Kouichi Morita’s research while affiliated with Kenya Medical Research Institute and other places

Background Rotavirus, norovirus, adenovirus (type 40/41) and astrovirus are the most significant viral etiological agents of acute gastroenteritis in young children globally. Kenya introduced the rotavirus vaccine into her National Immunization Program in July 2014, which has led to a significant decline in the prevalence of rotavirus. We sought to assess the impact of rotavirus vaccination on the epidemiological trends of other diarrhea-associated enteric viruses across different regions in Kenya. Methodology Using conventional and multiplex RT-PCR, we analyzed a total of 716 fecal samples for adenovirus, astrovirus and norovirus from children aged below 5 years presenting with acute gastroenteritis but tested negative for rotavirus at Mbita Sub-County Referral Hospital in Western Kenya and Kiambu County Referral Hospital in Central Kenya before (2011–2013) and after (2019–2020) rotavirus vaccine introduction. Results Following the rotavirus vaccine introduction, there was no significant difference in norovirus and astrovirus prevalence post-vaccine introduction in both Central (norovirus- 5.4% vs 5.9%; astrovirus- 2% vs 2.4%) and Western Kenya (norovirus- 2% vs 3%; astrovirus 3.3% vs 5.9%). Although the prevalence of adenovirus increased substantially in Western Kenya (9% vs 12.4%), there was a significant decrease in adenovirus in Central Kenya (17%, vs 6%, p = 0.007). Before the introduction of the rotavirus vaccine, a large proportion of adenovirus cases occurred at 6–8 months in Central Kenya and 12–23 months in Western Kenya, while norovirus prevalence was highest at 12–23 months in Central and 3–5 months in Western Kenya. Astrovirus infections in Central Kenya were predominantly among children aged 12–23 months, both before and after the vaccine. Following vaccine introduction, a large proportion of adenovirus cases occurred among children aged 12–23 months in both regions. Norovirus peaked at 12–23 months in Central Kenya and showed dual peaks at 3–5 and 9–11 months in Western Kenya. Astrovirus infections in Western Kenya shifted from peaks at 6–8 and 24–59 months pre-vaccine to 9–11 months post-vaccine. Conclusion Our data demonstrate the burden and changing epidemiology of enteric viruses in Western and Central Kenya and underscores the need for continued monitoring to guide the design and implementation of appropriate public health interventions.

Background Chikungunya virus (CHIKV) is a mosquito-borne alphavirus and an emerging global health threat. Most research on CHIKV in Malaysia has primarily focused on Peninsular Malaysia, with limited data on its distribution in the endemic regions of Borneo, particularly Sabah. This study aimed to determine the prevalence of CHIKV infection in Sabah, Malaysia. Methods A total of 130 serum samples, comprising 74 from febrile patients and 56 healthy individuals were collected between 2017 and 2018. Subsequently, 188 serum samples were obtained from febrile patients in Sabah, Malaysia during 2019–2020. All samples underwent quantitative real-time reverse transcription polymerase chain reaction (RT-qPCR) for the detection of the CHIKV genome. Additionally, serological tests were conducted to identify anti-CHIKV IgM and IgG antibodies. Serologically positive samples were further validated using neutralization assays to confirm the presence of CHIKV-specific antibodies. Results In 2017–2018, 16 out of 130 samples (12.3%) tested positive for recent CHIKV infections based on CHIKV RT-qPCR or anti-CHIKV IgM results, while in 2019–2020, 7 out of 188 samples (3.7%) showed recent infections. Among the 16 recent CHIKV-positive cases in 2017–2018, four were asymptomatic individuals. In 2017–2018, 24 (18.4%) individuals tested positive for anti-CHIKV IgG, with 15 (11.5%) showing positive neutralization test results. In 2019–2020, 20 (10.6%) febrile patients were seropositive for anti-CHIKV IgG, with 17 (9.0%) showing CHIKV neutralization positivity. The CHIKV infection rate in Sabah was higher during 2017–2018 compared to 2019–2020. Conclusions To the best of our knowledge, this is the first report confirming the presence of CHIKV in both patients and healthy individuals in Sabah using RT-qPCR and neutralization tests. Although the likelihood of transmission from asymptomatic individuals is low, they still present a considerable public health risk. Our results indicate that both basic scientists and clinicians should consider CHIKV when diagnosing febrile patients, and policymakers should put in place effective surveillance and control measures.

Dengue is the most common arboviral infection, causing significant morbidity and mortality. Currently, more than half of the world’s population is at risk, particularly in tropical and subtropical regions of Asia, with the virus now spreading to new areas in Europe and the Americas, a silent epidemic in Africa. Current efforts including dengue surveillance, partially effective vaccines, innovative vector control strategies, and a better understanding of the disease pathogenesis are significant. We argue that the future of dengue prevention requires more than just the advancements made so far. The development of a highly effective vaccine, paired with enhanced public health strategies, is essential for long-term control and reducing the global impact of dengue.

Due to the similar symptoms with dengue fever (DF) and dengue hemorrhagic fever (DHF), Chikungunya (CHIK) virus infections were diagnosed as DF or DHF. In this study, we examined more than 300 serum samples collected from dengue-suspected patients in San Lazaro Hospital and St. Luke's Medical Center. Reverse transcriptase-polymerase chain reaction (RT-PCR) and antigen sandwich enzyme-linked immunosorbent assay (ELISA) were applied for CHIK virus detection. IgM-indirect immunofluorescent antibody test (IgM-IFA), IgM capture ELISA, and IgG indirect ELISA were applied for detection of serological evidence of CHIK virus infection. Although we could not detect any Chikungunya virus by RT-PCR, 4.1% of the confirmed samples showed high titer for Chikungunya virus by antigen sandwich ELISA. By IgM-IFA, 15.3% were positive for CHIK virus. Thirteen point seven percent showed positive for CHIK virus by IgM-capture ELISA. Eighteen point five percent showed positive for CHIK virus by IgG indirect ELISA.

