Australia, one of the WHO founders, participated in the International Health Conference in 1946, which resutled in the drafting of the WHO constitution, turning over the functions of the Office International d'Hygiene Publique (OIHP) to WHO and setting up of an Interim Commision to prepare for the First World Health Assembly. It joined the WHO on 2 February 1948. The WHO Representative Office in the South Pacific was established on 13 June 1956 in Sydney, Australia before it was transferred to Suva, Fiji in 1965.

Brunei Darussalam was under the rule of the United Kingdom of Great Britain and the Northern Ireland before joining WHO in May 1953. At the Sixth World Health Assembly, Brunei Darussalam was assigned to the Western Pacific Region as an area, ''without prejudice to any questions regarding sovereignty''. On 1 January 1984, it gained its full independence and sovereignty from the United Kingdom, and on 25 March 1985, Brunei Darussalam joined WHO as a Member State. Brunei Darussalam was covered by the WHO Representative Office in Singapore from May 1956 until 1964 when the WHO Rerepesentative Office was transferred to Kuala Lumpur, Malaysia.

The General Population Census of 2008 put Cambodia’s population at 13.4 million by March 2008. The population density is 75 per square kilometre. The male-to-female ratio is gradually normalizing after the distortions caused by 30 years of war during the last century. The average household size is 4.7 people, with 80% of the population living in rural areas. The median age in 2008 was 21 years, about four years more than in 1998.

China, one of the founders of WHO, participated in the International Health Conference in 1946, which resutled in the drafting of the WHO constitution, turning over the functions of the Office International d'Hygiene Publique (OIHP) to WHO and setting up of an Interim Commision to prepare for the First World Health Assembly. It joined the WHO on 22 July 1946.

In May 1953, before its independence, Cook Islands was assigned to the Western Pacific Region at the Sixth World Health Assembly ''without prejudice to any questions regarding sovereignty'' as an area. On 4 August 1965, it became a self-governing territory in free association with New Zealand. It joined the World Health Organization on 9 May 1984 as a Member State followed by the establishment of its Ministry of Foreign Affairs in 1983. The WHO Representative Office in the South Pacific covered Cook Islands from 1956 to 1986, when the WHO Representative Office in Samoa was established to cover the American Samoa, Cook Islands, Niue, Samoa and Tokelau.

Fiji has the largest population of all the South Pacific island countries, with an estimated 2010 population of 854 000: 433 000 males and 421 000 females. The average annual growth rate stands at 0.8%, the slow growth being due to a moderately low level of fertility and a high level of emigration. Fiji’s Economic Exclusive Zone contains 332 islands covering a total land area of 18 333 square kilometres in 1.3 million square kilometres of the South Pacific Ocean. The population occupies around one-third of the 332 islands and is concentrated on the two largest, Viti Levu (10 429 square kilometres) and Vanua Levu (5556 square kilometres), with the nation's capital, Suva, located on Viti Levu. People in Fiji are living longer, with life expectancy standing at 68 years for males and 72 years for females.

French Polynesia is a French territorial overseas community comprising 35 volcanic islands and about 183 low-lying coral atolls. It covers 4167 million square kilometres in the South Pacific Ocean, with a land area of 3521 square kilometres. The population was estimated to be 280 000 in 2014. French Polynesia is divided into five administrative units: Austral Islands, Windward Islands, Marquesas Islands, Leeward Islands and Tuamotu-Gambier.

Guam is an unincorporated and organized territory of the United States of America in the western Pacific Ocean. It has an estimated population of 162 000 spread across 19 villages, the majority of which live in the northern part of the island.

In May 1953, Hong Kong (China), formerly Hong Kong SAR, China, was assigned to the Western Pacific Region at the Sixth World Health Assembly ''without prejudice to any questions regarding its sovereignty'' as an area. It was under the British administration until 30 June 1997. From the fortieth session of the Regional Committee in 1989 to the forty-seventh in 1996, Hong Kong attended sessions of the Regional Committee under its own name. With effect from the forty-eighth session in 1997, Hong Kong has attended the Regional Committee as Hong Kong SAR (China). The Regional Office was placed temporarily in Hong Kong (China) from August 1950 to July 1951. Hong Kong (China) was covered by the WHO Representative Office in Taipei, China (Taiwan) from 1959 until it was closed on 30 June 1972. In 1972, the responsibility over Hong Kong was transferred to the Western Pacific Regional Office under the Office of the Director, Programme Management.

Japan joined WHO on 16 May 1951. It was covered by the WHO Representative Office in Taipei, China (Taiwan) from 1959 until the Office closed on 30 June 1972. Since then the responsibility over Japan was transferred to the Western Pacific Region under the Office of the Director, Programme Management.

