Climate change and its impact on infectious diseases in Asia.

ABSTRACT: Climate change, particularly increasing temperature, changes in rainfall, extreme weather events and changes in vector ecology, impacts the transmission of many climate-sensitive infectious diseases. Asia is the world's most populous, rapidly evolving and diverse continent, and it is already experiencing the effects of climate change. Climate change intersects with population, sociodemographic and geographical factors, amplifying the public health impact of infectious diseases and potentially widening existing disparities. In this narrative review, we outline the evidence of the impact of climate change on infectious diseases of importance in Asia, including vector-borne diseases, food- and water-borne diseases, antimicrobial resistance and other infectious diseases. We also highlight the imperative need for strategic intersectoral collaboration at the national and global levels and for the health sector to implement adaptation and mitigation measures, including responsibility for its own greenhouse gas emissions.

DYNAMIC cohort study evaluating metabolic predictors of influenza vaccine immune response in older adults.

Immunosenescence (age-related immune dysfunction) and inflamm-aging contribute to suboptimal immune responses in older adults to standard-dose influenza vaccines, which may be exacerbated in those with metabolic co-morbidities. We sought to investigate metabolic factors/predictors of influenza vaccine immune response in an older adult (age ≥65 years) cohort in Singapore, where influenza typically circulates year-round. The primary outcome for the DYNAMIC prospective cohort study was haemagglutination-inhibition titer (HAI) response to each of the trivalent inactivated influenza vaccine strains at day 28 (D28) compared to baseline (D0), as assessed by seroconversion and D28/D0 log2 HAI fold rise. Baseline blood samples were tested for total Vitamin D (25-(OH) D) levels. We enrolled 234 participants in June-Dec 2017. Two hundred twenty completed all study visits. The median age was 71 [IQR 68-75] years, 67 (30.5%) had diabetes mellitus (DM), and the median BMI was 24.9 [IQR 22.2-27.8] kg/m2. Median baseline totals 25-(OH) D was 29 [IQR: 21-29] ng/ml. Age, DM, obesity, and baseline 25-(OH) D were not associated with HAI fold rise in multivariable analysis. More recent prior influenza vaccination and higher baseline HAI titers were associated with lower HAI fold rise for influenza A/HK/H3N2. Physical activity was associated with a higher HAI fold rise for influenza A/HK/H3N2 in a dose-response relationship (p-test for trend = 0.015). Older adults with well-controlled metabolic co-morbidities retain HAI response to the influenza vaccine, and physical activity had a beneficial effect on immune response, particularly for influenza A/HK/H3N2.

Why Climate Action Is Global Health Action.

The impacts of climate change on global health and populations are far-reaching, yet they disproportionately affect vulnerable groups, thereby exacerbating disparities. As humanity reckons with the emergency of climate change, our global health community needs to contend with our own contributions to greenhouse gas emissions. We know that transformation is possible and that climate action is the antidote to the existential challenge. As a global health community, we have an immense opportunity, responsibility, and commitment to lead, support, inspire, and empower climate action, research, and innovation that align deeply with our mission and core values.

Association of systemic vitamin D on the course of dengue virus infection in adults: a single-centre dengue cohort study at a large institution in Singapore.

INTRODUCTION: Host immune responses may impact dengue severity in adults. Vitamin D has multiple immunomodulatory effects on innate and adaptive immunity. METHODS: We evaluated the association between systemic 25-hydroxyvitamin D [25-(OH) D] and dengue disease severity in adults. We measured plasma for total 25-(OH) D levels with an electrochemiluminescence immunoassay using stored samples from participants with laboratory confirmed dengue who were prospectively enrolled in 2012-2016 at our institution. RESULTS: 80 participants (median age 43 years) were enrolled. Six participants had severe dengue based on the World Health Organisation (WHO) 1997 criteria (i.e. dengue haemorrhagic fever/dengue shock syndrome) and another six had severe dengue based on the WHO 2009 criteria. Median 25-(OH) D at acute phase of dengue was 6.175 µg/L (interquartile range 3.82-8.21; range 3.00-15.29) in all participants. 25-(OH) D showed inverse linear trend with severe dengue manifestations based on the WHO 2009 criteria (aRR 0.72; 95% confidence interval 0.57-0.91; p < 0.01) after adjustment for age, gender and ethnicity. CONCLUSION: Limited studies have evaluated the role of systemic 25-(OH) D on dengue severity. Our study found low systemic 25-(OH) D was associated with increased dengue disease severity, particularly for severe bleeding that was not explained by thrombocytopenia. Further studies investigating the underlying immune mechanisms and effects on the vascular endothelium are needed.

