Version May 2024
INTRODUCTION — The region of Australia, New Zealand, and the southwestern Pacific (Oceania) encompasses a remarkable diversity of geography, racial groups, cultures, technologic sophistication, and political systems. With the exception of New Zealand and the southern temperate parts of Australia, all of the nations and territories of Oceania lie within the tropics. The region may be divided into three subdivisions; there is considerable overlap between these areas (figure 1 and figure 2).
●Temperate Australia and New Zealand – Most Australians live in coastal temperate regions with sophisticated medical services with good communications. This is also the case for both the North and South Islands of New Zealand.
●Tropical and central Australia – The center of the continent and areas north of the tropic of Capricorn, called the "far north," are sparsely populated. There are large distances between population centers, and travel routes often pass through relatively inhospitable country. This is a unique environment with distinct patterns of disease and fairly basic medical services [1].
●Oceania – Oceania includes the following countries in the southwest Pacific: Cook Islands, Fiji, Guam, Kiribati, Marshall Islands, Nauru, New Caledonia, Niue, Northern Mariana Islands, Palau, Papua New Guinea, Pitcairn Islands, Samoa, American Samoa, Solomon Islands, Tahiti, Tokelau, Tonga, Tuvalu, Vanuatu, United States Trust Territory of the Pacific Islands, Wake Island, Wallis, and Futuna. Centers with busy tourist traffic often have adequate medical services, but many communities have only rudimentary services and are separated by long distances with irregular transport. Remoteness, poverty, and tropical climate all contribute to vulnerability to and significant burden of infectious diseases in this region [2].
Issues related to travel to Australia, New Zealand, and the southwestern Pacific will be reviewed here.
TEMPERATE AUSTRALIA AND NEW ZEALAND — The important syndromes that can be acquired in this region are outlined in the table (table 1). The risks of travelers' diarrhea, viral respiratory illness, food poisoning, and common community illnesses are similar to those in developed countries in other parts of the world. Outbreaks of viral gastroenteritis, hepatitis A virus, and salmonellosis occur infrequently, and urban water supplies are usually safe. In New Zealand, the consumption of raw shellfish collected from areas where human effluent contamination may have occurred, such as marinas, should be avoided, as outbreaks of gastrointestinal illnesses such as shigellosis have been reported [3]. Rates of campylobacteriosis have declined dramatically in New Zealand following the introduction of a range of voluntary and regulatory interventions to reduce Campylobacter spp contamination of poultry in the mid-2000s [4]. Outbreaks of vaccine-preventable diseases such as measles occur infrequently [5].
Tourists frequently travel in this region on cruise ships. The presence of large numbers of people in close proximity facilitates person-to-person disease transmission; outbreaks of respiratory (eg, COVID-19, influenza) and gastrointestinal (eg, noroviruses) illness can occur [6]. Appropriate immunizations and frequent hand washing are important preventive measures [7].
Arboviral infections — Ross River virus (RRV) is the most common arboviral infection in temperate Australia [8-11] (see "Ross River virus infection"). It is an alphavirus transmitted by mosquitoes of the Aedes, Ochlerotatus, and Culex species and is endemic in all of Australia including Tasmania [8], with frequent outbreaks typically occurring in the months of summer and autumn (December to April). RRV causes an acute febrile illness and rubella-like rash followed by a polyarthropathy and constitutional symptoms (such as fatigue) that may be debilitating and last for many months. Barmah Forest virus (BFV) has a similar epidemiology and causes a similar, albeit typically less severe, illness to RRV. Arthritis tends to be more common and prominent in RRV, while rash is often more common and florid in BFV infection [8].
Other arboviruses are uncommon in temperate Australia, and there are none of medical importance in New Zealand [12]. However, an outbreak of Japanese encephalitis (JE) primarily affecting residents of the Murray River region in south-eastern Australia occurred during the 2021 to 2022 and 2022 to 2023 summer seasons, with potential ongoing risk [13].
