Niue Research Articles

Abiotic and Biotic Processes Controlling Deposition of Calcite and Hydrotalcite Calcretes on Niue Island, Southwest Pacific

Calcretes are indurated terrestrial carbonates that are widespread in arid and semi-arid settings and serve as important archives of present and past environments. Here, we use geochemical tools to explore the nature and origin of calcretes documented from tropical Niue Island in the Southwest Pacific. The study recognizes two types of calcretes that differ in their mineral assemblage, microfabrics, elemental chemistry, and carbon and oxygen isotopes. The calcretes common in the paleo-lagoon soils consist of 90% low-Mg calcite and ~10% highly weathered Mg-Al silicates. These pedogenic calcretes formed in the soil profiles within the vadose zone bear the following distinctions: (i) Fe/Al ratio of 0.75, identical to the ratio in soils (Fe/Al = 0.76 ± 0.5), substantiating the link between the calcretes and soils; (ii) presence of rhizoliths, root voids, micritic nodules, and clasts, which are consistent with a pedogenic calcrete fabric; and (iii) 13C and 18O depletions of −10.6‰ and −5.3‰, respectively, which are compatible with carbon sources from microbial and root respiration, as well as formation in oxygen isotope equilibrium with vadose waters. Unlike the pedogenic calcrete, a rare calcrete from the coastal terrace contains an exceptionally rare hydrotalcite [Mg6Al2(CO3)(OH)16(H2O)4] mineral (65%) coated by microbial films. We contend that the hydrotalcite-rich calcrete was deposited through interaction of dolomite with seawater, similar to the method of producing hydrotalcite in the laboratory. 13C and 18O enrichments of 0.8 to 1.7‰ and −1.0 to −1.6‰, respectively, are in agreement with (i) mixed carbon sources consisting of microbial CO2 degassing, seawater HCO3, and dolomite dissolution, and (ii) oxygen isotope equilibration with seawater-derived fluid.

Mid‐Holocene rainfall seasonality and ENSO dynamics over the south‐western Pacific

AbstractEl Niño–Southern Oscillation dynamics affect global weather patterns, with regionally diverse hydrological responses posing critical societal challenges. The lack of seasonally resolved hydrological proxy reconstructions beyond the observational era limits our understanding of boundary conditions that drive and/or adjust El Niño–Southern Oscillation variability. Detailed reconstructions of past El Niño–Southern Oscillation dynamics can help modelling efforts, highlight impacts on disparate ecosystems and link to extreme events that affect populations from the tropics to high latitudes. Here, mid‐Holocene El Niño–Southern Oscillation and hydrological changes are reconstructed in the south‐west Pacific using a stalagmite from Niue Island, which represents the period 6.4–5.4 ka BP. Stable oxygen and carbon isotope ratios, trace elements and greyscale data from a U/Th‐dated and layer counted stalagmite profile are combined to infer changes in local hydrology at sub‐annual to multi‐decadal timescales. Principal component analysis reveals seasonal‐scale hydrological changes expressed as variations in stalagmite growth patterns and geochemical characteristics. Higher levels of host rock‐derived elements (Sr/Ca and U/Ca) and higher δ18O and δ13C values are observed in dark, dense calcite laminae deposited during the dry season, whereas during the wet season, higher concentrations of soil‐derived elements (Zn/Ca and Mn/Ca) and lower δ18O and δ13C values are recorded in pale, porous calcite laminae. The multi‐proxy record from Niue shows seasonal cycles associated with hydrological changes controlled by the positioning and strength of the South Pacific Convergence Zone. Wavelet analysis of the greyscale record reveals that El Niño–Southern Oscillation was continuously active during the mid‐Holocene, with two weaker intervals at 6–5.9 and 5.6–5.5 ka BP. El Niño–Southern Oscillation especially affects dry season rainfall dynamics, with increased cyclone activity that reduces hydrological seasonality during El Niño years.

Sampling rate-corrected analysis of irregularly sampled time series.

