Low Zika Virus Seroprevalence in Vientiane, Laos, 2003–2015

International audienceZika virus (ZIKV) has been presumed to be endemic in Southeast Asia (SEA), with a low rate of human infections. Although the first ZIKV evidence was obtained in the 1950s through serosurveys, the first laboratory-confirmed case was only detected in 2010 in Cambodia. The epidemiology of ZIKV in SEA remains uncertain because of the scarcity of available data. From 2016, subsequent to the large outbreaks in the Pacific and Latin America, several Asian countries started reporting increasing numbers of confirmed ZIKV patients, but no global epidemiological assessment is available to date. Here, with the aim of providing information on ZIKV circulation and population immunity, we conducted a seroprevalence study among blood donors in Vientiane, Laos. Sera from 359 asymptomatic consenting adult donors in 2003-2004 and 687 in 2015 were screened for anti-ZIKV IgG using NS1 ELISA assay (Euroimmun, Luebeck, Germany). Positive and equivocal samples were confirmed for anti-ZIKV-neutralizing antibodies by virus neutralization tests. Our findings suggest that ZIKV has been circulating in Vientiane over at least the last decade. Zika virus seroprevalence observed in the studied blood donors was low, 4.5% in 2003-2004 with an increase in 2015 to 9.9% (P = 0.002), possibly reflecting the increase of ZIKV incident cases reported over this period. We did not observe any significant difference in seroprevalence according to gender. With a low herd immunity in the Vientiane population, ZIKV represents a risk for future large-scale outbreaks. Implementation of a nationwide ZIKV surveillance network and epidemiological studies throughout the country is needed

Viral RNA Degradation Makes Urine a Challenging Specimen for Detection of Japanese Encephalitis Virus in Patients With Suspected CNS Infection: JEV RNA Not Detected in Urine of Suspected Central Nervous System Infections.

International audienceBackground: Japanese encephalitis virus (JEV) is a leading cause of central nervous system (CNS) infections in Asia and results in significant morbidity and mortality. JEV RNA is rarely detected in serum or cerebrospinal fluid (CSF), and diagnosis of JEV infection is usually based on serological tests that are frequently difficult to interpret. Unlike serum or CSF, urine is relatively easy to obtain, but, to date, there has been minimal work on the feasibility of testing urine for JEV RNA.Methods: We investigated the use of lysis buffer and a Microsep device to optimize urine storage for detection of JEV RNA by reverse transcription real-time polymerase chain reaction (RT-qPCR). The best of the studied methods was then evaluated in consecutive patients admitted to the hospital with suspected CNS infections in Laos.Results: We demonstrated degradation of JEV RNA in urine after even short storage periods at 4°C or -80°C. Although there was no advantage in using a Microsep concentration device alone, immediate addition of lysis buffer to fresh urine improved the detection of JEV RNA at the limit of detection.Conclusions: In 2 studies of 41 patients with acute encephalitis syndrome, 11 (27%) were positive for JEV IgM in CSF and/or serum, and 2 (4.9%) were JEV RT-qPCR positive from throat swabs. JEV RNA was not detected in any of these patients' urine samples. However, lysis buffer was only used during a prospective study, that is, for only 17/41 (41%) patient urine samples. Our findings suggest a need for larger studies testing urine for JEV RNA, with urine collected at different times from symptom onset, and using lysis buffer, which stabilizes RNA, for storage

Detection of Japanese Encephalitis Virus RNA in Human Throat Samples in Laos – A Pilot study

