Differentiating New from Newly Detected: Melioidosis in Yap, Federated States of Micronesia.

Melioidosis is a bacterial infection caused by exposure to water or soil that contains Burkholderia pseudomallei (Bp). Burkholderia pseudomallei is endemic to many tropical and subtropical areas of the world. In 2013, the first case of melioidosis was recognized in Yap, the Federated States of Micronesia. Six additional cases were identified in the subsequent 3 years. An investigation was initiated to understand the epidemiology of melioidosis in Yap. Serum from family and community members of the identified cases were tested for antibodies to Bp. Archived serum from a 2007 Zika serosurvey were also tested for antibodies to Bp. Sequencing of bacterial isolates was performed to understand bacterial phylogeny. Soil and water were tested for the presence of Bp in the environment by culture and PCR. None of the affected patients had a history of travel to melioidosis-endemic countries. Two of the 34 (5.8%) samples from the field investigation and 67 (11.7%) of the historical samples demonstrated serologic evidence of prior Bp exposure. No Bp were detected from 30 soil or water samples. Genotype analysis showed highly related Bp isolates that were unique to Yap. Melioidosis is likely to be endemic to Yap; however, it has only recently been recognized by the clinical community in country. Further investigation is needed to understand the local sites that harbor Bp and represent the highest risk to the community.

Chikungunya virus disease outbreak in Yap State, Federated States of Micronesia.

BACKGROUND: Chikungunya virus is a mosquito-borne alphavirus which causes an acute febrile illness associated with polyarthralgia. Beginning in August 2013, clinicians from the Yap State Department of Health in the Federated States of Micronesia (FSM) identified an unusual cluster of illness which was subsequently confirmed to be chikungunya virus disease. Chikungunya virus disease previously had not been recognized in FSM. METHODOLOGY/PRINCIPAL FINDINGS: Information from patients presenting to healthcare facilities was collected and analyzed. During August 11, 2013, to August 10, 2014, a total of 1,761 clinical cases were reported for an attack rate of 155 clinical cases per 1,000 population. Among residents of Yap Main Island, 3% were hospitalized. There were no deaths. The outbreak began on Yap Main Island and rapidly spread throughout Yap Main Island and to three neighboring islands. CONCLUSIONS/SIGNIFICANCE: Chikungunya virus can cause explosive outbreaks with substantial morbidity. Given the increasing globalization of chikungunya virus, strong surveillance systems and access to laboratory testing are essential to detect outbreaks.

Use of a Rapid Test for Diagnosis of Dengue during Suspected Dengue Outbreaks in Resource-Limited Regions.

Dengue is major public health problem, globally. Timely verification of suspected dengue outbreaks allows for public health response, leading to the initiation of appropriate clinical care. Because the clinical presentation of dengue is nonspecific, dengue diagnosis would benefit from a sensitive rapid diagnostic test (RDT). We evaluated the diagnostic performance of an RDT that detects dengue virus (DENV) nonstructural protein 1 (NS1) and anti-DENV IgM during suspected acute febrile illness (AFI) outbreaks in four countries. Real-time reverse transcription-PCR and anti-DENV IgM enzyme-linked immunosorbent assay were used to verify RDT results. Anti-DENV IgM RDT sensitivity and specificity ranged from 55.3 to 91.7% and 85.3 to 98.5%, respectively, and NS1 sensitivity and specificity ranged from 49.7 to 92.9% and 22.2 to 89.0%, respectively. Sensitivity varied by timing of specimen collection and DENV serotype. Combined test results moderately improved the sensitivity. The use of RDTs identified dengue as the cause of AFI outbreaks where reference diagnostic testing was limited or unavailable.

Incrimination of Aedes (Stegomyia) hensilli Farner as an epidemic vector of Chikungunya virus on Yap Island, Federated States of Micronesia, 2013.

Two species of Aedes (Stegomyia) were collected in response to the first chikungunya virus (CHIKV) outbreak on Yap Island: the native species Ae. hensilli Farner and the introduced species Ae. aegypti (L.). Fourteen CHIKV-positive mosquito pools were detected. Six pools were composed of female Ae. hensilli, six pools were composed of female Ae. aegypti, one pool was composed of male Ae. hensilli, and one pool contained female specimens identified as Ae. (Stg.) spp. Infection rates were not significantly different between female Ae. hensilli and Ae. aegypti. The occurrence of human cases in all areas of Yap Island and the greater number of sites that yielded virus from Ae. hensilli combined with the ubiquitous distribution of this species incriminate Ae. hensilli as the most important vector of CHIKV during the outbreak. Phylogenic analysis shows that virus strains on Yap are members of the Asia lineage and closely related to strains currently circulating in the Caribbean.

Aedes hensilli as a potential vector of Chikungunya and Zika viruses.

An epidemic of Zika virus (ZIKV) illness that occurred in July 2007 on Yap Island in the Federated States of Micronesia prompted entomological studies to identify both the primary vector(s) involved in transmission and the ecological parameters contributing to the outbreak. Larval and pupal surveys were performed to identify the major containers serving as oviposition habitat for the likely vector(s). Adult mosquitoes were also collected by backpack aspiration, light trap, and gravid traps at select sites around the capital city. The predominant species found on the island was Aedes (Stegomyia) hensilli. No virus isolates were obtained from the adult field material collected, nor did any of the immature mosquitoes that were allowed to emerge to adulthood contain viable virus or nucleic acid. Therefore, laboratory studies of the probable vector, Ae. hensilli, were undertaken to determine the likelihood of this species serving as a vector for Zika virus and other arboviruses. Infection rates of up to 86%, 62%, and 20% and dissemination rates of 23%, 80%, and 17% for Zika, chikungunya, and dengue-2 viruses respectively, were found supporting the possibility that this species served as a vector during the Zika outbreak and that it could play a role in transmitting other medically important arboviruses.

