The incidence of Japanese encephalitis in Taiwan--a population-based study.

Background: A mass Japanese encephalitis (JE) vaccination program targeting children was launched in Taiwan in 1968, and the number of pediatric JE cases substantially decreased thereafter. The aim of this study was to elucidate the long-term trend of JE incidence, and to investigate the age-specific seroprevalence of JE-neutralizing antibodies.

Methodology/principal Findings: A total of 2,948 laboratory-confirmed JE cases that occurred between 1966 and 2012 were analyzed using a mandatory notification system managed by the Centers for Disease Control, Taiwan.

Molecular characterization and phylogenetic analysis of dengue viruses imported into Taiwan during 2008-2010.

We present our surveillance results on imported dengue cases in Taiwan during 2008-2010. A total of 734 imported dengue patients were identified. The travelers were arriving from 18 countries, including Southeast Asia, the Indian subcontinent, South Pacific islands, and Latin America.

Analysis of epitopes on dengue virus envelope protein recognized by monoclonal antibodies and polyclonal human sera by a high throughput assay.

Background: The envelope (E) protein of dengue virus (DENV) is the major target of neutralizing antibodies and vaccine development. While previous studies on domain III or domain I/II alone have reported several epitopes of monoclonal antibodies (mAbs) against DENV E protein, the possibility of interdomain epitopes and the relationship between epitopes and neutralizing potency remain largely unexplored.

Methodology/principal Findings: We developed a dot blot assay by using 67 alanine mutants of predicted surface-exposed E residues as a systematic approach to identify epitopes recognized by mAbs and polyclonal sera, and confirmed our findings using a capture-ELISA assay.

Prevalence of Rickettsia felis and the first identification of Bartonella henselae Fizz/CAL-1 in cat fleas (Siphonaptera: Pulicidae) from Taiwan.

Cat fleas (Ctenocephalides felis [Bouché]) are the primary ectoparasites of dog and cat populations. In this study, we report the monthly population dynamics of Rickettsia felis and Bartonella spp. (two zoonotic pathogens that can cause human disease) in cat fleas collected from dogs and cats in Taipei, Taiwan, from December 2006 to December 2007.

Screening of dengue virus in field-caught Aedes aegypti and Aedes albopictus (Diptera: Culicidae) by one-step SYBR green-based reverse transcriptase-polymerase chain reaction assay during 2004-2007 in Southern Taiwan.

We carried out virological surveillance of dengue virus (DENV) in field-caught Aedes mosquitoes during 2004-2007 to estimate the monthly prevalence of infected females in dengue high-risk areas of Taiwan. A total of 92,892 Aedes aegypti (43,133 females and 49,759 males) and 79,315 Aedes albopictus (57,319 females and 21,996 males) adults were collected, grouped into 25,654 pools, and processed for virus detection using a one-step SYBR Green-based real-time reverse transcriptase-polymerase chain reaction assay. DENVs were periodically and sympatrically detected in Ae.

Concurrent isolation of chikungunya virus and dengue virus from a patient with coinfection resulting from a trip to Singapore.

We report two cases of imported infection in patients who had returned to Taiwan from Singapore: one was coinfected with chikungunya virus and dengue virus type 2, and the other was infected with the same dengue virus. Both viruses were successfully isolated from the coinfected case by using antibody neutralization and a plaque purification technique.

Phylogenetic analysis of 56-kDa type-specific antigen gene of Orientia tsutsugamushi isolates in Taiwan.

Scrub typhus is a rickettsial disease transmitted to humans through the bite of chigger mites infected with Orientia tsutsugamushi, and is an endemic disease in Taiwan. To elucidate the molecular epidemiology of O. tsutsugamushi, the complete open reading frame of the 56-kDa type-specific antigen gene sequence of strains isolated from scrub typhus patients were determined and analyzed.

Screening of mosquitoes using SYBR Green I-based real-time RT-PCR with group-specific primers for detection of Flaviviruses and Alphaviruses in Taiwan.

Surveillance for infectious agents carried by mosquitoes is important for predicting the risk of vector-borne infectious diseases. In this study, a method was established to mass-screen mosquitoes for viral infections. The assay detected the viral load of 4 dengue virus (DENV) serotypes (DENV-1, DENV-2, DENV-3, and DENV-4), the Japanese encephalitis virus (JEV), the Sindbis virus and the Chikungunya virus at 1PFU/mL (determined by real-time RT-PCR) in 36.

Effect of serotypes on clinical manifestations of dengue fever in adults.

Background And Purpose: Dengue fever (DF) is a major public health issue. However, it is unclear whether different dengue virus serotypes (DENV) are associated with different clinical manifestations and outcomes. This study investigated the association between viral serotype and clinical manifestations of DF.

African tick bite Fever in a Taiwanese traveler returning from South Africa: molecular and serologic studies.

We report the first imported case of African tick bite fever (ATBF) in a patient from Taiwan who returned from a 10-day trip to South Africa. Diagnosis was confirmed by polymerase chain reaction (PCR) from eschar biopsies. Portions of rickettsial ompA (491 bp) and ompB (273 bp) genes were amplified and subsequent sequencing of PCR product showed its 100% identity with R.

Molecular characterization of dengue viruses imported into Taiwan during 2003-2007: geographic distribution and genotype shift.