The analysis of irregularly sampled time series remains a challenging task requiring methods that account for continuous and abrupt changes of sampling resolution without introducing additional biases. The edit distance is an effective metric to quantitatively compare time series segments of unequal length by computing the cost of transforming one segment into the other. We show that transformation costs generally exhibit a nontrivial relationship with local sampling rate. If the sampling resolution undergoes strong variations, this effect impedes unbiased comparison between different time episodes. We study the impact of this effect on recurrence quantification analysis, a framework that is well suited for identifying regime shifts in nonlinear time series. A constrained randomization approach is put forward to correct for the biased recurrence quantification measures. This strategy involves the generation of a type of time series and time axis surrogates which we call sampling-rate-constrained (SRC) surrogates. We demonstrate the effectiveness of the proposed approach with a synthetic example and an irregularly sampled speleothem proxy record from Niue island in the central tropical Pacific. Application of the proposed correction scheme identifies a spurious transition that is solely imposed by an abrupt shift in sampling rate and uncovers periods of reduced seasonal rainfall predictability associated with enhanced El Niño-Southern Oscillation and tropical cyclone activity.

Phenotypic Features of Dimya cf. Japonica (Bivalvia, Dimyidae) from Niue Island (South Pacific) with Accounts on Its Phylogeny and Taxonomic Relationships

Phenotypic characters of the uncommon Dimya cf. japonica, based on a specimen from Niue Is. in the South Pacific, are reported to represent the enigmatic Dimyidae in a wide-ranging Bivalvia phylogenetic scenario. The main conclusion is that dimyids are placed between ostreoideans and pectinoideans. This is supported by five synapomorphies. Dimyids are closer to pectinoideans, in that they share four synapomorphies.

The Weapon Beneath the Woodpile

This article is a tribute to the late Auckland historian Dick Scott, whose 1954 The Story of Parihaka became one of the most influential historical works published in this country. Scott’s other best-known works are left-wing exposés of historical events, such as Would a Good Man Die? Niue Island, New Zealand and the Late Mr Larsen (1993). Others are local histories, including Seven Lives on Salt River (1987), an account of the watery district of Pāhi on the Kaipara Harbour. The remainder are industry or company histories, and particularly histories of New Zealand’s wine industry.

A narrative review of noncommunicable diseases in the Pacific region: A case study of the island of Niue

INTRODUCTION This literature review takes a strengths-based approach to explore and contextualise noncommunicable diseases in the Pacific region. It compares the noncommunicable disease profile of Niue to that of the Pacific region. METHODS The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) framework was used to search for and screen literature published from 2010 to 2020 pertaining to noncommunicable diseases in the Pacific region. Twenty-five pieces of literature were included in the final data synthesis. RESULTS Noncommunicable diseases are a burgeoning issue for the Pacific region. The literature revealed that the risk factors arise from a complex set of socio-political and historical factors, including poverty, colonisation, globalisation, urbanisation, climate change, and poor health system infrastructure. The literature indicated that the noncommunicable disease trends of Niue do not differ greatly from those of the Pacific region. Where Niue does differ is in factors related to its relationship with Aotearoa New Zealand, and issues related to outmigration and the subsequently small population size. CONCLUSION This literature review was conducted in a way that endeavoured to avoid victim-blaming, by drawing attention to the broader social, political, and historical contexts in which the Pacific exists. Solutions to the noncommunicable disease crisis must take these contexts into consideration and focus on supporting local capacity and self-determination.

Mens perception of health and health services on the Island of Niue: a qualitative study

Background Men on the small Pacific island of Niue suffer from a range of health conditions but underuse health services. This study aimed to understand why. Very little is known about how men living in Niue view health and wellbeing. Knowing more would help to target services to meet men’s needs. Methods Qualitative face to face interviews were undertaken with a convenience sample of twenty men in Niue aged between 26 and 75 years. Data were analysed using a general inductive approach to identify recurring themes. Ethical approval for the study was obtained from the University of Auckland Human Participants ethics committee. Results The men interviewed had good knowledge of healthy and unhealthy behaviours. They believed that day to day activities such as working on plantations, fishing, and consuming healthy foods helped them to stay healthy and happy. They identified unhealthy diets as a major contributor to high blood pressure, high cholesterol, diabetes and gout. Traditional medicine was commonly used by older men in preference to formal healthcare services. All of the participants had a good knowledge about the health services available in Niue, but most said that conceptions of masculinity, pride and stubbornness influenced them not to visit doctors. They found it easier to speak about health issues with professionals who were able to communicate in the Niuean language. There was a consensus that providing health promotion workshops and exercise programmes in local villages would be beneficial. Conclusions This small study did not aim to generalise to all men in Niue, but it suggests that there is scope for local communities and health services to work together to improve men’s health. The consistency of findings suggests that men in Niue know what constitutes unhealthy behaviours, but they may not feel comfortable visiting health services for support. This may be because they do not trust health services, do not think it would be ‘manly’ to visit such services or are afraid to be diagnosed with illnesses and become a ‘burden’. Positively, men are open to taking part in health promotion workshops and exercise programmes in villages, and this could help to develop more acceptance of positive health behaviours.

