 The Yap Islands in the Pacific Ocean, with a land area of 100.2 square kilometres (38.7 sq mi) and a population of 6,300 (in 2003) |
The 2007 Yap Islands Zika virus outbreak represented the first time Zika virus had been detected outside Africa and Asia. It occurred in the Yap Islands, an island chain in the Federated States of Micronesia. Zika virus (ZIKV) is a vector-borne flavivirus in the same family as yellow fever, dengue, West Nile and Japanese encephalitis viruses. [1] [2]
In 2007, physicians in the Yap Islands reported to the Centers for Disease Control and Prevention an outbreak of an illness characterized by rash, conjunctivitis, and arthralgia. Initial serum testing revealed some patients had the IgM antibody against dengue virus, yet the patients' signs and symptoms were clinically distinct from dengue fever. Subsequent retesting using consensus primers detected the presence of Zika virus RNA. [3]
A household survey was conducted to determine the proportion of Yap residents with the IgM antibody against Zika virus and to identify possible mosquito vectors of Zika virus. In total, the Yap Islands outbreak had 49 confirmed and 59 probable cases of Zika virus disease. The patients resided in 9 of the 10 municipalities on Yap. None of the patients required hospitalization. No hemorrhagic manifestations occurred and no deaths resulted. It was 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. [3]
The outbreak of Zika fever in Micronesia demonstrated the transmission of Zika virus outside Africa and Asia. This was considered a significant finding in that previously only 14 cases of Zika virus had been documented since the virus was first identified in 1947. Prior to the Yap Islands outbreak, no previous outbreaks of Zika virus had ever been reported and only 14 cases had been documented since the virus was first isolated in 1947. All previous cases had occurred within Africa and Asia. [3] [2]
Aedes aegypti has been recognized as the vector of Zika virus. The virus was first isolated in 1947 from a sentinel rhesus monkey stationed on a tree platform in the Zika forest, Uganda. [4] [2]
Transmission is typically via the bite of the Aedes aegypti mosquito, although in this outbreak, Aedes hensilli was the predominant mosquito species identified. [3] [5]
Yellow fever is a viral disease of typically short duration. In most cases, symptoms include fever, chills, loss of appetite, nausea, muscle pains – particularly in the back – and headaches. Symptoms typically improve within five days. In about 15% of people, within a day of improving the fever comes back, abdominal pain occurs, and liver damage begins causing yellow skin. If this occurs, the risk of bleeding and kidney problems is increased.
Dengue fever is a mosquito-borne tropical disease caused by the dengue virus. Symptoms typically begin three to fourteen days after infection. These may include a high fever, headache, vomiting, muscle and joint pains, and a characteristic skin itching and skin rash. Recovery generally takes two to seven days. In a small proportion of cases, the disease develops into a more severe dengue hemorrhagic fever, resulting in bleeding, low levels of blood platelets and blood plasma leakage, or into dengue shock syndrome, where dangerously low blood pressure occurs.
Aedes or Pointy Mosquito is a genus of mosquitoes originally found in tropical and subtropical zones, but now found on all continents except Antarctica. Some species have been spread by human activity: Aedes albopictus, a particularly invasive species, was spread to the Americas, including the United States, in the 1980s, by the used-tire trade.
Flavivirus is a genus of positive-strand RNA viruses in the family Flaviviridae. The genus includes the West Nile virus, dengue virus, tick-borne encephalitis virus, yellow fever virus, Zika virus and several other viruses which may cause encephalitis, as well as insect-specific flaviviruses (ISFs) such as cell fusing agent virus (CFAV), Palm Creek virus (PCV), and Parramatta River virus (PaRV). While dual-host flaviviruses can infect vertebrates as well as arthropods, insect-specific flaviviruses are restricted to their competent arthropods. The means by which flaviviruses establish persistent infection in their competent vectors and cause disease in humans depends upon several virus-host interactions, including the intricate interplay between flavivirus-encoded immune antagonists and the host antiviral innate immune effector molecules.
Dengue virus (DENV) is the cause of dengue fever. It is a mosquito-borne, single positive-stranded RNA virus of the family Flaviviridae; genus Flavivirus. Four serotypes of the virus have been found, and a reported fifth has yet to be confirmed, all of which can cause the full spectrum of disease. Nevertheless, scientists' understanding of dengue virus may be simplistic as, rather than distinct antigenic groups, a continuum appears to exist. This same study identified 47 strains of dengue virus. Additionally, coinfection with and lack of rapid tests for Zika virus and chikungunya complicate matters in real-world infections.
Aedes aegypti, the yellow fever mosquito, is a mosquito that can spread dengue fever, chikungunya, Zika fever, Mayaro and yellow fever viruses, and other disease agents. The mosquito can be recognized by black and white markings on its legs and a marking in the form of a lyre on the upper surface of its thorax. This mosquito originated in Africa, but is now found in tropical, subtropical and temperate regions throughout the world.
The 2006 dengue outbreak in Pakistan was at the time the worst on record. There were 1931 lab-confirmed cases, and 41 confirmed deaths, according to the World Health Organization Regional Office for the Eastern Mediterranean. Other sources report a death toll of 52.
Zika fever, also known as Zika virus disease or simply Zika, is an infectious disease caused by the Zika virus. Most cases have no symptoms, but when present they are usually mild and can resemble dengue fever. Symptoms may include fever, red eyes, joint pain, headache, and a maculopapular rash. Symptoms generally last less than seven days. It has not caused any reported deaths during the initial infection. Mother-to-child transmission during pregnancy can cause microcephaly and other brain malformations in some babies. Infections in adults have been linked to Guillain–Barré syndrome (GBS).