We presented our surveillance results on imported dengue cases in Taiwan during 2003-2007. A total of 542 imported dengue patients were identified. The travelers were infected in 17 countries in Southeast Asia, the Indian subcontinent, East African islands, South Pacific islands, and Central America.

Application of the dengue virus NS1 antigen rapid test for on-site detection of imported dengue cases at airports.

We used the dengue virus NS1 antigen (Ag) rapid test for on-site detection of imported dengue cases at airports. Among 22 positive cases of dengue identified from 850 patients with a fever suspected to have dengue, 17 were NS1 Ag test positive. These findings demonstrate the usefulness of the NS1 Ag rapid test in screening imported dengue cases at airports.

Rickettsia felis in cat fleas in Taiwan.

We describe the first detection of Rickettsia felis in cat fleas (Ctenocephalides felis) in Taiwan. Natural infections of R. felis in cat fleas were isolated and confirmed using polymerase chain reaction (PCR) and an immunofluorescence assay.

Retrospective serological study on sequential dengue virus serotypes 1 to 4 epidemics in Tainan City, Taiwan, 1994 to 2000.

Background And Purpose: We previously reported the development of a non-structural protein NS1 serotype-specific immunoglobulin G (IgG) enzyme-linked immunosorbent assay (ELISA) for dengue serodiagnosis and seroepidemiological study. This assay can be used to differentiate the immunologic status of individuals into naive, primary, or secondary dengue virus (DENV) infection and identify the DENV serotypes of primary infection. A retrospective study was conducted to investigate the serological responses of confirmed dengue cases infected during each of the sequential DENV-1 (August 1994 to February 1995), DENV-2 (August to December 1997), DENV-3 (August 1998 to January 1999), and DENV-4 (June to December 2000) epidemics in Tainan City, Taiwan.

Two clustering diffusion patterns identified from the 2001-2003 dengue epidemic, Kaohsiung, Taiwan.

This study analyzed the spatio-temporal patterns of 4,587 (94% of the total) confirmed dengue cases in Kaohsiung and Fengshan Cities (a two-city area) that occurred in Taiwan from 2001 to 2003. The epidemic had two simultaneous distinct diffusion patterns. One was a contiguous pattern, mostly limited to 1 km from an initial cluster, reflecting that there was a rapid dispersal of infected Aedes aegypti and viremic persons.

Isolation and identification of a novel spotted fever group rickettsia, strain IG-1, from Ixodes granulatus ticks collected on Orchid Island (Lanyu), Taiwan.

A novel species of spotted fever group (SFG) rickettsia, Rickettsia spp. IG-1, was identified and isolated from adult Ixodes granulatus ticks collected from Orchid Island (Lanyu), an islet located in southeastern Taiwan. Serum samples collected from the rodent host Rattus losea and SFG-positive human serum reacted with IG-1 using an immunofluorescence assay (IFA).

Comparative analysis of full genomic sequences among different genotypes of dengue virus type 3.

Background: Although the previous study demonstrated the envelope protein of dengue viruses is under purifying selection pressure, little is known about the genetic differences of full-length viral genomes of DENV-3. In our study, complete genomic sequencing of DENV-3 strains collected from different geographical locations and isolation years were determined and the sequence diversity as well as selection pressure sites in the DENV genome other than within the E gene were also analyzed.

Results: Using maximum likelihood and Bayesian approaches, our phylogenetic analysis revealed that the Taiwan's indigenous DENV-3 isolated from 1994 and 1998 dengue/DHF epidemics and one 1999 sporadic case were of the three different genotypes - I, II, and III, each associated with DENV-3 circulating in Indonesia, Thailand and Sri Lanka, respectively.

Laboratory-based dengue surveillance in Taiwan, 2005: a molecular epidemiologic study.

We present the results of laboratory-based dengue surveillance in Taiwan for 2005. A phylogenetic study showed that multiple dengue epidemics were caused by three different imported dengue virus (DENV) strains. A strain of DENV-3 (genotype I) imported from the Philippines first appeared in the southern part of Kaohsiung City and later spread to Kaohsiung County from August to December, which resulted in 77 cases of dengue.

Seaport as a source of hantavirus: a study on isolated isles.

Since small mammals from seaports have relative higher seroprevalences of hantavirus, this seroepidemiologic study was conducted on the isles in Kinmen and Lienchiang Counties along the coast of southern mainland China to determine whether seaport may play the role as a source of hantavirus. Among six species of small mammals trapped in Kinmen County, only male Mus musculus (6.7%) and Rattus losea (5.

Slower rates of clearance of viral load and virus-containing immune complexes in patients with dengue hemorrhagic fever.

Background: Although previous studies have revealed the contribution of an initial high level of dengue virus replication to the severe and potentially life-threatening diseases dengue hemorrhagic fever (DHF) and dengue shock syndrome, the involvement of dengue virus in the immunopathological processes during the transition from fever to defervescence, which is a critical stage in determining the progression to DHF, has not been appreciated. Previously, we reported that dengue virus can be detected in the immune complexes of patients with DHF during this period.

Methods: We investigated plasma dengue viral load, virus in immune complexes, antibody response, complements, and cytokines for 54 patients with dengue fever (a relatively mild form of disease) and 49 patients with DHF.