Antibody Response of Heterologous vs Homologous Messenger RNA Vaccine Boosters Against the Severe Acute Respiratory Syndrome Coronavirus 2 Omicron Variant: Interim Results from the PRIBIVAC Study, a Randomized Clinical Trial.

BACKGROUND: Waning antibody levels post-vaccination and the emergence of variants of concern (VOCs) capable of evading protective immunity have raised the need for booster vaccinations. However, which combination of coronavirus disease 2019 (COVID-19) vaccines offers the strongest immune response against the Omicron variant is unknown. METHODS: This randomized, participant-blinded, controlled trial assessed the reactogenicity and immunogenicity of different COVID-19 vaccine booster combinations. A total of 100 BNT162b2-vaccinated individuals were enrolled and randomized 1:1 to either homologous (BNT162b2 + BNT162b2 + BNT162b2; "BBB") or heterologous messenger RNA (mRNA) (BNT162b2 + BNT162b2 + mRNA-1273; "BBM") booster vaccine. The primary end point was the level of neutralizing antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) wild-type and VOCs at day 28. RESULTS: A total of 51 participants were allocated to BBB and 49 to BBM; 50 and 48, respectively, were analyzed for safety and immunogenicity outcomes. At day 28 post-boost, mean SARS-CoV-2 spike antibody titers were lower with BBB (22 382 IU/mL; 95% confidence interval [CI], 18 210 to 27 517) vs BBM (29 751 IU/mL; 95% CI, 25 281 to 35 011; P = .034) as was the median level of neutralizing antibodies: BBB 99.0% (interquartile range [IQR], 97.9% to 99.3%) vs BBM 99.3% (IQR, 98.8% to 99.5%; P = .021). On subgroup analysis, significant higher mean spike antibody titer, median surrogate neutralizing antibody level against all VOCs, and live Omicron neutralization titer were observed only in older adults receiving BBM. Both vaccines were well tolerated. CONCLUSIONS: Heterologous mRNA-1273 booster vaccination compared with homologous BNT123b2 induced a stronger neutralizing response against the Omicron variant in older individuals. CLINICAL TRIALS REGISTRATION: NCT05142319.

Vaccine-associated Rubella - a report of two cases and a review of the literature.

We report the clinical characteristics of two adult patients, presenting with a typical erythematous rash consistent with rubella disease after MMR vaccination. Both patients had an uncomplicated clinical course and recovered uneventfully. One patient was confirmed to have vaccine-associated rubella via sequencing of virus isolated in viral culture. The other patient had a pharyngeal swab positive for rubella virus PCR, with sequencing matching the vaccine strain. There are few reports of clinical disease from rubella vaccine-strains in the literature. Previous authors have reported severe disseminated vaccine-associated rubella in both immunodeficient and immunocompetent patients. Further study is required to ascertain the incidence, risk factors, and clinical characteristics of this condition; as well as investigate the extent of horizontal transmission to guide infection control recommendations.

SARS-CoV-2 seroprevalence and transmission risk factors among high-risk close contacts: a retrospective cohort study.

