A prospective study was carried out to evaluate the sensitivity of dengue NS1 antigen-capture ELISA in comparison with dengue virus isolation, conventional RT-PCR and real-time RT-PCR for laboratory confirmation of acute dengue based on single-acute serum samples. Four primary healthcare centres were involved to recruit patients with clinical diagnosis of dengue illness. Patient's demographic, epidemiological and clinical information were collected on a standardized data entry form and 5 ml of venous blood was collected upon consent. In the laboratory, six types of laboratory tests were performed on each of the collected acute serum sample. Of the 558 acute serum samples collected from 558 patients with clinical diagnosis of dengue from mid-August 2006 to March 2009, 174 serum samples were tested positive by the dengue NS1 antigen-capture ELISA, 77 by virus isolation, 92 by RT-PCR and 112 by real-time RT-PCR. A total of 190 serum samples were tested positive by either one or a combination of the four methods whereas, only 59 serum samples were tested positive by all four methods. Thus, based on single-acute serum samples, 190 of the 558 patients (34.1%) were laboratory-confirmed acute dengue. The overall test sensitivity was 91.6%, 40.5%, 48.4% and 58.9% for dengue NS1 antigen-capture ELISA, virus isolation, conventional RT-PCR and real-time RT-PCR respectively. Statistically, dengue NS1 antigen-capture ELISA was the most sensitive and virus isolation was the least sensitive test for the laboratory confirmation of acute dengue based on single-acute serum specimens. Real-time RT-PCR was significantly more sensitive than the conventional RT-PCR.
Bats are increasingly being recognized as important reservoir hosts for a large number of viruses, some of them can be highly virulent when they infect human and livestock animals. Among the new bat zoonotic viruses discovered in recent years, several reoviruses (respiratory enteric orphan viruses) were found to be able to cause acute respiratory infections in humans, which included Melaka and Kampar viruses discovered in Malaysia, all of them belong to the genus Orthoreovirus, family Reoviridae. In this report, we describe the isolation of a highly related virus from an adult patient who suffered acute respiratory illness in Malaysia. Although there was no direct evidence of bat origin, epidemiological study indicated the potential exposure of the patient to bats before the onset of disease. The current study further demonstrates that spillover events of different strains of related orthoreoviruses from bats to humans are occurring on a regular basis, which calls for more intensive and systematic surveillances to fully assess the true public health impact of these newly discovered bat-borne zoonotic reoviruses.
Classical dengue fever is characterized by the clinical features of fever, headache, severe myalgia and occasionally rash, which can also be caused by a number of other viral and bacterial infections. Five hundred and fifty eight patients who fulfilled the criteria of clinical diagnosis of acute dengue from 4 government outpatient polyclinics were recruited in this prospective field study. Of the 558 patients, 190 patients were categorized as acute dengue fever, 86 as recent dengue and 282 as non-dengue febrile illnesses based on the results of a number of laboratory tests. Epidemiological features of febrile patients showed that the mean age of patients in the dengue fever group was significantly younger in comparison with patients in the non-dengue group. There was no significant difference between the two groups with respect to gender but there was significant ethnic difference with foreign workers representing a higher proportion in the dengue fever group. Patients with acute dengue fever were more likely to have patient-reported rash and a history of dengue in family or neighbourhood but less likely to have respiratory symptoms, sore-throat and jaundice in comparison to patients with non-dengue febrile illnesses. As with patients with dengue fever, patients in the recent dengue group were more likely to have history of patient-reported rash and a history of dengue contact and less likely to have respiratory symptoms in comparison to patients with non-dengue febrile illnesses. In contrast to patients with dengue fever, patients in the recent dengue group were more likely to have abdominal pain and jaundice in comparison to non-dengue febrile patients. The finding strongly suggests that a proportion of patients in the recent dengue group may actually represent a subset of patients with acute dengue fever at the late stage of illness.
Study site: Klinik Kesihatan Seksyen 7, Shah Alam; Klinik Kesihatan Kelana Jaya, Petaling Jaya; Klinik Kesihatan Sg. Buloh; Klinik Kesihatan Jinjang, Selangor, Kuala Lumpur, Malaysia