Pasifika Medical Association 23rd Conference Niue 24–26 September 2019

Pasifika Medical Association Conference 2019: The Rising Tide Statement, 26 September 2019

Redescription of Favognathus insularis (Luxton) (Acari: Trombidiformes: Cryptognathidae) from Brazil, with a key to the world species of Favognathus

Until now, Favognathus insularis (Luxton, 1973) has been only known from the Niue Island. In recent surveys conducted in the Brazilian state of Sao Paulo, a second record of this species was provided. It is redescribed here based on the adult females. Also, an identification key to known species of Favognathus is provided.

The 6–8 Aug 2019 eruption of ‘Volcano F’ in the Tofua Arc, Tonga

In August 2019 a large raft of pumice appeared in the territorial waters of Tonga. As in many other cases, this pumice raft was the only surface expression of a major submarine volcanic eruption. Discolored water and reconstruction of the drift path of the pumice raft using satellite imagery points towards ‘Volcano F’ in the Tofua Arc NW of the island of Vava’u as the most likely volcanic source. Here we present imagery from ESA’s Sentinel-2 satellite that captured the start of the submarine eruption on 6 August 2019 and the waning of the eruption on 8 August, followed by observations of the drifting pumice raft until 14 August. This start time is consistent with T-phase records at the seismic stations on Niue Island and Rarotonga and the signal delay time of 733s between the two stations is consistent with an origin at or at least near Volcano F. On 8 August, a >136.7 km2 large raft of pumice appears at the sea surface. The modelled minimum raft volume is 8.2–41.0*106m3, which is equivalent to 2.5–12.3*106m3 dense rock. The eruption thus corresponds to a volcanic explosivity index (VEI) 2–3 eruption in the submarine environment. Prior to the volcanic eruption, a series of earthquakes close to Volcano F was recorded. The series started on 5 August with a Mb 4.7 event, followed by at least six shallow earthquakes (Mb >3.9) on 6 August. In December 2018 and January 2019, we surveyed the seafloor around Volcano F with multibeam sonar. Combining our data with pre-existing information, we present the first comprehensive bathymetric map of the volcanic edifice and its geologic setting. We show that Volcano F represents a major arc volcanic complex that is situated in an extensional setting. The basal diameter of the volcanic apron is >50km with a large central, 8.7x6km caldera with a floor at ∼700m water depth. The top of the post-caldera constructional cone complex had a summit depth of 35m below sea level in 2004. The volcano shows geochemical differences to the adjacent arc volcanoes on Fonualei and Late islands. The volcano’s pristine volcanic morphology and two documented eruptions (2001 and 2019) indicate a highly active volcanic system that warrants further scientific attention.

Meso-zooplankton structure and functioning in the western tropical South Pacific along the 20th parallel south during the OUTPACE survey (February–April 2015)