BACKGROUND: The proportion of asymptomatic carriers and transmission risk factors of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) among household and non-household contacts remains unclear. In Singapore, extensive contact tracing by the Ministry of Health for every diagnosed COVID-19 case, and legally enforced quarantine and intensive health surveillance of close contacts provided a rare opportunity to determine asymptomatic attack rates and SARS-CoV-2 transmission risk factors among community close contacts of patients with COVID-19. METHODS: This retrospective cohort study involved all close contacts of confirmed COVID-19 cases in Singapore, identified between Jan 23 and April 3, 2020. Household contacts were defined as individuals who shared a residence with the index COVID-19 case. Non-household close contacts were defined as those who had contact for at least 30 min within 2 m of the index case. All patients with COVID-19 in Singapore received inpatient treatment, with access restricted to health-care staff. All close contacts were quarantined for 14 days with thrice-daily symptom monitoring via telephone. Symptomatic contacts underwent PCR testing for SARS-CoV-2. Secondary clinical attack rates were derived from the prevalence of PCR-confirmed SARS-CoV-2 among close contacts. Consenting contacts underwent serology testing and detailed exposure risk assessment. Bayesian modelling was used to estimate the prevalence of missed diagnoses and asymptomatic SARS-CoV-2-positive cases. Univariable and multivariable logistic regression models were used to determine SARS-CoV-2 transmission risk factors. FINDINGS: Between Jan 23 and April 3, 2020, 7770 close contacts (1863 household contacts, 2319 work contacts, and 3588 social contacts) linked to 1114 PCR-confirmed index cases were identified. Symptom-based PCR testing detected 188 COVID-19 cases, and 7582 close contacts completed quarantine without a positive SARS-CoV-2 PCR test. Among 7518 (96·8%) of the 7770 close contacts with complete data, the secondary clinical attack rate was 5·9% (95% CI 4·9-7·1) for 1779 household contacts, 1·3% (0·9-1·9) for 2231 work contacts, and 1·3% (1·0-1·7) for 3508 social contacts. Bayesian analysis of serology and symptom data obtained from 1150 close contacts (524 household contacts, 207 work contacts, and 419 social contacts) estimated that a symptom-based PCR-testing strategy missed 62% (95% credible interval 55-69) of COVID-19 diagnoses, and 36% (27-45) of individuals with SARS-CoV-2 infection were asymptomatic. Sharing a bedroom (multivariable odds ratio [OR] 5·38 [95% CI 1·82-15·84]; p=0·0023) and being spoken to by an index case for 30 min or longer (7·86 [3·86-16·02]; p<0·0001) were associated with SARS-CoV-2 transmission among household contacts. Among non-household contacts, exposure to more than one case (multivariable OR 3·92 [95% CI 2·07-7·40], p<0·0001), being spoken to by an index case for 30 min or longer (2·67 [1·21-5·88]; p=0·015), and sharing a vehicle with an index case (3·07 [1·55-6·08]; p=0·0013) were associated with SARS-CoV-2 transmission. Among both household and non-household contacts, indirect contact, meal sharing, and lavatory co-usage were not independently associated with SARS-CoV-2 transmission. INTERPRETATION: Targeted community measures should include physical distancing and minimising verbal interactions. Testing of all household contacts, including asymptomatic individuals, is warranted. FUNDING: Ministry of Health of Singapore, National Research Foundation of Singapore, and National Natural Science Foundation of China.

Pregnancy Outcomes in COVID-19: A Prospective Cohort Study in Singapore.

INTRODUCTION: Pregnant women are reported to be at increased risk of severe coronavirus disease 2019 (COVID-19) due to underlying immunosuppression during pregnancy. However, the clinical course of COVID-19 in pregnancy and risk of vertical and horizontal transmission remain relatively unknown. We aim to describe and evaluate outcomes in pregnant women with COVID-19 in Singapore. METHODS: Prospective observational study of 16 pregnant patients admitted for COVID-19 to 4 tertiary hospitals in Singapore. Outcomes included severe disease, pregnancy loss, and vertical and horizontal transmission. RESULTS: Of the 16 patients, 37.5%, 43.8% and 18.7% were infected in the first, second and third trimesters, respectively. Two gravidas aged ≥35 years (12.5%) developed severe pneumonia; one patient (body mass index 32.9kg/m2) required transfer to intensive care. The median duration of acute infection was 19 days; one patient remained reverse transcription polymerase chain reaction (RT-PCR) positive >11 weeks from diagnosis. There were no maternal mortalities. Five pregnancies produced term live-births while 2 spontaneous miscarriages occurred at 11 and 23 weeks. RT-PCR of breast milk and maternal and neonatal samples taken at birth were negative; placenta and cord histology showed non-specific inflammation; and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific immunoglobulins were elevated in paired maternal and umbilical cord blood (n=5). CONCLUSION: The majority of COVID-19 infected pregnant women had mild disease and only 2 women with risk factors (obesity, older age) had severe infection; this represents a slightly higher incidence than observed in age-matched non-pregnant women. Among the women who delivered, there was no definitive evidence of mother-to-child transmission via breast milk or placenta.

Epidemiology and Relative Severity of Influenza Subtypes in Singapore in the Post-Pandemic Period from 2009 to 2010.