Rickettsial infections — Australian (Queensland) tick typhus is the most common rickettsial disease in Australia and occurs almost all the way down the east coast [14-16]. It is caused by Rickettsia australis and transmitted by Ixodes ticks. Native rats and bandicoots are the vertebrate hosts. It usually causes a mild illness with the acute onset of fever, myalgia, and headache, usually followed by the development of a maculopapular rash within up to 12 days. Occasionally, the rash is petechial or vesicular. There is usually localized tender lymphadenopathy, and careful inspection may reveal a small eschar at the site of the tick bite. Evidence demonstrates an increasing disease burden and a broad spectrum of clinical presentations, with increased recognition of severe disease, including death [14]. Campers and coastal bushwalkers are especially at risk. Infection can occur year-round, but seasonal variation is described with most cases occurring in winter and spring (June to November), coinciding with increasing tick densities [14].
Other rickettsial infections are less common:
●Flinders Island tick typhus (Rickettsia honei) was first recognized on islands in Bass Strait and causes a relatively mild illness, with symptoms such as fever, myalgia, headache, and rash. Cases typically occur over the summer months (December to January) [17]. R. honei is clinically and serologically similar to R. australis and is endemic to southeastern Australia [18]. The reptile tick vector is Bothriocroton (Aponomona) hydrosauri [19]. Blue tongue lizards and snakes are the vertebrate host.
●Scrub typhus, caused by Orientia tsutsugamushi, is a relatively severe illness that occurs in areas of northern (tropical) Australia (see below) [18,20,21]. It is transmitted by mites; bandicoots and rats are the vertebrate host. (See "Scrub typhus", section on 'Transmission'.)
●Murine typhus (Rickettsia typhi) is endemic in subtropical and temperate areas of Australia [22] and the north island of New Zealand [18,23]. Transmission is by fleas; rodents are the vertebrate host. Contact with rodents is the most important risk factor for disease. (See "Murine typhus".)
Human ehrlichiosis has not been reported in Australia or New Zealand.
Leptospirosis — Leptospirosis is endemic in parts of eastern rural Australia and New Zealand; these areas have some of the highest reported incidence rates among resource-abundant settings [24,25].
Traditionally leptospirosis in developed countries has been an occupationally acquired disease in livestock and agricultural workers, but infection through recreational exposure may also occur [26,27]. The most common occupational infection is due to Leptospira borgpetersenii serovar hardjo associated with the dairy and beef industries. Outbreaks can be linked to extreme weather events and floods [28]. Travelers should be advised to avoid swimming in rivers and waterfalls after heavy rainfall [26].
Recreational exposures and flooding events are increasingly recognized as important sources of transmission [25]. Tourists may be at risk through "farm stay" establishments and through freshwater exposure as white water rafters, canoeists, and hikers.
The clinical pattern is that of an acute flu-like illness, often accompanied by aseptic meningitis. Occasionally, leptospirosis causes severe respiratory distress [29]. (See "Leptospirosis: Epidemiology, microbiology, clinical manifestations, and diagnosis".)
Cryptosporidiosis — Cryptosporidiosis is a common cause of diarrheal disease in New Zealand and Australia. Outbreaks have been linked person-to-person transmission, as well as to contact with farm environments, consumption of contaminated water and food, and recreational water exposures (eg, swimming pools) [30,31]. Reports of illness typically peak in the summer and autumn months.
Other infections — Several other infections occur infrequently among travelers to this region.
●Q fever occurs widely in Australia [32] but is mainly associated with the livestock and meat industries and rarely affects travelers. Infection can occur in the absence of high-risk activities [33-35]. Q fever does not occur in New Zealand [36,37].
●Zoonotic brucellosis occurs in Australia; most cases result from Brucella suis following contact with feral pigs [38]. In Queensland, hunting feral pigs is a recreational and tourist activity, with slaughtering of pigs in the field [39]. Cases have also been reported in the Northern Territory and northern New South Wales. A case of pig-associated brucellosis was reported in New Zealand, but further investigation has found that the isolate was related to a marine isolate of Brucella [40]. New Zealand livestock remains free of zoonotic Brucella [41]. (See "Brucellosis: Epidemiology, microbiology, clinical manifestations, and diagnosis".)
●Psittacosis occurs in southern Australian states with occasional outbreaks. (See "Psittacosis".)