Abstract. The western tropical South Pacific (WTSP) is one of the most understudied oceanic regions in terms of the planktonic food web, despite supporting some of the largest tuna fisheries in the world. In this stratified oligotrophic ocean, nitrogen fixation may play an important role in supporting the plankton food web and higher trophic level production. In the austral summer (February–April) of 2015, the OUTPACE (Oligotrophy to UlTra-oligotrophy PACific Experiment) project conducted a comprehensive survey of 4000 km along 20∘ S, from New Caledonia to Tahiti, to determine the role of N2 fixation on biogeochemical cycles and food web structure in this region. Here, we characterize the zooplankton community and plankton food web processes at 15 short-duration stations (8 h each) to describe the large-scale variability across trophic gradients from oligotrophic waters around Melanesian archipelagoes (MAs) to ultra-oligotrophic waters of the South Pacific gyre (GY). Three long-duration stations (5 days each) enabled a more detailed analysis of processes and were positioned (1) in offshore northern waters of New Caledonia (MA), (2) near Niue Island (MA), and (3) in the subtropical Pacific gyre (GY) near the Cook Islands. At all stations, meso-zooplankton was sampled with a bongo net with 120 µm mesh size to estimate abundance, biomass, community taxonomy and size structure, and size fractionated δ15N. Subsequently, we estimated zooplankton carbon demand, grazing impact, excretion rates, and the contribution of diazotroph-derived nitrogen (DDN) to zooplankton biomass. The meso-zooplankton community showed a general decreasing trend in abundance and biomass from west to east, with a clear drop in the GY waters. Higher abundance and biomass corresponded to higher primary production associated with complex mesoscale circulation in the Coral Sea and between 170–180∘ W. The taxonomic structure showed a high degree of similarity in terms of species richness and abundance distribution across the whole region, with, however, a moderate difference in the GY region, where the copepod contribution to meso-zooplankton increased. The calculated ingestion and metabolic rates allowed us to estimate that the top–down (grazing) and bottom–up (excretion of nitrogen and phosphorous) impact of zooplankton on phytoplankton was potentially high. Daily grazing pressure on phytoplankton stocks was estimated to remove 19 % to 184 % of the total daily primary production and 1.5 % to 22 % of fixed N2. The top–down impact of meso-zooplankton was higher in the eastern part of the transect, including GY, than in the Coral Sea region and was mainly exerted on nano- and micro-phytoplankton. The regeneration of nutrients by zooplankton excretion was high, suggesting a strong contribution to regenerated production, particularly in terms of N. Daily NH4+ excretion accounted for 14.5 % to 165 % of phytoplankton needs for N, whereas PO43- excretion accounted for only 2.8 % to 34 % of P needs. From zooplankton δ15N values, we estimated that the DDN contributed to up to 67 % and 75 % to the zooplankton biomass in the western and central parts of the MA regions, respectively, but strongly decreased to an average of 22 % in the GY region and down to 7 % in the easternmost station. Thus, the highest contribution of diazotrophic microorganisms to zooplankton biomass occurred in the region of highest N2 fixation rates and when Trichodesmium dominated the diazotrophs community (MA waters). Our estimations of the fluxes associated with zooplankton were highly variable between stations and zones but very high in most cases compared to literature data, partially due to the high contribution of small forms. The highest values encountered were found at the boundary between the oligotrophic (MA) and ultra-oligotrophic regions (GY). Within the MA zone, the high variability of the top–down and bottom–up impact was related to the high mesoscale activity in the physical environment. Estimated zooplankton respiration rates relative to primary production were among the highest cited values at similar latitudes, inducing a high contribution of migrant zooplankton respiration to carbon flux. Despite the relatively low biomass values of planktonic components in quasi-steady state, the availability of micro- and macronutrients related to physical mesoscale patterns in the waters surrounding the MA, the fueling by DDN, and the relatively high rates of plankton production and metabolism estimated during OUTPACE may explain the productive food chain ending with valuable fisheries in this region.

Interview with Dr Colin Tukuitonga: from crisis to action in Pacific communities.

The island communities in the Pacific contribute very little to global carbon emissions, yet they are among the most vulnerable to the effects of climate change. Dr Colin Tukuitonga, a general practitioner by training, was born and raised on Niue Island in the Pacific. He has held senior public health roles in the New Zealand Government and, since 2014, has served as Pacific Community Director-General. He spoke to us about how climate change is affecting the health of people living in Pacific Island countries and the relevance of Australia's climate change policy responses to these neighbouring countries.

Niuean

Niuean (ISO 639-3 code niu) is a Polynesian language spoken on the island of Niue, with an additional population of speakers living in New Zealand. Figure 1 indicates where Niue is located with respect to other neighboring islands in the South Pacific. The 2011 Niue Census of Populations and Households cited the number of individuals who had either basic or fluent spoken abilities at 1121 (with 101 non-speakers) (Statistics Niue 2012). English is the second most widely used language on the island. The 2013 New Zealand census cited 4548 individuals living in New Zealand who listed Niuean as one of their languages (Statistics New Zealand 2013). Niuean is classified as ‘definitely endangered’ by UNESCO (Moseley 2010). There are historically two distinct dialects: the older Motu dialect from the northern area, and the more recent Tafiti from the southern area. These dialect differences were once reflected in slight phonological differences in vocabulary items, but the differences have since eroded in the modern language (see McEwen 1970: ix). Previous research on Niuean phonetics and phonology includes a brief outline in Seiter (1980: x), two dictionaries (McEwen 1970, Sperlich 1997), and an article on vowel length (Rolle & Starks 2014). While these works provide an overview of some of the phenomena to be addressed below, this sketch attempts a more thorough documentation of the phonetic structures of Niuean, and provides novel acoustic and articulatory data from the language. Recordings accompanying this paper are of a male speaker (Mr. Krypton Okesene) and a female speaker (the second author).