BACKGROUND: After 2009, pandemic influenza A(H1N1) [A(H1N1)pdm09] cocirculated with A(H3N2) and B in Singapore. METHODS: A cohort of 760 participants contributed demographic data and up to 4 blood samples each from October 2009 to September 2010. We compared epidemiology of the 3 subtypes and investigated evidence for heterotypic immunity through multivariable logistic regression using a generalized estimating equation. To examine age-related differences in severity between subtypes, we used LOESS (locally weighted smoothing) plots of hospitalization to infection ratios and explored birth cohort effects referencing the pandemic years (1957; 1968). RESULTS: Having more household members aged 5-19 years and frequent public transport use increased risk of infection, while preexisting antibodies against the same subtype (odds ratio [OR], 0.61; P = .002) and previous influenza infection against heterotypic infections (OR, 0.32; P = .045) were protective. A(H1N1)pdm09 severity peaked in those born around 1957, while A(H3N2) severity was least in the youngest individuals and increased until it surpassed A(H1N1)pdm09 in those born in 1952 or earlier. Further analysis showed that severity of A(H1N1)pdm09 was less than that for A(H3N2) in those born in 1956 or earlier (P = .021) and vice versa for those born in 1968 or later (P < .001), with no difference in those born between 1957 and 1967 (P = .632). CONCLUSIONS: Our findings suggest that childhood exposures had long-term impact on immune responses consistent with the theory of antigenic sin. This, plus observations on short-term cross-protection, have implications for vaccination and influenza epidemic and pandemic mitigation strategies.

Infectious diseases and migrant worker health in Singapore: a receiving country's perspective.

Background: Approximately 1.4 million migrant workers reside in Singapore, presenting unique infectious disease challenges to both migrants and Singapore. Methods: A Pubmed, MEDLINE (Ovid), EBSCO Host (Global Health) and Google Scholar search was performed for both peer, non-peer reviewed articles and reports relevant to migrant health in Singapore, published between 1 January 1989 and 1 September 2016. Additional studies were identified from citations within searched articles. We also reviewed published data and policy documents from the Ministries of Health and Manpower, Singapore. Results: A significant proportion of malaria, enteric fevers, hepatitis A and E and tuberculosis diagnosed in Singapore involve migrant workers. From the 1990-2000 through 2009-11, while malaria and hepatitis A cases have decreased and remain sporadic, enteric fevers and tuberculosis cases have increased, possibly due to greater influx of migrant workers. Hepatitis E numbers remain low but migrant workers account for half of diagnosed cases. In an interplay of immune naivete, work and living conditions, migrants in the construction industry are at higher risk of arboviral infections such as dengue, Zika and chikungunya. Infections such as chikungunya were likely introduced into Singapore by travellers including migrant workers from the Indian subcontinent but autochthonous transmission continued due to the presence of competent mosquito vectors. There is less data regarding sexual health, networks and infections amongst migrant workers, an area which merits further attention. Conclusions: Migrant workers appear to be at higher risk than Singaporeans for specific infectious diseases, probably due to a complex interplay of several factors, including higher disease prevalence in their countries of origin, socio-economic factors, their living conditions in Singapore and financial, language and cultural barriers to healthcare access. Receiving countries need improved surveillance, expansion of preventive measures and decreased barriers to healthcare access for migrant workers.

Vitamin D, leptin and impact on immune response to seasonal influenza A/H1N1 vaccine in older persons.

BACKGROUND: Influenza-related complications are highest in the elderly. Vaccine efficacy is lower due to immunosenescence. Vitamin D's immunomodulatory role was studied in the context of vaccine response. METHODS: We evaluated the effect of baseline 25-(OH) D on vaccine-induced immunological response in a cohort of 159 healthy subjects ages 50-74 in Rochester, MN, who received one dose of seasonal trivalent 2010-2011 influenza vaccine, containing A/California/H1N1- like virus. We examined correlations between 25-(OH) D, leptin, and leptin-related gene SNPs to understand the role of leptin and vitamin D's effects. RESULTS: The median (IQR) baseline for total 25-(OH) D was 44.4 ng/mL (36.6-52.2 ng/mL). No correlation was observed with age. No correlation between 25-(OH) D levels and humoral immune outcomes existed at any timepoint. There was a weak positive correlation between 25-(OH) D levels and change (Day 75-Day 0) in influenza-specific granzyme-B response (r=0.16, p=0.04). We found significant associations between 3 SNPs in the PPARG gene and 25-(OH) D levels (rs1151996, p=0.01; rs1175540, p= 0.02; rs1175544, p=0.03). CONCLUSION: Several SNPs in the PPARG gene were significantly associated with baseline 25-(OH) D levels. Understanding the functional and mechanistic relationships between vitamin D and influenza vaccine-induced immunity could assist in directing new influenza vaccine design.