The Republic of Kiribati, located in the Pacific, consists of 32 low-lying atolls and one volcanic island in three main groups, the Gilbert, Phoenix and Line Islands. The country spreads over 3.5. million kilometres of ocean, but has a total land area of only 811 square kilometres.

The Lao People’s Democratic Republic was projected to have a population of 6.1 million in 2009, based on the 1995-2005 population growth rate of 2.1%. It has a sparse population density (26 per square kilometre) with large interprovincial variations, and an average household size of 5.9 persons. The topography breaks into lowland areas along the Mekong River that depend predominantly on paddy rice, and highland areas that depend on upland rice and the gathering of non-timber forest products for a livelihood. The population is young, but there are signs of changes in the demographic structure: the percentage of the population under 15 years of age decreased from 43.6% to 37.9% between 1995 and 2009. The nation is rural, with the beginnings of a rural-to-urban shift, as indicated by the increase in urban areas: the estimated percentage of the population living in rural areas decreased from 72.9% to 66.8% between 2005 and 2010.

Malaysia joined WHO on 24 April 1958 as Malaya. In 1957, it obtained its independence. In 1963, Malaysia was formed with Singapore, North Borneo and Sarawak. In 1965, Singapore withdrew from the Federation. From May 1956 to January 1964, the WHO Representative Office in Singapore covered Brunei Darussalam, Malaysia and Singapore. In 1964, the Representative Office was transferred to Kuala Lumpur, Malaysia.

The Marshall Islands covers an area of 181 square kilometers in the Pacific Ocean and is comprised of 29 atolls and five major islands. The Marshall Islands are governed by a President elected from among members of the Marshallese Congress and a legislature elected through popular vote. Major economic activities in the Marshall Islands include agriculture, copra, tuna processing and tourism. The United States Government provides direct aid to the Marshall Islands. Government assistance from the United States of America is the mainstay of the economy. Current surveys and socioeconomic indicators suggest that poverty and hardship are on the rise.

The Federated States of Micronesia contains 607 volcanic islands and atolls scattered over 1 million square miles of the Pacific Ocean. The land area totals 704.6 square kilometres, with 7192 square kilometres of lagoon area. Based on the preliminary results of the 2010 Census, the Federated States of Micronesia has a population of 102 624, 35.7% below 15 years old, and 3.3% 65 years and over. The average age of the population is estimated to be 21.5 years, and for every 100 females, there are about 103 males. There has been a decrease in the population due to substantial outmigration over the past decade. Approximately 49% of the population lives in Chuuk, 32% in Pohnpei, 11% in Yap and 8% in Kosrae, with almost 23% living in urban areas.

Mongolia is the fifth largest country in Asia, covering a total area of 1.6 million square kilometres. In 2010, the population reached 2.78 million, giving an overall population density of 1.7 persons per square kilometre, and making it the least densely populated country in the world. Of the total population, 27.3% are under the age of 15 years, 68.8% between 15-64 years of age and only 3.9% are aged 65 years and above. Males comprise 48.6% of the population, and 63.3% of the total population live in urban areas. The adult literacy rate is reported to be 97.8%.

Nauru, an island in the Central Pacific Ocean, joined WHO on 9 May 1994. In 1968, the Republic gained its independence from Australia, New Zealand and British-administered UN trusteeship. It is covered by the WHO Representative Office in the South Pacific.

New Caledonia became a French territory in 1853. In 1946 it became an overseas territory of the French Republic. Direct rule by France was discontinued on 14 July 1989, and the provincial councils gained a degree of limited autonomy. It was covered by the WHO Representative Office in the South Pacific.

New Zealand, one of the WHO founders, participated in the International Health Conference in 1946, which resutled in the drafting of the WHO constitution, turning over the functions of the Office International d'Hygiene Publique (OIHP) to WHO and setting up of an Interim Commision to prepare for the First WOrld Health Assembly. It joined WHO on 10 December 1946. It is covered by the WHO Representative Office in the South Pacific.

At the Sixth World Health Assembly in May 1953, Niue was assigned to the Western Pacific Region as an area, ''without prejudice to any questions regarding sovereignty.'' It achieved internal self-government in October 1974 in free association with New Zealand. Niue joined WHO on 4 May 1994.

In May 1953, Palau was assigned to the Western Pacific Region at the Sixth World Health Assembly ''without prejudice to any questions regarding sovereignty'' as an area. It was a member of the UN Trust Territory of the Pacific Islands dominated by the United States of America until the Office of the High Commissioner determined to end the association on 10 July 1987. All functions were transferred to individual governments, including Palau. On 9 March 1995, Palau joined WHO as one of its Member States.