●Uncommonly, Mycobacterium ulcerans causes localized chronic progressive skin ulceration; the risk to travelers is small. Historically, infections have been predominantly reported from coastal areas in southern Victoria between Gippsland and the Bellarine peninsula and from Queensland near Cairns and Rockhampton. More recently, reported cases have been increasing in southeastern Victoria and spreading into new geographic areas including the Mornington Peninsula [42]. (See "Buruli ulcer (Mycobacterium ulcerans infection)".)
●Angiostrongylus cantonensis (rat lung worm) may cause encephalitis meningitis and meningoencephalitis following ingestion of the intermediate host, a slug or snail, which contains second- or third-stage larvae [43]. Its geographic reach has extended to Sydney and northern New South Wales [43,44]. The incubation period is 1 to 36 days, and disease is more severe in children. Most cases are self-limited, but death may result from massive infection. (See "Eosinophilic meningitis", section on 'Angiostrongylus cantonensis'.)
●Toxocara infection follows ingestion of infective eggs. Toxocara canis is common among stray dogs and cats but is infrequently detected in Melbourne parks [45] or Perth beaches [46]. The rate of ocular toxocariasis is low. (See "Toxocariasis: Visceral and ocular larva migrans".)
●Ancylostoma caninum is common in Australian dogs, and infrequent human infection is seasonal and manifest as enteritis. (See "Eosinophilic gastrointestinal diseases".)
●Fasciola hepatica is found in sheep and cattle in southeastern Australia (including Victoria, New South Wales, southern Queensland, and Tasmania), with rare human cases reported [47].
●Corynebacterium diphtheriae (toxigenic and nontoxigenic strains) have been associated with cutaneous infections in residents of, and travellers to, northern Australia [48-50]. Infections are often polymicrobial, with S. aureus and S. pyogenes common co-pathogens.
Envenomations and bites
Snakes — Australia and Papua New Guinea are host to a variety of venomous snakes [51]. The most commonly encountered species are timid and will not become aggressive unless surprised or pursued. Travelers to rural and wilderness areas should treat all snakes with respect, use appropriate footwear, and have some knowledge about first aid measures for snakebite, including the principle of immobilizing a bitten limb. Antivenom is generally available at regional hospitals. (See "Snakebites worldwide: Management".)
Spiders — There are several venomous spiders; these include the Redback, which is common but the bite is rarely fatal, and the Sydney funnel-web, which is very limited in distribution. Antivenoms are available [52]. (See "Diagnostic approach to the patient with a suspected spider bite: An overview".)
Ticks — In addition to tick-borne infection, human tick paralysis due to Ixodes holocyclus is occasionally reported, especially along the Australian east coast [53]. Antitoxin is also available (see 'Rickettsial infections' above).
Infrequently, serious tick-induced allergies, including mammalian meat allergy and tick anaphylaxis, may follow tick bites [54]. (See "Allergy to meats", section on 'The role of ticks in red meat allergy'.)
Sea creatures — Sting rays, sharks, and jellyfish may cause injury to swimmers and waders in summer months. The blue-ringed octopus (Hapalochlaena maculosa) is found in Papua New Guinea and all around Australia; it lives in rock pools and around shallow reefs and can change color to match its surroundings [55]. The creature is small enough to fit into the palm of a hand and displays vivid blue rings on its skin, especially when agitated. As such, it is attractive to both curious children and adult tourists alike. The venomous bite is initially thought to be trivial; symptoms begin within 10 to 20 minutes, including paresthesias, muscular weakness, vomiting, and respiratory arrest. (See "Marine envenomations from corals, sea urchins, fish, or stingrays" and "Jellyfish stings".)
Sandflies and midges — Sandfly and midge bites cause local induration and may become secondarily infected. They are a special problem in the coastal regions of parts of New Zealand and Australia.
Environmental factors — For most of the year, the climate in temperate Australia and New Zealand is comfortable, but the summer sun can be particularly intense and precautions should be taken to prevent sunburn. Drowning deaths, especially at beaches, have been reported amongst international travelers to Australia; travelers should be aware of limitations in swimming ability and recognize differences in beach conditions between their home country and Australia [56].
TROPICAL AND CENTRAL AUSTRALIA — In addition to the infections and other health hazards mentioned above, risks for the traveler in a tropical climate include insect bites (which may become secondarily infected) and dermatophytoses. Travelers are discouraged from going outdoors in bare feet. Hookworm is endemic in some communities.