The interaction between stratospheric monthly mean regional winds and sporadic-E

In the present study, a statistical investigation is carried out to explore whether there is a relationship between the critical frequency (foEs) of the sporadic-E layer that is occasionally seen on the E region of the ionosphere and the quasi-biennial oscillation (QBO) that flows in the east–west direction in the equatorial stratosphere. Multiple regression model as a statistical tool was used to determine the relationship between variables. In this model, the stationarity of the variables (foEs and QBO) was firstly analyzed for each station (Cocos Island, Gibilmanna, Niue Island, and Tahiti). Then, a co-integration test was made to determine the existence of a long-term relationship between QBO and foEs. After verifying the presence of a long-term relationship between the variables, the magnitude of the relationship between variables was further determined using the multiple regression model. As a result, it is concluded that the variations in foEs were explainable with QBO measured at 10 hPa altitude at the rate of 69%, 94%, 79%, and 58% for Cocos Island, Gibilmanna, Niue Island, and Tahiti stations, respectively. It is observed that the variations in foEs were explainable with QBO measured at 70 hPa altitude at the rate of 66%, 69%, 53%, and 47% for Cocos Island, Gibilmanna, Niue Island, and Tahiti stations, respectively.

A two-year automated dripwater chemistry study in a remote cave in the tropical south Pacific: Using [Cl−] as a conservative tracer for seasalt contribution of major cations

Stalagmite Mg/Ca and Sr/Ca ratios are commonly interpreted as proxies for past hydrologic conditions and are often used to supplement carbon and oxygen stable isotope records. While the processes that control these element ratios, including water–rock interaction, dripwater residence time, and upstream precipitation of calcite, are well understood in continental caves, there have been few investigations of dripwater Element/Ca (X/Ca) evolution in coastal marine caves where seasalt can have a strong influence on the incoming Mg/Ca ratio.We instrumented a marine cave on the remote South Pacific island of Niue to record daily cave microclimate, as well as weekly-integrated drip rates, dripwater oxygen and hydrogen isotopes, and dripwater chemistry over a period of twenty-two months. Using chloride as a conservative tracer for sea-spray, we calculate that seasalt input accounts for a large portion of dripwater Na, SO4, and Mg (89%, 93%, and 85% respectively) and a smaller portion of the Ca and Sr (19% and 17%). During the second year of this study a gradual decrease (by ∼18%) in dripwater chlorinity was observed, suggesting that an epikarst-hosted seasalt aerosol inventory was being diluted over time. Minor element to calcium ratios for B, K, Cl, SO4, Mg, Na, Sr, and Fe all strongly covary over the observation period, suggesting that although sea-spray plays a significant role in modulating incoming drip chemistry, prior calcite precipitation (PCP) dominates chemical evolution within the epikarst. During a prolonged drought episode, evaporative enrichments in dripwater δD and δ18O (+4‰ and 0.5‰, respectively) were observed to coincide with increased cation and anion concentrations, strong Ca removal via PCP, and increases in Sr/Ca and Mg/Ca ratios (28% and 34%, respectively), suggesting that concomitant enrichment in speleothem δ18O and X/Ca ratios may be interpreted as multi-proxy evidence for dry climate conditions.We use modern dripwater chemistry and empirical water-calcite distribution coefficients to predict a range of stalagmite X/Ca ratios. We then forward model a number of scenarios that could modulate stalagmite chemistry, including increased/decreased seasalt input and changing dripwater flow path through calcite, dolomite, and aragonite bedrock. One major implication from this study is that even if PCP and flow path lithology remain constant over time, changing seasalt input can drive stalagmite Mg/Ca and Sr/Ca ratios away from PCP-controlled covariation, and lead to strongly varying Sr/Mg ratios. Thus in order to interpret coastal cave stalagmite X/Ca records accurately, it is necessary to estimate seasalt input and analyze parent drip and bedrock chemistry to quantify the influence of each contributing process.