Background Bali, one of the world's most popular tourist destinations, is hyper‐endemic to dengue, an acute febrile illness caused by infection with dengue virus (DENV). Outbreaks of dengue occur annually with worrisome rates of morbidity and mortality. Despite this, comprehensive and continuous virus surveillance is yet to be established. We conducted DENV serotype and genotype surveillance in Bali to monitor viral transmission dynamics. Methods We enrolled febrile patients with dengue clinical symptoms in hospitals in Denpasar, Bali. Clinical evaluations and laboratory assessments were conducted, and blood samples were collected. DENV serotypes were determined using RT‐PCR, and genotyping was performed by sequencing the envelope protein gene and the complete genomes. Subsequently, phylogenetic analyses were conducted to analyse the recent data alongside retrospective sequence data. Results A total of 62 and 66 dengue patients were recruited during 2018–2020 and 2022, and from these, we obtained DENV serotype data for 49 and 48 individuals, respectively. Among the DENV analysed, the most prevalent serotype in 2018–2020 was DENV‐1 (30%) and shifted to DENV‐3 (57.6%) in 2022. When compared to data from the last 10 years, serotype shifting was clearly observed. We sequenced the genomes of 60 isolates and observed the presence of multiple virus lineages and the replacement of Genotype IV of DENV‐1 with Genotype I. The Cosmopolitan, Genotype I and Genotype II remained the predominant genotypes for DENV‐2, DENV‐3 and DENV‐4, respectively. Conclusion We reveal that DENV serotype predominance in Bali has been shifting in the past 10 years. While genotype replacement occurred, continuous circulation of local endemic viruses was responsible for the annual outbreak of dengue. These findings indicate the genetic diversity and dynamic nature of DENV circulating in Bali. Routine virus surveillance is important to understand the cyclical patterns of DENV serotypes that is useful to predict the future outbreaks.

Background Myanmar is one of the countries in Southeast Asia where serious dengue outbreaks occur and Yangon is among the regions with the highest number of cases in the country. Many infections including dengue are common in Yangon during the rainy season, and co-infections may also occur. Adults are more likely than children to experience co-infections of dengue and other diseases. Although pediatric dengue has been studied in Yangon for decades, research on adult dengue is scant. Therefore, this study compared the clinical and virological characteristics of pediatric and adult dengue cases in Yangon. Methods This cross-sectional study was conducted at Insein General Hospital in Yangon, Myanmar, from June to September 2022. We recruited 221 suspected dengue patients (134 children and 87 adults), with or without other diseases, and tested their dengue serological markers using a serological method and their dengue virus (DENV) serotypes using conventional RT-PCR. Chi-squared and Fisher’s exact tests were conducted to assess significance. Results The dengue non-structural protein-1 antigen (NS1Ag) positivity was 37% in children and 32% in adults. DENV serotypes were identified in 80% of NS1Ag-positive patients. Among NS1Ag-positive cases, the DENV-1 serotype predominated (67%), followed by DENV-2 (17%), DENV-3 (9%), DENV-4 (5%), and mixed DENV-1 and DENV-2 (2%) serotypes. Shock was observed in 14% of children and 3% of adults. Anti-dengue IgG antibody positivity was positively correlated with dengue shock. Three pediatric dengue cases (6%) also had other infections including bronchiolitis, ear infection, and diarrhea. Seven adult dengue cases (25%) also had other diseases including advanced HIV infection, severe pneumonia, tonsillitis, thyroid disease, cholecystitis, drug poisoning, and thalassemia. Conclusion The serotype distribution and clinical presentations of pediatric and adult dengue cases were not significantly different, but adults were more likely to have dengue together with other diseases than children. This study provides information for the better management of febrile children and adults in hospital settings and provides a foundation for nationwide epidemiological studies on dengue serotypes and modifications of the national guidelines for dengue management in Myanmar.

We report a human case of severe fever with thrombocytopenia syndrome virus infection transmitted by a tick, confirmed by viral identification. Haemaphysalis aborensis, a tick species not native to Japan that has been observed to transmit the virus to humans, is now recognized as a potential vector of this virus in Japan.

Rapid progression to fatal expanded dengue syndrome is unusual, presenting a challenge for clinical management. We present a case of a 32-year-old female with atypical dengue manifestations who underwent extensive evaluation at a Kathmandu infectious disease hospital, including vital signs assessment, clinical scoring, and routine and advanced laboratory analyses. Severe abdominal pain, disorientation, and abnormal hemodynamics with multi-organ involvement were noted with a secondary dengue virus (DENV) infection. Co-infection of DENV-1 and DENV-3, exhibiting high viral loads, was observed, marking the first fatal case of its kind in Nepal. Despite intensive care management, the patient’s condition rapidly deteriorated, leading to fatal expanded dengue syndrome within four days of a hospital visit. This poses a serious challenge to clinicians. Heightened vigilance from the onset of DENV infection is imperative, regardless of serotypes or viral load levels. Predictive markers for early detection and management strategies are urgently needed to achieve the WHO's goal of zero dengue-related deaths by 2030.