Arboviral infections — Dengue is not endemic in Australia, but competent mosquito vectors are present in the Torres Strait (Aedes albopictus) [11,57] and Northern Queensland (Aedes aegypti) [58]. Intermittent dengue outbreaks with local transmission have occurred following introduction by infected travelers. Outbreaks of serotypes 1, 2, and 3 have been reported, although hemorrhagic fever is rare. The peak incidence is in summer and autumn, which are associated with travel and importation of infection from neighboring countries as well as increased rain and humidity leading to increased mosquito breeding cycles [58]. The risk of dengue in Northern Queensland has diminished substantially, likely as a result of the Wolbachia/World mosquito program [59]. Aedes spp mosquitoes tend to also bite in the daytime; as a result, 24-hour mosquito protection measures are recommended. (See "Dengue virus infection: Epidemiology".)
Japanese encephalitis has been reported on the Australian mainland [60], and it has also been a problem on the Torres Strait Islands [61,62]. In 2021 to 2022, cases were reported for the first time in the Top End of the Northern Territory, as well as across parts of south-eastern Australia [13].
Other important arboviruses in the region include Ross River virus (see "Ross River virus infection"), Barmah Forest virus, Kunjin virus (closely related to West Nile virus), and Murray Valley Encephalitis Virus (MVEV; previously known as Australian encephalitis). MVEV is enzootic in the far north of Australia and causes infrequent outbreaks in southern states, including in 2022 to 2023 [9,63,64]. MVEV infections with poor outcomes have been reported in travelers to northern Australia [65].
Chikungunya virus infection is widespread throughout the Pacific [66]. Imported cases have been reported in Australia [67] and New Zealand [68]. Distribution of competent Chikungunya virus mosquito vectors (Aedes spp) is limited to northern Queensland in the Torres Strait; travelers to these areas should take measures to avoid mosquito bites. (See "Chikungunya fever: Epidemiology, clinical manifestations, and diagnosis".)
Imported cases of Zika virus have been reported in Australia and New Zealand [68-71] (see "Zika virus infection: An overview"). Distribution of competent Zika virus vectors (Aedes spp) is restricted to north Queensland and the Torres Strait, and these regions remains receptive to Zika virus introduction [72]. Travelers to these areas should take measures to avoid mosquito bites.
Rickettsial infections — Australian (Queensland) tick typhus and scrub typhus are the most important tick-borne diseases in northern Australia. Scrub typhus has an unusual pattern of distribution with regional foci of high risk, including northern Queensland, the Torres Strait Islands, areas of the Top End of the Northern Territory, and the Kimberley region of Western Australia; all are areas that receive high levels of annual rainfall [18,73]. Outdoor activities such as hiking and camping in mite habitats (eg, forests and secondary vegetation) increase the risk of exposure and infection [18]. Queensland tick typhus is found along most of the Australian East Coast and includes coastal or near coastal regions in Northern Queensland and the Torres Strait Islands [18]. Murine typhus is also considered to be endemic [18], and Q fever also occurs in the region.
Melioidosis — Melioidosis, caused by the soil saprophyte Burkholderia pseudomallei, is endemic to the Northern Territory, far north Queensland, and northern Western Australia [74]. It is an important cause of severe community-acquired pneumonia in the far north of Australia. Infection in travelers has occurred, and the risk is highest during the wet season (November through April). The disease range is expanding, with cases reported in Southern Queensland during La Niña weather events [75]. Risk factors include diabetes mellitus, alcohol use, chronic lung disease, and chronic renal disease [76].
The clinical manifestations of melioidosis may not appear for many years after the traveler leaves the endemic area. Common presentations include fulminant pneumonia, skin and soft tissue abscesses, bacteremia, and genitourinary infection, including prostatic abscesses [77]. Less common presentations include osteomyelitis, septic arthritis, visceral abscesses, and a range of neurological presentations including meningoencephalitis, myelitis, meningitis, and epidural abscess [77]. It may also present as subacute or chronic pneumonia, causing cavitary apical disease that mimics tuberculosis. Awareness of possible melioidosis in travelers is particularly important because there may be a need for urgent empiric therapy before the microbiologic diagnosis is confirmed. (See "Melioidosis: Epidemiology, clinical manifestations, and diagnosis".)