Niue, 1774-1974: 200 years of contact and change

Niue, 1774-1974: 200 years of contact and change

First report of Cladosporium colocasiae as a pathogen causing leaf spot disease on taro (Colocasia esculenta) in Iran.

During the Summer 2013, a new foliar disease was observed on taro (Colocasia esculenta) in tropical areas of Iran, including Hormozgan, where many farmers were alarmed by complete destruction of their taro cultivation. Leaf spots, yellow to dark brown, were subglobose and oval. A fungus was consistently isolated from diseased tissues on Potato Dextrose Agar (PDA) at 23± 2°C. Morphological observations were carried out on Synthetic Nutrient Agar (SNA) medium as described by Bensch et al. (2012). Conidiophores were macronematous, cylindrical-oblong with several nodes being quite apart from each other, very long, up to 350 μm or even longer. Conidia ellipsoid-subcylindrical to cylindrical, forming short, unbranched or branched chains. Terminal conidia were 9–16 × 5–8 μm and aseptate or 1-septate. A portion of the translation elongation factor 1-α gene was amplified (Bensch et al., 2012) and sequenced (GenBank Accession No. KP893386). A BLAST search showed 99% similarity with Cladosporium colocasiae sequences deposited in GenBank. To verify Koch’s postulates, pathogenicity was tested by spraying a conidial suspension prepared from cultures on PDA (1 x106 spores ml ) in sterile water on healthy leaves of four test plants (5- 7 leaf stage, cv. Niue). Control plants were sprayed with sterile water. Plants were kept in a greenhouse (average minimum temp. 24°C, max. 37°C and relative humidity 64%). Symptoms appeared 2 weeks post-inoculation on inoculated plants, whereas control plants remained asymptomatic. Reisolation of the pathogen with the same morphological characters was achieved from symptomatic plants only, hence confirming the causal agent as C. colocasiae. To our knowledge, this is the first report of C. colocasiae on C. esculenta in Iran.

Marginality in the South Pacific – the Example of Niue

Marginality in the South Pacific – the Example of Niue

MIS 7 interglacial sea-surface temperature and salinity reconstructions from a southwestern subtropical Pacific coral

We generated a 5.5-yr snapshot of biweekly-to-monthly resolved time series of carbon and oxygen isotope composition (δ13C and δ18O) and Sr/Ca and Mg/Ca from annually banded aragonite skeleton of a ~197ka pristine Porites coral collected at Niue Island (19°00′S, 169°50′W) in the southwestern subtropical Pacific Ocean. This report is the first of a high-resolution coral-based paleoclimate archive during the Marine Isotope Stage (MIS) 7 interglacial. Statistical results suggest that annual averages of sea-surface temperature (SST) and salinity (SSS) at ~197ka were not significantly different from and ~1.2 higher than at present, respectively. Monthly mean variations showed increased SSS at ~197ka that was higher (1.4–1.9 relative to today) in the austral summer than in the austral winter. Monthly SST and SSS anomalies at ~197ka indicated smaller amplitudes by ~0.3°C (11%) and ~0.3 (24%) relative to the present, possibly suggesting less influence of interannual climate variability around Niue. Our results, taken together with other climate proxy records, imply seasonal and interannual modulation of thermal and hydrological conditions, different from today, in the southwestern subtropical Pacific Ocean associated with the Western Pacific Warm Pool and the South Pacific Convergence Zone variability during the MIS 7 interglacial.

Natural attenuation of dengue virus type-2 after a series of island outbreaks: A retrospective phylogenetic study of events in the South Pacific three decades ago

Dengue is an expanding arboviral disease of variable severity characterized by the emergence of virus strains with greater fitness, epidemic potential and possibly virulence. To investigate the role of dengue virus (DENV) strain variation on epidemic activity we studied DENV-2 viruses from a series of South Pacific islands experiencing outbreaks of varying intensity and clinical severity. Initially appearing in 1971 in Tahiti and Fiji, the virus was responsible for subsequent epidemics in American Samoa, New Caledonia and Niue Island in 1972, reaching Tonga in 1973 where there was near-silent transmission for over a year. Based on whole-genome sequencing and phylogenetic analysis on 20 virus isolates, Tonga viruses were genetically unique, clustering in a single clade. Substitutions in the pre-membrane (prM) and nonstructural genes NS2A and NS4A correlated with the attenuation of the Tongan viruses and suggest that genetic change may play a significant role in dengue epidemic severity.