Mong How Ooi

Virology, epidemiology, pathogenesis, and control of enterovirus 71

First isolated in California, USA, in 1969, enterovirus 71 (EV71) is a major public health issue across the Asia-Pacific region and beyond. The virus, which is closely related to polioviruses, mostly affects children and causes hand, foot, and mouth disease with neurological and systemic complications. Specific receptors for this virus are found on white blood cells, cells in the respiratory and gastrointestinal tract, and dendritic cells. Being an RNA virus, EV71 lacks a proofreading mechanism and is evolving rapidly, with new outbreaks occurring across Asia in regular cycles, and virus gene subgroups seem to differ in clinical epidemiological properties. The pathogenesis of the severe cardiopulmonary manifestations and the relative contributions of neurogenic pulmonary oedema, cardiac dysfunction, increased vascular permeability, and cytokine storm are controversial. Public health interventions to control outbreaks involve social distancing measures, but their effectiveness has not been fully assessed. Vaccines being developed include inactivated whole-virus, live attenuated, subviral particle, and DNA vaccines.

Clinical features, diagnosis, and management of enterovirus 71

Although poliomyelitis has been mostly eradicated worldwide, large outbreaks of the related enterovirus 71 have been seen in Asia-Pacific countries in the past 10 years. This virus mostly affects children, manifesting as hand, foot, and mouth disease, aseptic meningitis, poliomyelitis-like acute flaccid paralysis, brainstem encephalitis, and other severe systemic disorders, including especially pulmonary oedema and cardiorespiratory collapse. Clinical predictors of severe disease include high temperature and lethargy, and lumbar puncture might reveal pleocytosis. Many diagnostic tests are available, but PCR of throat swabs and vesicle fluid, if available, is among the most efficient. Features of inflammation, particularly in the anterior horns of the spinal cord, the dorsal pons, and the medulla can be clearly seen on MRI. No established antiviral treatment is available. Intravenous immunoglobulin seems to be beneficial in severe disease, perhaps through non-specific anti-inflammatory mechanisms, but has not been tested in any formal trials. Milrinone might be helpful in patients with cardiac dysfunction.

Human Enterovirus 71 Disease in Sarawak, Malaysia: A Prospective Clinical, Virological, and Molecular Epidemiological Study

BACKGROUND Human enterovirus (HEV)-71 causes large outbreaks of hand-foot-and-mouth disease with central nervous system (CNS) complications, but the role of HEV-71 genogroups or dual infection with other viruses in causing severe disease is unclear. METHODS We prospectively studied children with suspected HEV-71 (i.e., hand-foot-and-mouth disease, CNS disease, or both) over 3.5 years, using detailed virological investigation and genogroup analysis of all isolates. RESULTS Seven hundred seventy-three children were recruited, 277 of whom were infected with HEV-71, including 28 who were coinfected with other viruses. Risk factors for CNS disease in HEV-71 included young age, fever, vomiting, mouth ulcers, breathlessness, cold limbs, and poor urine output. Genogroup analysis for the HEV-71-infected patients revealed that 168 were infected with genogroup B4, 68 with C1, and 41 with a newly emerged genogroup, B5. Children with HEV-71 genogroup B4 were less likely to have CNS complications than those with other genogroups (26 [15%] of 168 vs. 30 [28%] of 109; odds ratio [OR], 0.48; 95% confidence interval [CI], 0.26-0.91; P=.0223) and less likely to be part of a family cluster (12 [7%] of 168 vs. 29 [27%] of 109; OR, 0.21; 95% CI, 0.10-0.46; P<.0001); children with HEV-71 genogroup B5 were more likely to be part of a family cluster (OR, 6.26; 95% CI, 2.77-14.18; P<.0001). Children with HEV-71 and coinfected with another enterovirus or adenovirus were no more likely to have CNS disease. CONCLUSIONS Genogroups of HEV-71 may differ with regard to the risk of causing CNS disease and the association with family clusters. Dual infections are common, and all possible causes should be excluded before accepting that the first virus identified is the causal agent.