A reverse zoonosis, also known as a zooanthroponosis or anthroponosis, is a pathogen reservoired in humans that is capable of being transmitted to non-human animals.
Mosquito-borne diseases or mosquito-borne illnesses are diseases caused by bacteria, viruses or parasites transmitted by mosquitoes. Nearly 700 million people get a mosquito-borne illness each year resulting in over 725,000 deaths.
Zika virus is a member of the virus family Flaviviridae. It is spread by daytime-active Aedes mosquitoes, such as A. aegypti and A. albopictus. Its name comes from the Ziika Forest of Uganda, where the virus was first isolated in 1947. Zika virus shares a genus with the dengue, yellow fever, Japanese encephalitis, and West Nile viruses. Since the 1950s, it has been known to occur within a narrow equatorial belt from Africa to Asia. From 2007 to 2016, the virus spread eastward, across the Pacific Ocean to the Americas, leading to the 2015–2016 Zika virus epidemic.
Aedes polynesiensis is only found in the South Pacific on the islands of Austral Islands, Cook Islands, Ellice Islands, Fiji Islands, Hoorn Islands, Marquesas Islands, Pitcairn Island, Samoa Islands, Society Islands, Tokelau Islands, Tuamotu Archipelago. It is a vector of dengue, Ross River virus, and lymphatic filariasis, and a probable vector of Zika virus. Adults lay eggs in natural and human-associated pools of freshwater. Common larval habitats include tree holes, holes in volcanic rock formations, coconut shells, water storage containers (drums), and discarded trash.
A lethal ovitrap is a device which attracts gravid female container-breeding mosquitoes and kills them. The traps halt the insect's life cycle by killing adult insects and stopping reproduction. The original use of ovitraps was to monitor the spread and density of Aedes and other container-breeding mosquito populations by collecting eggs which could be counted, or hatched to identify the types of insects. Since its conception, researchers found that adding lethal substances to the ovitraps could control the populations of these targeted species. These traps are called lethal ovitraps. They primarily target Aedes aegypti and Aedes albopictus mosquitoes, which are the main vectors of dengue fever, Zika virus, west Nile virus, yellow fever, and chikungunya.
Aedes africanus is a species of mosquito that is found on the continent of Africa with the exclusion of Madagascar. Aedes aegypti and Aedes africanus are the two main yellow fever vector species in Zambia. Aedes africanus is mainly found in tropical forests not near wetlands.
An epidemic of Zika fever, caused by Zika virus, began in Brazil and affected other countries in the Americas from April 2015 to November 2016. The World Health Organization (WHO) declared the end of the epidemic in November 2016, but noted that the virus still represents "a highly significant and long term problem". It is estimated that 1.5 million people were infected by Zika virus in Brazil, with over 3,500 cases of infant microcephaly reported between October 2015 and January 2016. The epidemic also affected other parts of South and North America, as well as several islands in the Pacific.
The ZikaForest is a tropical forest near Entebbe in Uganda. Ziika means 'overgrown' in the Luganda language. As the property of the Uganda Virus Research Institute (UVRI) of Entebbe, it is protected and restricted to scientific research.
Spondweni virus is an arbovirus, or arthropod-borne virus, which is a member of the family Flaviviridae and the genus Flavivirus. It is part of the Spondweni serogroup which consists of the Sponweni virus and the Zika virus (ZIKV). The Spondweni virus was first isolated in Nigeria in 1952, and ever since, SPONV transmission and activity have been reported throughout Africa. Its primary vector of transmission is the sylvatic mosquito Aedes circumluteolus, though it has been isolated from several different types of mosquito. Transmission of the virus into humans can lead to a viral infection known as Spondweni fever, with symptoms ranging from headache and nausea to myalgia and arthralgia. However, as SPONV is phylogenetically close to the ZIKV, it is commonly misdiagnosed as ZIKV along with other viral illnesses.
Aedes hensilli is a mosquito species originally collected in 1945 on Ulithi atoll in the Caroline Islands of the western Pacific Ocean, about 191 km east of Yap State. It is the most abundant and widespread Aedes (Stegomyia) species mosquito in Yap State, the only Aedes (Stegomyia) species on Woleai, and the only species of mosquito present on Eauripik.
In October 2013, there was an outbreak of Zika fever in French Polynesia, the first outbreak of several Zika outbreaks across Oceania. With 8,723 cases reported, it was the largest outbreak of Zika fever before the outbreak in the Americas that began in April 2015. An earlier outbreak occurred on Yap Island in the Federated States of Micronesia in 2007, but it is thought that the 2013–2014 outbreak involved an independent introduction of the Zika virus from Southeast Asia. Investigators suggested that the outbreaks of mosquito-borne diseases in the Pacific from 2012 to 2014 were "the early stages of a wave that will continue for several years", particularly because of their vulnerability to infectious diseases stemming from isolation and immunologically naive populations.
This article primarily covers the chronology of the 2015–16 Zika virus epidemic. Flag icons denote the first announcements of confirmed cases by the respective nation-states, their first deaths, and relevant sessions and announcements of the World Health Organization (WHO), and the U.S. Centers for Disease Control (CDC), as well as relevant virological, epidemiological, and entomological studies.
