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Chikungunya virus (CHIKV) is recognized but rarely considered as a cause of central nervous system infection in endemic areas. A total of 244 patients with acute meningoencephalitis in Indonesia were retrospectively tested to identify whether any CHIKV infection was associated with neurological manifestations, especially in provinces known for CHIKV endemicity. Cerebrospinal fluid (CSF) and blood specimens were tested using CHIKV-specific real-time reverse transcription polymerase chain reaction and IgM ELISA, alongside a panel of neurotropic viruses. We report four cases of suspected or confirmed CHIKV-associated neurological disease, including CHIKV RNA detection in CSF of one patient and in acute serum of another, and CHIKV IgM in CSF of three patients and in serum of a fourth. In conclusion, CHIKV should be considered as a cause of neurologic disease in endemic areas and especially during outbreaks, in addition to the more common arboviral diseases such as dengue and Japanese encephalitis viruses.

The ongoing COVID-19 pandemic remained a major public health concern despite a large-scale deployment of vaccines. One of the vaccines is CoronaVac, an inactivated vaccine. The efficacy of the vaccine was estimated at 50.7–83.5% in clinical trials. However, the real-world efficacy often differed. This study described CoronaVac post-vaccination reactogenicity and immunogenicity. Serum was collected on days 0, 28, 56 and 84 from participants who received CoronaVac in March–May 2021. Anti-SARS-CoV-2 Spike receptor binding domain was measured using an Elecsys® quantitative assay. Participants were interviewed for adverse events (AEs) one week after vaccination. Reported AEs were fatigue, fever, runny nose, headache, muscle pain, pain at injection site, and paresthesia. Females reported more incidents than males. However, the frequency was similar between immunologically naïve and pre-immune participants. In the naïve group, the antibody titer was 61.7 ± 84.2 U/mL (mean ± SD) on day 28 and increased to 99.3 ± 91.9 U/mL on day 56. The titer peaked on day 56 across all age groups, but a reduction of 18.0–26.3% was observed on day 84. A titer-boosting effect was observed in pre-immune participants with a baseline titer of 139.0 ± 101.0 U/mL, which increased to 206.7 ± 77.4 U/mL on day 28, and remained steady until day 84. Hence, CoronaVac elicited an antibody response in naïve and pre-immune participants, with mild AEs.

The presence of Zika virus (ZIKV) in Indonesia has been recognized since the 1970s, but its transmission dynamics there have been poorly understood. To understand more fully the geographic distribution and burden of ZIKV infection, we performed retrospective serological tests on specimens collected from asymptomatic children age 5 to 9 years old living at 30 sites in 14 provinces. Of 870 serum samples tested, 9.2% were found to be positive for anti-ZIKV antibodies, as confirmed by plaque reduction neutralization assays. This was the same overall prevalence reported previously for 1- to 4-year-old children collected at the same sites at the same time. Together with geographic differences in seroprevalence between the age groups, these data suggest that, although ZIKV might be endemic in Indonesia, its occurrence has been focal and episodic.

Zika virus (ZIKV) has recently been confirmed as endemic in Indonesia, but no congenital anomalies (CA) related to ZIKV infection have been reported. We performed molecular and serological testing for ZIKV and other flaviviruses on cord serum and urine samples collected in October 2016 to April 2017 during a prospective, cross-sectional study of neonates in Jakarta, Indonesia. Of a total of 429 neonates, 53 had CA, including 14 with microcephaly. These 53, and 113 neonate controls without evidence of CA, were tested by ZIKV-specific real-time reverse transcription polymerase chain reaction (RT-PCR), pan-flavivirus RT-PCR, anti-ZIKV and anti-DENV IgM ELISA, and plaque reduction neutralization test. There was no evidence of ZIKV infection among neonates in either the CA or non-CA cohorts, except in three cases with low titers of anti-ZIKV neutralizing antibodies. Further routine evaluation throughout Indonesia of pregnant women and their newborns for exposure to ZIKV should be a high priority for determining risk.