Other infections — Eosinophilic meningitis due to A. cantonensis occurs along the Queensland coast [78]. (See "Eosinophilic meningitis", section on 'Angiostrongylus cantonensis'.)
Several cases of Hendra virus infection have been described [79-82]; pneumonic and encephalitic forms are associated with high mortality. There is a strong epidemiological association with horses, with reported cases occurring in veterinarians and horse trainers; the risk for travelers is low. (See "Nipah, Hendra, and other henipaviruses".)
Brucellosis, due to B. suis, is most commonly acquired in northern Queensland and mainly occurs in people who hunt wild pigs. (See "Brucellosis: Epidemiology, microbiology, clinical manifestations, and diagnosis".)
There have been three reported cases of fatal encephalitis due to Australian bat lyssavirus (ABLV) in Queensland [79,83]. ABLV is regarded as endemic in Australian insectivorous and fruit bats; handling of wild bats by visitors is strongly discouraged. The prevalence of this virus in the wild bat population is low (<1 percent); in sick, injured, or orphaned bats, the prevalence is 5 to 10 percent [84]. Therefore, postexposure prophylaxis with vaccine and rabies immune globulin is offered to all individuals with bat scratches or bites. Travelers should avoid contact with bats and seek medical attention following being scratched or bitten by a wild bat. (See "Rabies immune globulin and vaccine".)
Strongyloides stercoralis is a soil-transmitted helminth. It is present in rural and remote regions of Australia, in particular Queensland, Northern Territories, Western Australia, northern South Australia, and northern areas of New South Wales. Rates are highest in native Australians; the risk is low for travelers. However, travelers should avoid going barefoot in these regions [85]. (See "Strongyloidiasis".)
Australia, New Zealand, and Oceania are free of human schistosomiasis and yellow fever.
Envenomations and bites
Snakes — Snakes of the tropical region include the Western Brown Snake, the Death Adder, and the Taipan, one of the most dangerous in the world [51]. Sea snakes are common in the waters off tropical Australian and the Pacific nations; they are moderately venomous but their bite is rarely fatal. (See "Snakebites worldwide: Clinical manifestations and diagnosis".)
Crocodiles — In most of northern Australia, swimming in coastal estuaries and rivers carries the risk of crocodile attack. Appropriate caution is advised.
Sea creatures — Of all jellyfish (Coelenterata) inhabiting the coastal waters of northern Australia, the box jellyfish (Chironex fleckeri) is probably the most dangerous. Waders and swimmers may run into the tentacles in shallow water from October through May [86]. Severe local pain may be followed by apnea and cardiac arrest, sometimes in less than five minutes. Prompt first aid with CPR and administration of antivenom may be lifesaving. (See "Jellyfish stings".)
Other venomous jellyfish include the bluebottle (Physalia utriculus), Portuguese man-o'-war (Physalia physalis), and the Irukandji (Carukia barnesi) [86]. Stone fish, cone shells, sting rays, and various spiny reef creatures also occasionally cause injury to unwary visitors, especially those without proper footwear.
Environmental factors — Travelers to central and northern Australia should be aware that distances are vast, roads may be difficult, temperatures are often severe, and water sparse. Each year, individuals perish in the "outback" despite all efforts to warn travelers of the potential hazards and to encourage proper planning [87]. Furthermore, sophisticated medical care may not always be available outside the main cities.
OCEANIA — A variety of different types of infections can occur in travelers to Oceania. Food- and water-borne infections usually predominate. Routine childhood vaccination uptake by the local populations may be poor, with major consequences locally, but also exposing unvaccinated travelers to vaccine-preventable diseases. Infected locals may transmit infection when traveling overseas; this was illustrated by a large measles outbreak in Samoa and Tonga in late 2019 [88].
Travelers' diarrhea is a common problem, and most cases are presumably due to enteropathogenic Escherichia coli. Other enteric pathogens include Shigella, Salmonella, and Entamoeba histolytica, and outbreaks of viral gastroenteritis occur from time to time. Enteric fever, due to Salmonella Paratyphi A or Salmonella Typhi, is sometimes seen. Penicillin-resistant Streptococcus pneumoniae is prevalent in Papua New Guinea; this should be taken into account when travelers develop pneumonia or meningitis.