West Nile encephalitis

Although West Nile encephalitis is yet to spread to the United Kingdom, it is becoming more prevalent in the rest of the world. This article reviews the recent outbreaks and examines the current methods of diagnosis, treatment, and prevention

A cohort study to assess the new WHO Japanese encephalitis surveillance standards

Objective To assess the field-test version of the new WHO Japanese encephalitis (JE) surveillance standards. Methods We applied the clinical case definition of acute encephalitis syndrome (AES), laboratory diagnostic criteria and case classifications to patients with suspected central nervous system (CNS) infections in southern Viet Nam. Findings Of the 380 patients (149 children) recruited with suspected CNS infections, 296 (96 children) met the AES case definition. 54 children were infected with JE virus (JEV), of whom 35 (65%) had AES, giving a sensitivity of 65% (95% CI: 56–73) and specificity of 39% (95% CI: 30–48). Nine adults with JEV presented with AES. 19 JEV-infected children missed by surveillance included 10 with acute flaccid paralysis, two with flaccid hemiparesis and six with meningism only. Altering the case definition to include limb paralysis and meningism improved sensitivity to 89% (95% CI: 83–95), while reducing specificity to 23% (95% CI: 15–30). Six children that did not have AES on admission had reduced consciousness after admission. Cerebrospinal fluid (CSF) analysis diagnosed seven patients negative on serum analysis. Five patients with neurological manifestations of dengue infection had JEV antibodies in serum and would have been misdiagnosed had we not tested for dengue antibodies in parallel. Conclusion Children infected with JEV that presented with acute limb paralysis or neck stiffness only were missed by the surveillance standards, although some of them subsequently became encephalopathic. A footnote in the surveillance standards drawing attention to these presentations would be helpful. An acute CSF sample is more sensitive and specific than an acute serum sample.

Identification and validation of clinical predictors for the risk of neurological involvement in children with hand, foot, and mouth disease in Sarawak

BackgroundHuman enterovirus 71 (HEV71) can cause Hand, foot, and mouth disease (HFMD) with neurological complications, which may rapidly progress to fulminant cardiorespiratory failure, and death. Early recognition of children at risk is the key to reduce acute mortality and morbidity.MethodsWe examined data collected through a prospective clinical study of HFMD conducted between 2000 and 2006 that included 3 distinct outbreaks of HEV71 to identify risk factors associated with neurological involvement in children with HFMD.ResultsTotal duration of fever ≥ 3 days, peak temperature ≥ 38.5°C and history of lethargy were identified as independent risk factors for neurological involvement (evident by CSF pleocytosis) in the analysis of 725 children admitted during the first phase of the study. When they were validated in the second phase of the study, two or more (≥ 2) risk factors were present in 162 (65%) of 250 children with CSF pleocytosis compared with 56 (30%) of 186 children with no CSF pleocytosis (OR 4.27, 95% CI2.79–6.56, p < 0.0001). The usefulness of the three risk factors in identifying children with CSF pleocytosis on hospital admission during the second phase of the study was also tested. Peak temperature ≥ 38.5°C and history of lethargy had the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of 28%(48/174), 89%(125/140), 76%(48/63) and 50%(125/251), respectively in predicting CSF pleocytosis in children that were seen within the first 2 days of febrile illness. For those presented on the 3rd or later day of febrile illness, the sensitivity, specificity, PPV and NPV of ≥ 2 risk factors predictive of CSF pleocytosis were 75%(57/76), 59%(27/46), 75%(57/76) and 59%(27/46), respectively.ConclusionThree readily elicited clinical risk factors were identified to help detect children at risk of neurological involvement. These risk factors may serve as a guide to clinicians to decide the need for hospitalization and further investigation, including cerebrospinal fluid examination, and close monitoring for disease progression in children with HFMD.

The Epidemiology, Clinical Features, and Long-Term Prognosis of Japanese Encephalitis in Central Sarawak, Malaysia, 1997–2005