Funder: US-CDC, Background: Chikungunya virus (CHIKV) is an important emerging and re-emerging public health problem worldwide. In Indonesia, where the virus is endemic, epidemiological information from outside of the main islands of Java and Bali is limited. Methodology/Principal Findings: Four hundred and seventy nine acutely febrile patients presenting between September 2017–2019 were recruited from three city hospitals situated in Ambon, Maluku; Banjarmasin, Kalimantan; and Batam, Batam Island as part of a multi-site observational study. CHIKV RNA was detected in a single serum sample while a separate sample was IgM positive. IgG seroprevalence was also low across all three sites, ranging from 1.4–3.2%. The single RT-PCR positive sample from this study and 24 archived samples collected during other recent outbreaks throughout Indonesia were subjected to complete coding region sequencing to assess the genetic diversity of Indonesian strains. Phylogenetic analysis revealed all to be of a single clade, which was distinct from CHIKV strains recently reported from neighbouring regions including the Philippines and the Pacific Islands. Conclusions/Significance: Chikungunya virus strains from recent outbreaks across Indonesia all belong to a single clade. However, low-level seroprevalence and molecular detection of CHIKV across the three study sites appears to contrast with the generally high seroprevalences that have been reported for non-outbreak settings in Java and Bali, and may account for the relative lack of CHIKV epidemiological data from other regions of Indonesia.

The people of Indonesia have been afflicted by dengue, a mosquito-borne viral disease, for over 5 decades. The country is the world's largest archipelago with diverse geographic, climatic, and demographic conditions that may impact the dynamics of disease transmissions. A dengue epidemiology study was launched by us to compare and understand the dynamics of dengue and other arboviral diseases in three cities representing western, central, and eastern Indonesia, namely, Batam, Banjarmasin, and Ambon, respectively. A total of 732 febrile patients were recruited with dengue-like illness during September 2017–2019 and an analysis of their demographic, clinical, and virological features was performed. The seasonal patterns of dengue-like illness were found to be different in the three regions. Among all patients, 271 (37.0%) were virologically confirmed dengue, while 152 (20.8%) patients were diagnosed with probable dengue, giving a total number of 423 (57.8%) dengue patients. Patients' age and clinical manifestations also differed between cities. Mostly, mild dengue fever was observed in Batam, while more severe cases were prominent in Ambon. While all dengue virus (DENV) serotypes were detected, distinct serotypes dominated in different locations: DENV-1 in Batam and Ambon, and DENV-3 in Banjarmasin. We also assessed the diagnostic features in the study sites, which revealed different patterns of diagnostic agreements, particularly in Ambon. To detect the possibility of infection with other arboviruses, further testing on 461 DENV RT-PCR-negative samples was performed using pan-flavivirus and -alphavirus RT-PCRs; however, only one chikungunya infection was detected in Ambon. A diverse dengue epidemiology in western, central, and eastern Indonesia was observed, which is likely to be influenced by local geographic, climatic, and demographic conditions, as well as differences in the quality of healthcare providers and facilities. Our study adds a new understanding on dengue epidemiology in Indonesia.

Background Rickettsia felis has recently emerged worldwide as a cause of human illness. Typically causing mild, undifferentiated fever, it has been implicated in several cases of non-fatal neurological disease in Mexico and Sweden. Its distribution and pathogenicity in Southeast Asia is poorly understood. Methodology/Principal findings We retroactively tested cerebrospinal fluid (CSF) or sera from 64 adult patients admitted to hospital in North Sulawesi, Indonesia with acute neurological disease. Rickettsia felis DNA was identified in the CSF of two fatal cases of meningoencephalitis using multi-locus sequence typing semi-nested PCR followed by Sanger sequencing. DNA from both cases had 100% sequence homologies to the R. felis reference strain URRWXCal2 for the 17-kDa and ompB genes, and 99.91% to gltA. Conclusion/Significance The identification of R. felis in the CSF of two fatal cases of meningoencephalitis in Indonesia suggests the distribution and pathogenicity of this emerging vector-borne bacteria might be greater than generally recognized. Typically Rickettsia are susceptible to the tetracyclines and greater knowledge of R. felis endemicity in Indonesia should lead to better management of some acute neurological cases., Author summary Rickettsia felis is a flea-borne bacteria that has recently emerged worldwide as a cause of disease. Little is known about its distribution or details of transmission but typically it has been described as causing mild, self-limiting, febrile illness. It has, however, been incriminated in Mexico and Sweden of causing acute neurological disease. We report from North Sulawesi, Indonesia evidence that R. felis caused or contributed to the death of two adult men admitted to hospital with progressive meningoencephalitis. One case was a farmer and the other was an itinerant urban salesman. DNA unique to R. felis was identified in the patients’ cerebrospinal fluid using Sanger sequencing techniques. No other potential pathogens were found. These appear to be the first possible cases of fatal R. felis reported. Because rickettsial infections can usually be quickly, cheaply, and effectively treated with doxycycline and related tetracylines, it is important for clinicians in the region to consider using these antibiotics to treat suspect cases presumptively.

