) patients had pneumonia twice during the year. The average cost of hospitalization for an episode of pneumonia ranged from US$490.80 to $628.60.

Conclusions

Pneumonia is a significant and costly public health problem in Thailand. This surveillance system allows precise assessment and monitoring of radiologically confirmed pneumonia and lays the groundwork for the introduction of new vaccines against pneumonia pathogens.

Session 1.3: health protection and disease prevention: a critical review of experience

This is a summary of the presentations and discussion of Health Protection and Disease Prevention of the Conference, Health Aspects of the Tsunami Disaster in Asia, convened by the World Health Organization (WHO) in Phuket, Thailand, 04-06 May 2005. The topics discussed included issues related health protection and disease prevention as pertaining to the responses to the damage created by the Tsunami. It is presented in the following major sections: (1) key questions; (2) national perspectives; (3) an international perspective; (4) laboratory aspects in disease surveillance; and (5) partnership.

Dengue Virus (DV) enhancing antibody activity in preillness plasma does not predict subsequent disease severity or viremia in secondary DV infection

BACKGROUND

Dengue hemorrhagic fever, the most severe form of dengue illness, is associated with secondary dengue virus (DV) infection. Preexisting nonneutralizing antibodies to DV that enhance the infection of Fc gamma receptor-bearing cells have been implicated in DV pathogenesis.

METHODS

We conducted a prospective cohort study in Thai schoolchildren. Enhancing activity (EA) was measured as the percentage of DV-infected K562 cells, and viral titer (infected K562 cell supernatants) was measured in preillness plasma samples from children who subsequently had secondary DV2 or DV3 infection.

RESULTS

Plaque-reduction neutralizing titers to the child's own DV2 or DV3 isolate were detected in 23 of 32 and 8 of 27 of the preillness plasma samples, and EA was detected to a low-passage Thai DV2 or DV3 in 31 of 32 and 26 of 27, respectively, of the samples. EA in undiluted preillness plasma did not correlate with subsequent disease severity or peak viremia levels in either secondary DV2 or DV3 infections.

CONCLUSIONS

Preillness plasma enhances DV infection of K562 cells even in the presence of detectable neutralizing antibodies in LLC-MK2 cells. However, levels of preillness plasma EA of DV infection in K562 cells did not correlate with the clinical severity or viral burden of secondary DV infection.

Prospective population-based incidence of Haemophilus influenzae type b meningitis in Thailand

There are limited prospective data for Haemophilus influenzae type b (Hib) disease in Asia, where some countries are considering vaccine introduction. A prospective population-based study was conducted to measure the incidence of Hib meningitis in children in two northern provinces of Thailand. Children <5 years with symptoms consistent with bacterial meningitis were enrolled in the study if inclusion criteria were met. The study enrolled 598 children with clinical meningitis, 76% of whom received lumbar puncture. The rate of probable bacterial meningitis was 26.6/100,000 children <5 years per year. There were four cases of laboratory confirmed Hib meningitis (rate 3.8/100,000 children <5 years per year). These findings suggest a relatively low incidence of Hib meningitis. However, additional data from studies of pneumonia are needed to define the Hib disease burden in Thailand.

Comparative evaluation of a combined DTP-HB vaccine in the EPI in Chiangrai Province, Thailand

Combined vaccines have been advocated as an efficient method of paediatric vaccine delivery. This study examined the performance and cost implications for the use of combined DTP-HB vaccine in the Thai immunisation program. Separate DTP and HB and then combined DTP-HB vaccines were used in the infant immunisation program in Chiangrai Province during a 4-year period. DTP vaccination coverage was maintained with the combined vaccine and HB coverage was improved (95.7% for DTP-HB1, 95.2% for DTP-HB2 and 93.8% for DTP-HB3). Seroconversion rates for anti-HBs rose from a baseline of 88.4 to 94.8% with use of the combined vaccine. Seroconversion rates for anti-D (97.5%) and anti-P (89.6%) were higher in the separate vaccine regimen. Although this study was not able to demonstrate that DTP-HB vaccine was more cost saving than the vaccines given separately as baseline vaccine coverage was already high, in settings where coverage rates are much lower the increased cost of combined vaccines may be more justifiable.

Spatial and temporal circulation of dengue virus serotypes: a prospective study of primary school children in Kamphaeng Phet, Thailand

Dengue virus occurs as four distinct serotypes, each of which causes epidemics throughout the tropical and subtropical regions of the world. Few studies have examined co-circulation of multiple dengue virus serotypes in a well-defined cohort population over time and their capacity to produce severe dengue disease. In this paper, the authors report the details and findings of the first 3 years (1998-2000) of an ongoing prospective study of dengue virus transmission and disease severity in a cohort of children in northern Thailand. A total of 108 dengue virus isolates were obtained from 167 acute dengue virus infections; 23% were DEN-1, 35% were DEN-2, 41% were DEN-3, and 1% were DEN-4. Despite the proximity of the schools, there was marked spatial and temporal clustering of transmission of each dengue serotype. Serotype-specific antibody levels prior to the dengue transmission season were not predictive of the incidence of dengue virus infections or the predominant serotype transmitted at individual schools. All dengue serotypes produced severe dengue illness, although DEN-3 produced more severe symptoms than the other dengue serotypes. The authors' findings emphasize the complexity of dengue serotype-specific virus transmission and severe dengue disease and have important implications for dengue control and vaccine development.