"Let there be light": the role of vitamin D in the immune response to vaccines.

Vitamin D's non-skeletal actions, including immunomodulatory role, have been increasingly recognized. Of significance, many immune cells are able to synthesize a biologically active form of vitamin D from circulating 25-hydroxyvitamin D with subsequent intracrine actions, and the vitamin D receptor is broadly distributed. In this review, we discuss vitamin D's potent role in innate and adaptive immune responses and published studies evaluating the impact of serum vitamin D, vitamin D gene pathway polymorphisms or empiric vitamin D supplementation on vaccine immunogenicity. We highlight existing knowledge gaps and propose the steps needed to advance the science and answer the question of whether vitamin D may prove valuable as a vaccine adjuvant for certain vaccines against infectious diseases.

The avian influenza vaccine Emerflu. Why did it fail?

Emerflu is an inactivated, split-virion pandemic preparedness vaccine, containing 30 µg of hemagglutinin (HA) and 600 µg of aluminum hydroxide adjuvant. It is administered in two doses, 3 weeks apart. Only moderate immunogenicity was evident from clinical studies with the vaccine in adults, and HA antibody responses were below the criteria established by the EMA and US FDA for licensure. With the exception of Australia, the vaccine remains unlicensed. Further clinical development appears to have been suspended, and newer adjuvants such as MF59 and AS03 have since demonstrated safety and superior immunogenicity with lower HA doses. Emerflu is symbolic of the failure of aluminum salts as an adjuvant for influenza vaccines. Reasons for this failure are unclear, and may reflect problems with the adjuvant-antigen complex or interference in the immune response by heterosubtypic immunity.

Metronidazole- and carbapenem-resistant bacteroides thetaiotaomicron isolated in Rochester, Minnesota, in 2014.

Emerging antimicrobial resistance in members of the Bacteroides fragilis group is a concern in clinical medicine. Although metronidazole and carbapenem resistance have been reported in Bacteroides thetaiotaomicron, a member of the B. fragilis group, they have not, to the best of our knowledge, been reported together in the same B. thetaiotaomicron isolate. Herein, we report isolation of piperacillin-tazobactam-, metronidazole-, clindamycin-, ertapenem-, and meropenem-resistant B. thetaiotaomicron from a patient with postoperative intra-abdominal abscess and empyema. Whole-genome sequencing demonstrated the presence of nimD with at least a portion of IS1169 upstream, a second putative nim gene, two ß-lactamase genes (one of which has not been previously reported), two tetX genes, tetQ, ermF, two cat genes, and a number of efflux pumps. This report highlights emerging antimicrobial resistance in B. thetaiotaomicron and the importance of identification and antimicrobial susceptibility testing of selected anaerobic bacteria.

Non-anti-infective effects of antimicrobials and their clinical applications: a review.

Antimicrobial agents are undoubtedly one of the key advances in the history of modern medicine and infectious diseases, improving the clinical outcomes of infection owing to their inhibitory effects on microbial growth. However, many antimicrobial agents also have biological activities stemming from their interactions with host receptors and effects on host inflammatory responses and other human or bacterial cellular biological pathways. These result in clinical uses of antimicrobial drugs that are distinct from their direct bacteriostatic or bactericidal properties. We reviewed the published literature regarding non-anti-infective therapeutic properties and proposed clinical applications of selected antimicrobials, specifically, macrolides, tetracyclines, sulfonamides, and ketoconazole. The clinical applications reviewed were varied, and we focused on uses that were clinically relevant (in terms of importance and burden of disease) and where published evidence exists. Such uses include chronic inflammatory pulmonary and skin disorders, chronic periodontitis, gastrointestinal dysmotility, rheumatoid arthritis, and cancer. Most of these potential therapeutic uses are not Food and Drug Administration approved. Clinicians need to weigh the use of antimicrobial agents for their non-anti-infective benefits, considering potential adverse effects and long-term effect on microbial resistance.

Clostridium septicum brain abscesses in a premature neonate.

Brain abscesses in neonates are typically caused by Gram-negative organisms. There are no previously described cases caused by Clostridium septicum. We present a case of a premature male infant who developed recurrent episodes of suspected necrotizing enterocolitis followed by brain abscesses, cerebritis and ventriculitis caused by C. septicum.