Background We explored the outcome of convalescent plasma (CP) treatment in patients with moderate and severe coronavirus disease 2019 (COVID-19) and investigated variables for the design of further trials in Indonesia. Methods Hospitalised patients with moderate (n = 5) and severe (n = 5) COVID-19 were recruited and transfused with CP from donors who recovered from mild (n = 5), moderate (n = 5), or severe (n = 1) COVID-19. Neutralising antibodies (NAbs) to the virus were measured at the end of the study using a surrogate virus neutralisation test as an alternative to the plaque reduction assay. Clinical improvement was assessed based on the modified World Health Organization Research and Development Blueprint six-point scale, Brixia Chest-X-Ray scoring, and laboratory parameters. The study was registered at ClinicalTrials.gov (NCT04407208). Findings CP transfusion in three doses of 3 mL/kg of recipient body weight at 2-day intervals was well tolerated. Good clinical improvement was achieved in all patients with moderate disease and in two patients with severe disease. Most patients at baseline had detectable NAbs with median inhibition rates comparable to those of the donors (90·91% vs. 86·31%; p = 0·379). This could be due to the unavailability of pre-donation NAb testing and postponed CP administration that required communal consent. Interpretation This study highlights the safety of CP therapy. Although improvements were observed, we could not conclude that the outcomes were solely due to CP treatment. Further randomised controlled trials that cover different disease stages with pre-donation NAb measurements using locally applicable strategies are warranted. Funding The study was supported by PT Bio Farma, Indonesia.

Central nervous system involvement of dengue virus is increasingly reported from endemic areas. This study describes the clinical characteristics and laboratory features of a pediatric patient enrolled in a central nervous system illness study conducted in 2017–2018 to identify viral and bacterial etiologies in Indonesian children. Dengue diagnostics including molecular and serological testing were performed on an encephalitis patient who presented with both classical dengue and neurological clinical symptoms. Dengue virus serotype 1 RNA was detected in both cerebrospinal fluid and serum by serotype-specific reverse transcription polymerase chain reaction, and the E gene was successfully sequenced. Anti-dengue virus immunoglobulin M was detected in both admission and discharge sera, whereas anti-dengue virus immunoglobulin G was identified only in the discharge serum. This study describes the central nervous system complications in a case with dengue virus infection in West Java, Indonesia, and highlights the potential for dengue virus serotype 1, a serotype rarely associated with neurotropism, to cause encephalitis.

Platelets are understood to assist host innate immune responses against infection, although direct evidence of this function in any human disease, including malaria, is unknown. Here we characterized platelet–erythrocyte interactions by microscopy and flow cytometry in patients with malaria naturally infected with Plasmodium falciparum, Plasmodium vivax, Plasmodium malariae, or Plasmodium knowlesi. Blood samples from 376 participants were collected from malaria-endemic areas of Papua, Indonesia, and Sabah, Malaysia. Platelets were observed binding directly with and killing intraerythrocytic parasites of each of the Plasmodium species studied, particularly mature stages, and was greatest in P vivax patients. Platelets preferentially bound to the infected more than to the uninfected erythrocytes in the bloodstream. Analysis of intraerythrocytic parasites indicated the frequent occurrence of platelet-associated parasite killing, characterized by the intraerythrocytic accumulation of platelet factor-4 and terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick-end labeling of parasite nuclei (PF4+TUNEL+ parasites). These PF4+TUNEL+ parasites were not associated with measures of systemic platelet activation. Importantly, patient platelet counts, infected erythrocyte-platelet complexes, and platelet-associated parasite killing correlated inversely with patient parasite loads. These relationships, taken together with the frequency of platelet-associated parasite killing observed among the different patients and Plasmodium species, suggest that platelets may control the growth of between 5% and 60% of circulating parasites. Platelet–erythrocyte complexes made up a major proportion of the total platelet pool in patients with malaria and may therefore contribute considerably to malarial thrombocytopenia. Parasite killing was demonstrated to be platelet factor-4-mediated in P knowlesi culture. Collectively, our results indicate that platelets directly contribute to innate control of Plasmodium infection in human malaria.

Platelets are understood to assist host innate immune responses against infection, although direct evidence of this function in any human disease, including malaria, is unknown. Here we characterized platelet-erythrocyte interactions by microscopy and flow cytometry in patients with malaria naturally infected with