Epidemiology of inapparent and symptomatic acute dengue virus infection: a prospective study of primary school children in Kamphaeng Phet, Thailand

Dengue viruses are a major cause of morbidity in tropical and subtropical regions of the world. Knowledge about the epidemiology and host determinants of inapparent and severe dengue virus infections is limited. In this paper, the authors report findings from the first 3 years of a prospective study of dengue virus transmission and disease severity conducted in a cohort of 2,119 elementary school children in northern Thailand. A total of 717,106 person-school days were observed from 1998 to 2000. The incidence of inapparent and of symptomatic dengue virus infection was 4.3% and 3.6% in 1998, 3.2% and 3.3% in 1999, and 1.4% and 0.8% in 2000, respectively. Symptomatic dengue virus infection was responsible for 3.2%, 7.1%, and 1.1% of acute-illness school absences in 1998, 1999, and 2000, respectively. The early symptom complex of acute dengue virus infection is protean and difficult to distinguish from other causes of febrile childhood illnesses. The authors' results illustrate the spatial and temporal diversity of dengue virus infection and the burden of dengue disease in schoolchildren in Thailand. Their findings increase understanding of dengue virus transmission and disease severity in a well-defined cohort population and offer a study design in which to test the efficacy of potential dengue vaccines.

Dengue-specific T cell responses in peripheral blood mononuclear cells obtained prior to secondary dengue virus infections in Thai schoolchildren

Children who experience secondary dengue virus (DV) infections are at increased risk for dengue hemorrhagic fever. To study the effect of preexisting T cell responses to DV on the severity of secondary virus infection, peripheral blood mononuclear cells (PBMC) from 10 subsequently hospitalized and 12 nonhospitalized Thai schoolchildren were stimulated with inactivated dengue antigens, and proliferation of interferon (IFN)-gamma or tumor necrosis factor (TNF)-alpha responses of the preinfection PBMC were measured. Proliferation responses were observed in 11 subjects, and IFN-gamma responses were seen in 12 subjects, 6 of whom showed broad serotype cross-reactive IFN-gamma responses. TNF-alpha responses were detected exclusively in 4 hospitalized subjects. Four PBMC samples that showed neither proliferation nor cytokine responses to any dengue antigen were from nonhospitalized subjects. This study, thought to be the first to investigate T cell responses to DV in preinfection PBMC, suggests that the pattern of preexisting T cell responses influences the risk for severe disease.

Environmental and travel factors related to leptospirosis in Thailand

To identify potential environmental and travel factors related to leptospirosis, we conducted an unmatched case controlled study and household assessment of cases and controls in Nakhon Ratchasima province (north-eastern, Thailand) from August to December, 1998. Fifty-six cases and 145 controls were included in the study. Cases were hospitalized patients who had been diagnosed with leptospirosis and tested positive for anti-leptospiral IgM antibody using the Panbio ELISA (Panbio Inc, Brisbane, Australia). Controls were the neighbors of cases who had tested negative. Standardized questionnaires and household assessments were used to collect information on demographics, number of animals kept, evidence of rats in the home, presence of rat food inside the home, road characteristics, awareness of leptospirosis disease, environment, and travel history. Multivariant, unconditional logistic regression demonstrated that travel on potholed roads was independently associated with leptospirosis infection (OR 5.0; 95%CI 1.2-20.2) and traveling by car was a protective factor (OR 0.2; 95%CI 0.06-0.9).

Impact of hepatitis B immunisation as part of the EPI

Since 1992, hepatitis B vaccine has been an integrated part of Thailand's expanded programme on immunisation (EPI). Based on the data from five representative provinces, we have evaluated its impact on the countrywide prevalence of HBV infection and carrier rate. The population studied comprised 400-488 healthy and immuno-competent, subjects per area. The subjects' ages ranged from 6 months to 18 years. We examined their sera for viral hepatitis markers using commercially available test kits and established the coverage rate of hepatitis B vaccination after its inclusion into the EPI to be 71.2-94.3%. The number of individuals undergoing the complete course of vaccinations had increased four-fold. Consequently, only 0.7% of the children born after the implementation of this the novel EPI strategy were HBV carriers.

Persistence of antibodies to the surface antigen of the hepatitis B virus (anti-HBs) in children subjected to the Expanded Programme on Immunization (EPI), including hepatitis-B vaccine, in Thailand

Will hepatitis-B vaccine administered at birth, and at 2 and 6 months of age, as an integral part of Thailand's Expanded Programme on Immunization, provide long-term protection? In an attempt to answer this question, residents of five provinces (representing five distinct geographical areas of Thailand) who were aged 1-10 years and had received this course of vaccination were enrolled on a serological study. Each was tested, with ELISA, for the surface antigen of hepatitis B (HBsAg) and for antibodies against this antigen (anti-HBs) or against the core antigen (anti-HBc). Over all age-groups, the prevalences of HBsAg, anti-HBs and anti-HBc were 0.67%, 71.4% and 5.5%, respectively. Although the prevalence of anti-HBs decreased with age, it remained at 56%-65% among those aged 6-10 years. Between 2% and 17% of the subjects aged 1-9 years had high titres of anti-HBs. Based on these results, an additional booster, still a controversial issue, does not appear to be required in order to prevent infection with hepatitis B virus and thus permit the eventual eradication of chronic carriage and its fatal sequelae in Thailand.

Integration of hepatitis B vaccination into the expanded programme on immunization in Chonburi and Chiangmai provinces, Thailand

Hepatitis B (HB) immunization was introduced as part of the expanded programme on immunization (EPI) in two provinces in Thailand and evaluated over a four year period. Three doses of HB vaccine were offered to 60,980 newborns at birth, 2 and 6 months of age. The overall coverage for complete HB immunization was 90.4%. Serosurveys of randomly selected children under the age of 5 years were undertaken before and at the end of the project. Levels of HBsAg positivity were reduced by 85%, and there was a corresponding 70% increase in protective immunity. These findings demonstrate that HB immunization can be successfully integrated into EPI without adverse effect on coverage rates of other antigens, and results in a marked reduction in the rate of chronic carriage of HB virus in preschool age children.