BACKGROUND Japanese encephalitis is a major public health problem in Asia. However, there is little data on the long-term outcome of Japanese encephalitis survivors. METHODS We prospectively evaluated children with serologically confirmed Japanese encephalitis over an 8.3-year period. The patients were assessed and their outcomes were graded with a functional outcome score at hospital discharge and at follow-up appointments. We examined how patient outcome at hospital discharge compared with that at long-term follow-up visits, when changes in outcome occurred, and the prognostic indicators of the eventual outcome. RESULTS One hundred and eighteen patients were recruited into the study, and 10 (8%) died during the acute phase of illness. At hospital discharge, 44 (41%) of the 108 patients who survived had apparent full recovery; 3 (3%) had mild, 28 (26%) had moderate, and 33 (31%) had severe neurological sequelae. Eighty six of the 108 patients were followed up for a median duration of 52.9 months (range, 0.9-114.9 months). During follow-up, 31 patients experienced improvement, but 15 patients experienced deterioration in their outcome grade. In most cases, assessment during the first 3-6 months after hospital discharge was predictive of the long-term outcome. More than one-half of the patients continued to experience neuropsychological sequelae and behavioral disorders. A combination of poor perfusion, Glasgow coma score < or =8, and > or =2 witnessed seizures predicted a poor long-term outcome with 65% sensitivity and 92% specificity. CONCLUSIONS Neurological assessment of Japanese encephalitis survivors at hospital discharge does not predict long-term outcome. Seizures and shock are treatable risk factors for a poor outcome at hospital discharge and at long-term follow-up visits.

Evaluation of Different Clinical Sample Types in Diagnosis of Human Enterovirus 71-Associated Hand-Foot-and-Mouth Disease

ABSTRACT Human enterovirus 71 and coxsackievirus A16 are important causes of hand-foot-and-mouth disease (HFMD). Like other enteroviruses, they can be isolated from a range of sterile and nonsterile sites, but which clinical sample, or combination of samples, is the most useful for laboratory diagnosis of HFMD is not clear. We attempted virus culture for 2,916 samples from 628 of 725 children with HFMD studied over a 3 1/2-year period, which included two large outbreaks. Overall, throat swabs were the single most useful specimen, being positive for any enterovirus for 288 (49%) of 592 patients with a full set of samples. Vesicle swabs were positive for 169 (48%) of 333 patients with vesicles, the yield being greater if two or more vesicles were swabbed. The combination of throat plus vesicle swabs enabled the identification of virus for 224 (67%) of the 333 patients with vesicles; for this patient group, just 27 (8%) extra patients were diagnosed when rectal and ulcer swabs were added. Of 259 patients without vesicles, use of the combination of throat plus rectal swab identified virus for 138 (53%). For 60 patients, virus was isolated from both vesicle and rectal swabs, but for 12 (20%) of these, the isolates differed. Such discordance occurred for just 11 (10%) of 112 patients with virus isolated from vesicle and throat swabs. During large HFMD outbreaks, we suggest collecting swabs from the throat plus one other site: vesicles, if these are present (at least two should be swabbed), or the rectum if there are no vesicles. Vesicle swabs give a high diagnostic yield, with the added advantage of being from a sterile site.

Dengue virus serotype 2 from a sylvatic lineage isolated from a patient with dengue hemorrhagic fever.

Dengue viruses circulate in both human and sylvatic cycles. Although dengue viruses (DENV) infecting humans can cause major epidemics and severe disease, relatively little is known about the epidemiology and etiology of sylvatic dengue viruses. A 20-year-old male developed dengue hemorrhagic fever (DHF) with thrombocytopenia (12,000/ul) and a raised hematocrit (29.5% above baseline) in January 2008 in Malaysia. Dengue virus serotype 2 was isolated from his blood on day 4 of fever. A phylogenetic analysis of the complete genome sequence revealed that this virus was a member of a sylvatic lineage of DENV-2 and most closely related to a virus isolated from a sentinel monkey in Malaysia in 1970. This is the first identification of a sylvatic DENV circulating in Asia since 1975.

Molecular phylogeny of modern coxsackievirus A16

Summary.A phylogenetic analysis of VP1 and VP4 nucleotide sequences of 52 recent CVA16 strains demonstrated two distinct CVA16 genogroups, A and B, with the prototype strain being the only member of genogroup A. CVA16 G-10, the prototype strain, showed a nucleotide difference of 27.7–30.2% and 19.9–25.2% in VP1 and VP4, respectively, in relation to other CVA16 strains, which formed two separate lineages in genogroup B with nucleotide variation of less than 13.4% and less than 16.3% in VP1 and VP4, respectively. Lineage 1 strains circulating before 2000 were later displaced by lineage 2 strains.