Hepatitis A is endemic throughout most of Oceania, with an estimated average age of infection in middle childhood [89]. Periodic outbreaks are reported [90-92]. Hepatitis B is endemic throughout the Western Pacific region [93]. There are also high levels of sexually transmitted infections. Papua New Guinea has the highest prevalence of HIV infection [94].
Typhoid is endemic throughout most of Oceania, with Pacific island nations including Fiji, Nauru, Samoa, and Papua New Guinea reporting high case counts of typhoid fever and frequent large outbreaks of the disease [95-99]. Cases of typhoid have been reported in travelers returning from Pacific Island nations [100].
Tuberculosis (TB) is endemic throughout the region, with incidence rates in Kiribati, the Marshall Islands, Nauru, Papua New Guinea, and Tuvalu falling into the highest risk category (>100 per 100,000 population) [101]. Papua New Guinea is a high-burden country for multidrug resistant (MDR)-TB, and high rates of HIV-associated TB are also documented [101]. Overall risk to travelers is low, and acquisition is mainly seen in those undertaking extended stays, although infection is possible even with brief or unrecognized exposure [102]. Additional TB-related precautions should be considered in those planning extended stays, children aged under five, or those at increased risk of progression to active disease such as immunocompromised travelers (especially HIV-infected and those receiving anti-tumor necrosis factor-alpha inhibitor therapy) [102].
Hookworm is endemic in many areas, with most cases concentrated in Papua New Guinea, followed by Fiji, the Solomon Islands, and Vanuatu [103]. Strongyloidiasis is an important infection in the region (especially in Papua New Guinea), but overall prevalence data are lacking [103,104]. Travelers should avoid going barefoot. Ascariasis and trichuriasis cases are also present in significant numbers. Tropical skin infections may cause considerable morbidity and distress.
Lymphatic filariasis (LF) is reported throughout the region. Many countries previously endemic for the disease, including Cook Islands, Niue, Vanuatu, Kiribati, Marshall Islands, Palau, Tonga, and Wallis and Futuna have been validated as having eliminated LF as a public health problem [105-107]. However, ongoing foci of transmission are reported, with most of the people at risk being in PNG [105,106]. Elimination efforts, including mass drug administration, are continuing in Papua New Guinea, Fiji, French Polynesia, New Caledonia, Samoa, American Samoa, and Tuvalu [107]. Cases have been reported in travelers [108], so travelers are advised to use mosquito protection measures.
Haemophilus ducreyi has been recognized as an important cause of chronic skin ulceration in predominantly children in Samoa, Papua New Guinea, and the Solomon Islands [109-111]. (See "Chancroid".)
Corynebacterium diphtheriae (toxigenic and nontoxigenic strains) have been associated with cutaneous infections in travelers to Samoa and other Pacific Islands [112-114].
Papua New Guinea and the Pacific Islands are considered to be free of terrestrial (canine) rabies, but risk of lyssavirus from bats exists and is presumed to have widespread distribution [115].
Tourists commonly visit the region on cruise ships. As such, large groups of people are living in a confined space, and person-to-person transmission of respiratory and gastrointestinal (eg, noroviruses) illness is a particular risk [7]. Appropriate immunizations and frequent hand washing are important preventive measures [7].
Malaria — Malaria is endemic in Papua New Guinea, the Solomon Islands, and Vanuatu [116] and is an important risk for travelers to these areas. Papua New Guinea has the highest malaria burden, accounting for almost 87 percent of cases in the World Health Organization Western Pacific Region. The number of cases continues to increase in both Papua New Guinea and the Solomon Islands, while the number cases in Vanuatu has been decreasing since 2018 [117]. The proportion of cases caused by Plasmodium vivax increased between 2000 and 2020 from 17 to 30 percent [117]. Plasmodium falciparum chloroquine resistance is widespread, and chloroquine is no longer recommended as a first-line treatment for P. vivax acquired in Oceania due to high rates of treatment failure [117,118]. (See "Treatment of uncomplicated falciparum malaria in nonpregnant adults and children" and "Non-falciparum malaria: P. vivax, P. ovale, and P. malariae".)
