Somsak Thamthitiwat

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.

The burden of hospitalized lower respiratory tract infection due to respiratory syncytial virus in rural Thailand.

Background We describe the epidemiology of hospitalized RSV infections for all age groups from population-based surveillance in two rural provinces in Thailand. Methods From September 1, 2003 through December 31, 2007, we enrolled hospitalized patients with acute lower respiratory tract illness, who had a chest radiograph ordered by the physician, from all hospitals in SaKaeo and Nakhom Phanom Provinces. We tested nasopharyngeal specimens for RSV with reverse transcriptase polymerase chain reaction (RT-PCR) assays and paired-sera from a subset of patients with IgG enzyme immunoassay. Rates were adjusted for enrollment. Results Among 11,097 enrolled patients, 987 (8.9%) had RSV infection. Rates of hospitalized RSV infection overall (and radiographically-confirmed pneumonia) were highest among children aged <1 year: 1,067/100,000 (534/100,000 radiographically-confirmed pneumonia) and 1–4 year: 403/100,000 (222/100,000), but low among enrolled adults aged ≥65 years: 42/100,000. Age <1 year (adjusted odds ratio [aOR] u200a=u200a13.2, 95% confidence interval [CI] 7.7, 22.5) and 1–4 year (aORu200a=u200a8.3, 95% CI 5.0, 13.9) were independent predictors of hospitalized RSV infection. Conclusions The incidence of hospitalized RSV lower respiratory tract illness among children <5 years was high in rural Thailand. Efforts to prevent RSV infection could substantially reduce the pneumonia burden in children aged <5 years.

Antibiotic Use in Thailand: Quantifying Impact on Blood Culture Yield and Estimates of Pneumococcal Bacteremia Incidence

No studies have quantified the impact of pre-culture antibiotic use on the recovery of individual blood-borne pathogens or on population-level incidence estimates for Streptococcus pneumoniae. We conducted bloodstream infection surveillance in Thailand during November 2005–June 2008. Pre-culture antibiotic use was assessed by reported use and by serum antimicrobial activity. Of 35,639 patient blood cultures, 27% had reported pre-culture antibiotic use and 24% (of 24,538 tested) had serum antimicrobial activity. Pathogen isolation was half as common in patients with versus without antibiotic use; S. pneumoniae isolation was 4- to 9-fold less common (0.09% versus 0.37% by reported antibiotic use; 0.05% versus 0.45% by serum antimicrobial activity, P < 0.01). Pre-culture antibiotic use by serum antimicrobial activity reduced pneumococcal bacteremia incidence by 32% overall and 39% in children < 5 years of age. Our findings highlight the limitations of culture-based detection methods to estimate invasive pneumococcal disease incidence in settings where pre-culture antibiotic use is common.

Incidence and Etiology of Acute Lower Respiratory Tract Infections in Hospitalized Children Younger Than 5 Years in Rural Thailand

Background: Pneumonia remains a leading cause of under-five morbidity and mortality globally. Comprehensive incidence, epidemiologic and etiologic data are needed to update prevention and control strategies. Methods: We conducted active, population-based surveillance for hospitalized cases of acute lower respiratory tract infections (ALRI) among children <5 years of age in rural Thailand. ALRI cases were systematically sampled for an etiology study that tested nasopharyngeal specimens by polymerase chain reaction; children without ALRI were enrolled as controls from outpatient clinics. Results: We identified 28,543 hospitalized ALRI cases from 2005 to 2010. Among the 49% with chest radiographs, 63% had findings consistent with pneumonia as identified by 2 study radiologists. The hospitalized ALRI incidence rate was 5772 per 100,000 child-years (95% confidence interval: 5707, 5837) and was higher in boys versus girls (incidence rate ratio 1.38, 95% confidence interval: 1.35–1.41) and in children 6–23 months of age versus other age groups (incidence rate ratio 1.76, 95% confidence interval: 1.69–1.84). Viruses most commonly detected in ALRI cases were respiratory syncytial virus (19.5%), rhinoviruses (18.7%), bocavirus (12.8%) and influenza viruses (8%). Compared with controls, ALRI cases were more likely to test positive for respiratory syncytial virus, influenza, adenovirus, human metapneumovirus and parainfluenza viruses 1 and 3 (P ⩽ 0.01 for all). Bloodstream infections, most commonly Streptococcus pneumoniae and nontyphoidal Salmonella, accounted for 1.8% of cases. Conclusions: Our findings underscore the high burden of hospitalization for ALRI and the importance of viral pathogens among children in Thailand. Interventions targeting viral pathogens coupled with improved diagnostic approaches, especially for bacteria, are critical for better understanding of ALRI etiology, prevention and control.