International audienceJapanese encephalitis virus (JEV) is the most commonly identified cause of acute encephalitis syndrome (AES) in Asia. The WHO recommended test is anti-JEV IgM-antibody-capture-enzyme-linked-immunosorbent-assay (JEV MAC-ELISA). However, data suggest this has low positive predictive value, with false positives related to other Flavivirus infections and vaccination. JEV RT-PCR in cerebrospinal fluid (CSF) and/or serum is highly specific, but is rarely positive; 0–25% of patients that fulfil the WHO definition of JE (clinical Acute Encephalitis Syndrome (AES) and JEV MAC-ELISA positive). Testing other body fluids by JEV RT-qPCR may improve the diagnosis. As a pilot study thirty patients admitted to Mahosot Hospital 2014–2017, recruited to the SouthEast -Asia-Encephalitis study, were tested by JEV MAC-ELISA and two JEV real-time RT-PCR (RT-qPCR) assays (NS2A and NS3). Eleven (36.7%) were JEV MAC-ELISA positive. Available CSF and serum samples of these patients were JEV RT-qPCR negative but 2 (7%) had JEV RNA detected in their throat swabs. JEV RNA was confirmed by re-testing, and sequencing of RT-qPCR products. As the first apparent report of JEV RNA detection in human throat samples, the provides new perspectives on human JEV infection, potentially informing improving JEV detection. We suggest that testing patients' throat swabs for JEV RNA is performed, in combination with molecular and serological CSF and serum investigations, on a larger scale to investigate the epidemiology of the presence of JEV in human throats. Throat swabs are an easy and non-invasive tool that could be rolled out to a wider population to improve knowledge of JEV molecular epidemiology. Evidence continues to implicate Japanese encephalitis virus (JEV) as a major cause of encephalitis in Asia, with recent evidence of possible autochthonous transmission in Africa 1–3. Among the key factors in its persistent role as a public health problem are the limitations of existing diagnostic tests, our understanding of its epidemiology and inadequate implementation of vaccination programmes. The conventional mainstay of JEV encephalitis diagnosis is serology, with serum and cerebrospinal fluid (CSF) anti-JEV IgM antibody capture enzyme-linked immunosorbent assays (JEV MAC-ELISA) recommended by the World Health Organization (WHO) 4. However, there are concerns about the accuracy of JEV MAC-ELISA for diagnosing JEV. Low positive predictive value of JEV MAC-ELISA has been reported 5 , and there are recognised difficulties with false positives related to vaccination and in areas where other Flavivirus infections are endemic 6,7. Diagnosis of JEV by Reverse-Transcription (RT)-PCR is highly specific, and enables improved understanding of the molecular epidemiology of JEV 8. However, JEV RT-PCR testing of CSF and serum samples has low sensitivity , rarely positive in patients at presentation (0–25% that fulfil the WHO definition of Acute Encephaliti

JEV MAC-ELISA results from DCS using CSF-substitutes, 903 filter paper and various protocols for sample spotting.

<p>JEV MAC-ELISA results from DCS using CSF-substitutes, 903 filter paper and various protocols for sample spotting.</p

Anti-JEV IgM ELISA (JEV MAC-ELISA) results of consecutive patient samples comparing Dried Cerebrospinal Fluid Spots (DCS) on filter paper using the pre-cut protocol vs routine neat Cerebrospinal Fluid.

<p>Anti-JEV IgM ELISA (JEV MAC-ELISA) results of consecutive patient samples comparing Dried Cerebrospinal Fluid Spots (DCS) on filter paper using the pre-cut protocol vs routine neat Cerebrospinal Fluid.</p

Study sites: Geographical distribution of four hospitals involved in patient recruitment, in Vientiane (colour map), and with respect to the Lao PDR (grey map).

<p>Study sites: Geographical distribution of four hospitals involved in patient recruitment, in Vientiane (colour map), and with respect to the Lao PDR (grey map).</p

Causes of Fever in Rural Southern Laos

The etiology of fever in rural Lao People’s Democratic Republic (Laos) has remained obscure until recently owing to the lack of laboratory facilities. We conducted a study to determine the causes of fever among 229 patients without malaria in Savannakhet Province, southern Laos; 52% had evidence of at least one diagnosis (45% with single and 7% with apparent multiple infections). Among patients with only one diagnosis, dengue (30.1%) was the most common, followed by leptospirosis (7.0%), Japanese encephalitis virus infection (3.5%), scrub typhus (2.6%), spotted fever group infection (0.9%), unspecified flavivirus infection (0.9%), and murine typhus (0.4%). Herein, we discuss the empirical treatment of fever in relation to these findings

Primers and probes evaluated during the study.

<p>Primers and probes evaluated during the study.</p