Issues related to prevention of malaria in travelers are discussed separately. (See "Prevention of malaria infection in travelers".)
Arboviral infections — Tropical islands, including those in Oceania, have experienced an increasing number of arbovirus outbreaks over the past decade. Factors facilitating spread to susceptible populations include the presence of competent vectors (eg, A. aegypti, A. albopictus, and other endemic Aedes mosquito species), natural disasters such as severe weather events, the lack of safe water supplies, sanitation, limited local resources for vector control, and increasing travel between the islands [119,120].
Dengue is hyperendemic in Papua New Guinea [121] and has been reported throughout most of Oceania, notably Fiji, the Marshall Islands, the Federated States of Micronesia, Palau, and Vanuatu [122-125]. Outbreaks occur throughout the region and are increasing in frequency and scale [126]. Variability in surveillance and reporting capabilities mean that reported cases likely underestimate actual case numbers, and travelers are at risk of infection, especially during the rainy season. (See "Dengue virus infection: Clinical manifestations and diagnosis".)
Ross River virus causes epidemics in most parts of the region [127-129]. Murray Valley and Japanese encephalitis have been mainly confined to Papua New Guinea and the Torres Strait Islands [9,122]. (See "Ross River virus infection".)
Chikungunya reached the Western Pacific Islands in 2011; the first outbreak was reported in New Caledonia [130]. Subsequent outbreaks and importations were reported in 2012 in Papua New Guinea, in 2013 in the Federated States of Micronesia, and in 2014 to 2015 in American Samoa, the Cook Islands, French Polynesia, Kiribati, Samoa, Tonga, and Tokelau [130]; since then, it has spread throughout the Pacific [131]. The vectors are A. aegypti and A. albopictus (Asian tiger mosquito). Symptoms include high fever, rash, arthralgia, myalgia, emesis, and severe nausea, and many patients experienced lingering arthralgia. (See "Chikungunya fever: Epidemiology, clinical manifestations, and diagnosis".)
The first Pacific outbreak of Zika virus was reported on Yap Island in 2007. In 2013, an outbreak was reported in French Polynesia affecting about 11 percent of the population with subsequent spread to the Cook Islands and Easter Island [132]. By late 2015, it had spread across the rest of the Pacific [133]. Zika virus is discussed further separately. (See "Zika virus infection: An overview".)
Rickettsial infections — Scrub typhus has been reported in Papua New Guinea, the Solomon Islands, northern Vanuatu, and Palau [18]. It is likely that scrub typhus and other rickettsial infections are under-recognized causes of potentially serious acute febrile illness due to poor access to advanced diagnostic facilities [18].
Eosinophilic meningitis — Infection due to A. cantonensis (the rat lungworm) is an increasing problem for visitors to Oceania [78,134], particularly backpackers, surfers, and scuba divers who are less likely to be staying in Western hotel–style accommodations. It can be acquired by eating contaminated leafy vegetables (in salads), infected snails and slugs, and land crabs. One to three weeks later, dermatomal sensory paresthesias may herald the onset of meningitis. Motor symptoms are uncommon. (See "Eosinophilic meningitis".)
Other infections
●Leptospirosis – The islands of the southwest Pacific have environmental conditions that are highly favorable for leptospirosis transmission. Outbreaks of leptospirosis are often related to flooding [135]. Leptospirosis is an important cause of acute febrile illness throughout the southwest Pacific, and the infection has been reported from most Pacific islands, including Fiji, New Caledonia, Vanuatu, and French Polynesia [136]. Travelers engaging in activities that involve contact with freshwater, soil, and animals are at risk of exposure, and infections in travelers have been reported [25,137]. The disease may be severe with hepatic and renal involvement; sometimes pulmonary hemorrhage is a prominent feature [138]. (See "Leptospirosis: Epidemiology, microbiology, clinical manifestations, and diagnosis".)
●Cryptococcal disease – In Papua New Guinea and Australia, Cryptococcus gattii infection occurs relatively more frequently than Cryptococcus neoformans and is often associated with cryptococcoma [139]. (See "Cryptococcus gattii infection: Microbiology, epidemiology, and pathogenesis".)
