Viral aetiology of central nervous system infections in adults admitted to a tertiary referral hospital in southern Vietnam over 12 years.

Background: Central nervous system (CNS) infections are important diseases in both children and adults worldwide. The spectrum of infections is broad, encompassing bacterial/aseptic meningitis and encephalitis. Viruses are regarded as the most common causes of encephalitis and aseptic meningitis.

Changes in the hemagglutinin of H5N1 viruses during human infection--influence on receptor binding.

As avian influenza A(H5N1) viruses continue to circulate in Asia and Africa, global concerns of an imminent pandemic persist. Recent experimental studies suggest that efficient transmission between humans of current H5N1 viruses only requires a few genetic changes. An essential step is alteration of the virus hemagglutinin from preferential binding to avian receptors for the recognition of human receptors present in the upper airway.

Viral etiologies of acute respiratory infections among hospitalized Vietnamese children in Ho Chi Minh City, 2004-2008.

Background: The dominant viral etiologies responsible for acute respiratory infections (ARIs) are poorly understood, particularly among hospitalized children in resource-limited tropical countries where morbidity and mortality caused by ARIs are highest. Improved etiological insight is needed to improve clinical management and prevention.

Objectives: We conducted a three-year prospective descriptive study of severe respiratory illness among children from 2 months to 13 years of age within the largest referral hospital for infectious diseases in southern Vietnam.

Random PCR and ultracentrifugation increases sensitivity and throughput of VIDISCA for screening of pathogens in clinical specimens.

Introduction: Virus discovery based on cDNA-AFLP (VIDISCA) is a sequence-independent virus discovery method that was recently developed and successfully used to characterize unknown viruses in cell cultures. Its applicability, however, is limited by its low sensitivity.

Methodology: We evaluated whether the introduction of prior amplification of target sequences by random PCR (rPCR) increases the sensitivity of this method to improve its use on clinical specimens.

Viral etiology of encephalitis in children in southern Vietnam: results of a one-year prospective descriptive study.

Background: Acute encephalitis is an important and severe disease in children in Vietnam. However, little is known about the etiology while such knowledge is essential for optimal prevention and treatment. To identify viral causes of encephalitis, in 2004 we conducted a one-year descriptive study at Children's Hospital Number One, a referral hospital for children in southern Vietnam including Ho Chi Minh City.

Kinetics of neutralizing antibodies in patients naturally infected by H5N1 virus.

Background: Little is known about the kinetics of anti-H5 neutralizing antibodies in naturally H5N1-infected patients with severe clinical illness or asymptomatic infection.

Methods: Using H5N1 microneutralisation (MN) and H5-pseudotype particle-based microneutralisation assays (H5pp) we analyzed sera sequentially obtained from 11 severely ill patients diagnosed by RT-PCR (follow-up range 1-139 weeks of disease onset) and 31 asymptomatically infected individuals detected in a sero-epidemiological study after exposure to H5N1 virus (follow-up range: 1-2 month-11 months after exposure).

Results: Of 44 sera from 11 patients with H5N1 disease, 70% tested positive by MN (antibody titre > or = 80) after 2 weeks and 100% were positive by 3 weeks after disease onset.

Early pandemic influenza (2009 H1N1) in Ho Chi Minh City, Vietnam: a clinical virological and epidemiological analysis.

Background: To date, little is known about the initial spread and response to the 2009 pandemic of novel influenza A ("2009 H1N1") in tropical countries. Here, we analyse the early progression of the epidemic from 26 May 2009 until the establishment of community transmission in the second half of July 2009 in Ho Chi Minh City (HCMC), Vietnam. In addition, we present detailed systematic viral clearance data on 292 isolated and treated patients and the first three cases of selection of resistant virus during treatment in Vietnam.

A real-time RT-PCR for detection of clade 1 and 2 H5N1 influenza A virus using locked nucleic acid (LNA) TaqMan probes.

Background: The emergence and co-circulation of two different clades (clade 1 and 2) of H5N1 influenza viruses in Vietnam necessitates the availability of a diagnostic assay that can detect both variants.

Results: We developed a single real-time RT-PCR assay for detection of both clades of H5N1 viruses, directly from clinical specimens, using locked nucleic acid TaqMan probes. Primers and probe used in this assay were designed based on a highly conserved region in the HA gene of H5N1 viruses.

Me Tri virus: a Semliki Forest virus strain from Vietnam?

Me Tri virus (MTV) is a member of the Semliki Forest virus (SFV) complex in the genus Alphavirus, first isolated from Culex tritaeniorhynchus mosquitoes in Vietnam in 1971 and described as a newly recognized alphavirus, based on antigenic characterization. However, based on a partial nucleotide sequence of the E1 envelope glycoprotein gene, it has recently been argued that MTV may represent a variant of SFV rather than a separate species. To enable definitive classification, we determined the complete genome sequence of MTV from original virus stock.

A sensitive retroviral pseudotype assay for influenza H5N1-neutralizing antibodies.

Background: The World Health Organisation (WHO) recommended the development of simple, safe, sensitive and specific neutralization assays for avian influenza antibodies. We have used retroviral pseudotypes bearing influenza H5 hemagglutinin (HA) as safe, surrogate viruses for influenza neutralization assays which can be carried out at Biosafety Level 2.

Results: Using our assay, sera from patients who had recovered from infection with influenza H5N1, and sera from animals experimentally immunized or infected with H5 tested positive for the presence of neutralizing antibodies to H5N1.

Fatal outcome of human influenza A (H5N1) is associated with high viral load and hypercytokinemia.

Avian influenza A (H5N1) viruses cause severe disease in humans, but the basis for their virulence remains unclear. In vitro and animal studies indicate that high and disseminated viral replication is important for disease pathogenesis. Laboratory experiments suggest that virus-induced cytokine dysregulation may contribute to disease severity.

Oseltamivir resistance during treatment of influenza A (H5N1) infection.

Influenza A (H5N1) virus with an amino acid substitution in neuraminidase conferring high-level resistance to oseltamivir was isolated from two of eight Vietnamese patients during oseltamivir treatment. Both patients died of influenza A (H5N1) virus infection, despite early initiation of treatment in one patient. Surviving patients had rapid declines in the viral load to undetectable levels during treatment.

Fatal avian influenza A (H5N1) in a child presenting with diarrhea followed by coma.

In southern Vietnam, a four-year-old boy presented with severe diarrhea, followed by seizures, coma, and death. The cerebrospinal fluid contained 1 white cell per cubic millimeter, normal glucose levels, and increased levels of protein (0.81 g per liter).