Survey of Legionella Species Found in Thai Soil

Members of the Gram-negative genus Legionella are typically found in freshwater environments, with the exception of L. longbeachae, which is present in composts and potting mixes. When contaminated aerosols are inhaled, legionellosis may result, typically as either the more serious pneumonia Legionnaires disease or the less severe flu-like illness Pontiac fever. It is presumed that all species of the genus Legionella are capable of causing disease in humans. As a followup to a prior clinical study of legionellosis in rural Thailand, indigenous soil samples were collected proximal to cases homes and workplaces and tested for the presence of legionellae by culture. We obtained 115 isolates from 22/39 soil samples and used sequence-based methods to identify 12 known species of Legionella represented by 87 isolates.

Infective Endocarditis in Northeastern Thailand

Despite rigorous diagnostic testing, the cause of infective endocarditis was identified for just 60 (45.5%) of 132 patients admitted to hospitals in Khon Kaen, Thailand, during January 2010–July 2012. Most pathogens identified were Viridans streptococci and zoonotic bacteria species, as found in other resource-limited countries where underlying rheumatic heart disease is common.

Incidence of Bacteremic Melioidosis in Eastern and Northeastern Thailand

Burkholderia pseudomallei, the causative agent of melioidosis, is endemic in northeastern Thailand. Population-based disease burden estimates are lacking and limited data on melioidosis exist from other regions of the country. Using active, population-based surveillance, we measured the incidence of bacteremic melioidosis in the provinces of Sa Kaeo (eastern Thailand) and Nakhon Phanom (northeastern Thailand) during 2006-2008. The average annual incidence in Sa Kaeo and Nakhon Phanom per 100,000 persons was 4.9 (95% confidence interval [CI] = 3.9-6.1) and 14.9 (95% CI = 13.3-16.6). The respective population mortality rates were 1.9 (95% CI = 1.3-2.8) and 4.4 (95% CI = 3.6-5.3) per 100,000. The case-fatality proportion was 36% among those with known outcome. Our findings document a high incidence and case fatality proportion of bacteremic melioidosis in Thailand, including a region not traditionally considered highly endemic, and have potential implications for clinical management and health policy.

The first reported cases of Q fever endocarditis in Thailand

We describe the first two reported cases of Q fever endocarditis in Thailand. Both patients were male, had pre-existing heart valve damage and had contact with cattle. Heightened awareness of Q fever could improve diagnosis and case management and stimulate efforts to identify risk factors and preventive measures.

Concurrent influenza virus infection and tuberculosis in patients hospitalized with respiratory illness in Thailand

Thailand, where influenza viruses circulate year‐round, is one of 22 WHO‐designated high‐burden countries for tuberculosis (TB). Surveillance for hospitalized respiratory illness between 2003 and 2011 revealed 23 (<1% of 7180 tested) with concurrent influenza and TB. Only two persons were previously known to have TB suggesting that acute respiratory illness may bring patients to medical attention and lead to TB diagnosis. Influenza/TB was not associated with higher disease severity or mortality.

Economic burden of bacteremic melioidosis in eastern and northeastern, Thailand.

Melioidosis is among the most common causes of septicemia in Thailand, but data on economic burden are limited. We describe the economic impact of bacteremic melioidosis hospitalizations in two Thailand provinces during 2006-2008. Costs are presented in US dollars (