Improvement of leptospirosis surveillance in remote Pacific islands using serum spotted on filter paper.

OBJECTIVES: Leptospirosis is a serious neglected disease in the Pacific. Because sensitive and specific laboratory tests are largely unavailable, the burden of disease and epidemiological data are often unreliable and do not allow informed disease prioritization and efficient control. We report the use of serum spotted on filter paper to improve the surveillance of leptospirosis in remote and resource-limited settings. METHODS: A total of 172 acute-phase serum samples collected from patients with suspected dengue at Yap State Hospital, Federated States of Micronesia, were spotted on filter paper and sent by regular mail to the Institut Louis Malardé, French Polynesia. Real-time PCR protocols for dengue and leptospirosis confirmation were performed on all specimens. RESULTS: A total of five leptospirosis infections were detected amongst the patients with suspected dengue. CONCLUSIONS: This study confirms the use of filter paper as a convenient tool to improve leptospirosis surveillance capacity in remote areas. New surveillance strategies, notably based on the regular use of this type of tool, are essential to more adequately describe the epidemiology and burden of neglected diseases.

Use of serum and blood samples on filter paper to improve the surveillance of Dengue in Pacific Island Countries.

BACKGROUND: In Pacific Island Countries (PICs) the epidemiology of dengue is characterized by long-term transmission of a single dengue virus (DENV) serotype. The emergence of a new serotype in one island country often indicates major outbreaks with this serotype will follow in other PICs. OBJECTIVES: Filter paper (FP) cards on which whole blood or serum from dengue suspected patients had been dried was evaluated as a method for transportation of this material by standard mail delivery throughout the Pacific. STUDY DESIGN: Twenty-two FP-dried whole blood samples collected from patients in New Caledonia and Wallis & Futuna Islands, during DENV-1 and DENV-4 transmission, and 76 FP-dried sera collected from patients in Yap State, Majuro (Republic of Marshall Islands), Tonga and Fiji, before and during outbreaks of DENV-2 in Yap State and DENV-4 in Majuro, were tested for the presence of DENV RNA, by serotype specific RT-PCR, at the Institut Louis Malardé in French Polynesia. RESULTS: The serotype of DENV could be determined, by a variety of RT-PCR procedures, in the FP-dried samples after more than three weeks of transport at ambient temperatures. In most cases, the sequencing of the envelope gene to genotype the viruses also was possible. CONCLUSIONS: The serotype and genotype of DENV can be determined from FP-dried serum or whole blood samples transported over thousands of kilometers at ambient, tropical, temperatures. This simple and low-cost approach to virus identification should be evaluated in isolated and resource poor settings for surveillance for a range of significant viral diseases.

Zika virus outbreak on Yap Island, Federated States of Micronesia.

BACKGROUND: In 2007, physicians on Yap Island reported an outbreak of illness characterized by rash, conjunctivitis, and arthralgia. Although serum from some patients had IgM antibody against dengue virus, the illness seemed clinically distinct from previously detected dengue. Subsequent testing with the use of consensus primers detected Zika virus RNA in the serum of the patients but no dengue virus or other arboviral RNA. No previous outbreaks and only 14 cases of Zika virus disease have been previously documented. METHODS: We obtained serum samples from patients and interviewed patients for information on clinical signs and symptoms. Zika virus disease was confirmed by a finding of Zika virus RNA or a specific neutralizing antibody response to Zika virus in the serum. Patients with IgM antibody against Zika virus who had a potentially cross-reactive neutralizing-antibody response were classified as having probable Zika virus disease. We conducted a household survey to estimate the proportion of Yap residents with IgM antibody against Zika virus and to identify possible mosquito vectors of Zika virus. RESULTS: We identified 49 confirmed and 59 probable cases of Zika virus disease. The patients resided in 9 of the 10 municipalities on Yap. Rash, fever, arthralgia, and conjunctivitis were common symptoms. No hospitalizations, hemorrhagic manifestations, or deaths due to Zika virus were reported. We estimated that 73% (95% confidence interval, 68 to 77) of Yap residents 3 years of age or older had been recently infected with Zika virus. Aedes hensilli was the predominant mosquito species identified. CONCLUSIONS: This outbreak of Zika virus illness in Micronesia represents transmission of Zika virus outside Africa and Asia. Although most patients had mild illness, clinicians and public health officials should be aware of the risk of further expansion of Zika virus transmission.

An outbreak of dengue fever in Yap State.

Between May and December 2004,Yap State experienced an outbreak of Dengue Fever, type 1 with a final total of 658 recorded clinically compatible cases, including 42 hospitalisations and 12 cases of dengue haemorrhagic fever/shock syndrome. There were no fatalities. Lessons learned from this outbreak include: the importance maintaining a high index of suspicion and on-site diagnostic capability for dengue fever, the importance of prompt in-service training for health care workers, the danger posed to neighbors by local lapses in outbreak prone disease surveillance and the utility of the Pacific Public Health Surveillance Network in responding to such diseases, the importance of active disease surveillance in outer island populations, and the importance of instituting preventive measures against the nosocomial spread of dengue fever.