●Melioidosis – Melioidosis has been reported in Guam, Papua New Guinea, New Caledonia and Micronesia; it presumably exists in other areas in the southwest Pacific but is probably underrecognized in some countries due to limited laboratory facilities [140,141]. (See "Melioidosis: Epidemiology, clinical manifestations, and diagnosis".)
●Coral injury – Local injury due to coral-related trauma may quickly become infected with marine or terrestrial bacteria. These infections often progress despite treatment with antibiotics because "coral slime," a proteinaceous material, is introduced into the wound and acts as a foreign body [142]. Any significant laceration sustained from coral should be carefully debrided and scrubbed with a brush; an anesthetic may be required. If infection does become established, it is unlike to resolve without scrubbing.
●Brucellosis – Brucellosis caused by B. suis is endemic in some parts of Oceania, including Wallis and Fortuna Islands and Tonga. Infection is usually acquired during the butchering of wild pigs [143]. (See "Brucellosis: Epidemiology, microbiology, clinical manifestations, and diagnosis".)
Envenomations, toxins, and bites
Snakes and sea creatures — Papua New Guinea has several venomous snakes, including the Taipan. Sea snakes and other venomous marine risks are similar to those in tropical Australia. A major concern is lack of locally available antivenoms, even in major centers [144]. (See "Snakebites worldwide: Management".)
Fish poisoning — There are two common types of fish poisoning in the region [145,146]. Scombroid fish poisoning is due to decomposition of certain fish resulting in accumulation of histamine and related substances in the flesh [147]. Symptoms begin soon after ingestion and consist of paresthesia around the mouth and abdominal pain followed by vomiting and diarrhea. Some patients have flushing, headache, urticaria, and wheeze. The illness is usually self-limited and settles in a few hours. (See "Scombroid (histamine) poisoning".)
Ciguatera fish poisoning occurs in the southwestern Pacific (especially Kiribati, Tuvalu, French Polynesia, Vanuatu, and Cook Islands), Queensland, and the Gulf of Carpentaria, although fish are sometimes transported large distances to be served in restaurants [148,149]. The fish responsible are at the top of the food chain and include cod, sturgeon fish, parrotfish, red bass, Spanish mackerel, and barracuda. The toxin comes from dinoflagellates and binds to sodium channels, causing depolarization with acute diarrhea and abdominal pain, lasting two to four days. Subsequent neurologic symptoms include myalgia, paradoxical "burning" of skin on contact with cold water, paresthesias, and a mood disorder lasting weeks to months. (See "Ciguatera fish poisoning".)
Environmental factors — Many regions, especially in Papua New Guinea, are remote with few roads and poor access to medical facilities. Travelers to the southwestern Pacific should also be aware of the monsoonal nature of the weather and plan their travel accordingly.
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Travel medicine".)
INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, “The Basics” and “Beyond the Basics.” The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on “patient info” and the keyword(s) of interest.)
●Basics topics (see "Patient education: Vaccines for travel (The Basics)")
●Beyond the Basics topics (see "Patient education: General travel advice (Beyond the Basics)")
SUMMARY
●Australia, New Zealand, and Oceania are relatively safe destinations for tourists and business travelers. Individuals planning to spend more than two weeks in the region should make themselves aware of the likely risks, especially when visiting remote areas.
●Unique infections include Ross River virus, Australian (Queensland) tick typhus, Murray Valley Encephalitis virus (Australian encephalitis), and melioidosis. Risk for envenomations and bites varies by region.
●Insect repellent is essential. Apparel should include protection from the sun and appropriate footwear. Precautions should be observed with food and water, especially when camping or in remote communities.
●Antimalarial prophylaxis should be prescribed according to published guidelines. Specific travel vaccines are not necessary for temperate Australia and New Zealand. Routine vaccinations including tetanus and poliomyelitis status should be up to date.
●Hepatitis A and B virus and typhoid vaccination should be considered for travelers to Oceania, especially when visitors are staying in village-type accommodation. These vaccines are not relevant for travelers to New Zealand and Australia. Japanese encephalitis vaccine should be considered for travelers visiting endemic areas of Papua New Guinea and the Torres Strait Islands.
ACKNOWLEDGEMENT — The UpToDate editorial staff acknowledges Malcolm McDonald, PhD, FRACP, FRCPA, who contributed to an earlier version of this topic review.
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