Papua New Guinea is one of the most diverse countries in the world - geographically, biologically, linguistically, and culturally. Its abundant natural resources have not led yet to economic prosperity for the majority of its people. PNGs relative level of poverty in relation to neighbouring countries is increasing and it now ranks 145th out of 177 countries on the United Nations Development Programme Human Development Index. Papua New Guinea has an estimated population of around 6.7 million (2010), 38.2% under the age of 15. Around 800 languages are spoken in the country, each language group having a distinct culture, and there are large sociocultural differences between and within provinces. The official languages are English, Pidgin and Motu. Access to widely scattered rural communities (87.5% of the country’s population is living in rural areas) is often difficult, slow and expensive. Only 3% of the roads are paved and many villages can only be reached on foot. Most travel between provinces is by air. The capital, Port Moresby, is not linked by road to the rest of the country.

The population of the Philippines, as of the last census in 2007, numbered 88 574 614, with a population density of 295 per square kilometre. This translates to an average annual population growth rate of 2.0% for the period from 2000 to 2007, which was the lowest annual population growth rate recorded for the Philippines since the 1960s.

The Pitcairn Islands is an overseas territory of the United Kingdom of Great Britain and Northern Ireland, consisting of four islands in the South Pacific Ocean. Only one island with an area of 46 square kilometres is inhabited. The Pitcairn Islands is governed by the mayor and chairman of the Island Council, elected by popular vote. The head of state is represented by a United Kingdom high commissioner and a governor.

The Republic of Korea joined WHO on 17 August 1949. It was covered by the WHO Representative Office in Taipei, China (Taiwan) from 1959 to 1 January 1965, when the WHO Representative Office in Seoul, Republic of Korea was established.

Samoa is a Pacific island state comprising two main islands, Savaii and Upolu, plus several smaller islands. It lies about half way between Hawaii and New Zealand and has a land area of around 2842 square kilometers. Its main economic activities are tourism, fishing and agriculture. The country is divided into four major statistical regions: Apia Urban Area (AUA), North West Upolu, Rest of Upolu (including Manono and Apolima Islands) and Savaii. AUA represents the urban area, while the other three regions are rural. In 2010, estimates put Samoa’s population at 184 032, with around 38.3% young people aged less than 15 years and only 5.0% aged 65 years and over. Life expectancy was 73.2 according to the 2006 census, compared with 72.8 years in 2001.

In May 1953, Singapore was assigned to the Western Pacific Region at the Sixth World Health Assembly ''without prejudice to any questions regarding sovereignty'' as an Area.

Solomon Islands is a double-chain archipelago of more than 900 coral atolls located in the south-west Pacific Ocean about 1800 kilometres north-east of Australia. Its total land area of 30 400 square kilometres is widely scattered over 1.3 million square kilometres (exclusive economic zone) of the Pacific, with most of its smaller islands uninhabited. The population at the latest National Census in 2009 was 515 870. An estimated 93% of the total population are Melanesians, 4% are Polynesians and 3% are from other ethnic groups. According to the 2009 Census, the population is growing at a rate of 2.3% per annum. Most live in rural areas, with only 18% living in urban areas.

In May 1953, Tonga was assigned to the Western Pacific Region at the Sixth World Health Assembly ''without prejudice to any questions regarding sovereignty'' as an area. Tonga was under the British protectorate from 1900 to 4 June 1970, the same date its independence was restored. It joined WHO on 15 August 1975 as a Member State. It was covered by the WHO Representative Office in the South Pacific since its establishment, and the WHO Country Liaison Officer was designated in March 1981.

Tuvalu comprises nine coral islands and is, by population, the smallest member of the United Nations.

The 2009 National Census of Population and Housing reported the population of Vanuatu to be 234 023, with a growth rate of 2.3% per annum. Life expectancy at birth is 69 for males and 72 for females, and 3.5% of the population is over 65 years of age. The 2011 estimated crude birth rate was 31.1 per 1000 population and the estimated crude death rate was 5.3. The infant mortality rate was 27 per 1000 live births in 2008. According to the last national census, the urban population accounted for 25.6% of the total population in 2010. Urban migration is increasing at an alarming rate, particularly from rural islands to Port Vila and Luganville, as people seek employment or education. Most of the population are employed in subsistence agriculture, the rest being in government departments, private companies and other employment sectors.

Viet Nam has 54 different ethnic groups, with the Kinh representing 87% of the total population. The rest are ethnic minorities scattered all over the country, mostly in mountainous and remote areas. Population migration is an important factor in rural-urban population growth differentials. The General Statistics Office survey on migration and family planning indicates that substantial spontaneous migration has been taking place and that migrants from rural to urban areas are numerous. The estimated population of Viet Nam was 86 025 000 in 2009, 49.4% of them male. The population density is 263 persons per square kilometre, with most (70.3%) of the population living in rural areas.