Zika virus outbreak in the Americas (2015–present)
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Situation map of the outbreak as of January 2016
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April 2015–present
b There are 3174 cases and 38 deaths from microcephaly.[22] |
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Main articles: Zika virus and Zika fever
As of early 2016, the most widespread outbreak of Zika virus in history is ongoing in the Americas.
The outbreak began in April 2015 in Brazil, and subsequently spread to
other countries in South America, Central America, and the Caribbean.In January 2016, the World Health Organization (WHO) said that the virus was likely to spread throughout the majority of the Americas by the end of the year.[23] The virus is mainly spread by the Aedes aegypti mosquito, which is commonly found throughout the the tropical and subtropical Americas, but also Aedes albopictus that now have become widespread up to the Great Lakes area of the USA. Both have white stribes and marks and can spread more diseases. [24]
In around one in five cases, infection with Zika virus results in a minor illness known as Zika fever, which causes symptoms such as fever and a rash. However, Zika virus infection in pregnant women has been linked with thousands of cases of newborn microcephaly by mother-to-child transmission. A number of countries have issued travel warnings, and the virus was detected in cases in the U.S.,[25] Denmark,[26] as well as six in Portugal.[27]
Contents
Epidemiology
See also: Zika virus § Transmission
In May 2015, Zika virus was first confirmed as the cause of an outbreak of a dengue-like disease in northern and eastern Brazil.[28] In the district of Camaçari and the neighboring city Salvador, capital of the state of Bahia, a previously unknown disease affecting patients with flu-like symptoms followed by rash and arthralgia, was shown to be caused by Zika virus by researchers from the Federal University of Bahia using the RT-PCR technique.[29] The spread followed a pattern similar to an outbreak of Chikungunya virus in the same region, another disease previously unknown to the local population. The virus reached Colombia in October[30] and other countries in Latin America including the Caribbean in November and December.[31] Confirmed cases have now been reported in most of South and Central America, and the Caribbean.[32]Cases have also been reported that were imported from South America into Europe and the United States. One case was a traveler who returned in March 2015 to Italy from Brazil.[33] A few cases of imported Zika virus infection have been reported in the United States[34] and Australia.[35]
In January, three cases have been reported in the United Kingdom[36] and three in Canada.[37] Two cases included tourists returning to Switzerland from Haiti and Colombia, and one case of a Danish man who returned, after visiting Central and South America.[38]
Link to infant microcephaly and other neurological and ocular disorders
A baby with microcephaly (left) compared to a baby with a typical head size
Zika virus was first linked with newborn microcephaly during the Brazil Zika virus outbreak. In 2015, there were 2,782 cases of microcephaly compared with 147 in 2014 and 167 in 2013.[40]
In November 2015, Zika virus was isolated in a newborn from the northeastern state of Ceará, Brazil, with microcephaly and other congenital issues. The Lancet medical journal reported in January 2016 that the Brazilian Ministry of Health had confirmed 134 cases of microcephaly "believed to be associated with Zika virus infection" with an additional 2,165 cases in 549 counties in 20 states remaining under investigation.[41]
In January 2016, a baby in Oahu, Hawaii, was born with microcephaly, the first case in the United States of brain damage linked to the virus. The baby and mother tested positive for a past Zika virus infection. The mother, who had probably acquired the virus while traveling in Brazil in May 2015 during the early stages of her pregnancy, had reported her bout of Zika. She recovered before relocating to Hawaii. Although her pregnancy had progressed normally, the baby's condition was not known until birth.[42]
A high incidence of the autoimmune disease Guillain–Barré syndrome (GBS) noted in French Polynesia, has also been found in the outbreak that began in Brazil.[43] However, there are no laboratory confirmations of Zika virus infection in patients with GBS.[44]
Ocular disorders in newborns have also been linked to Zika virus infection.[45] In one study in Pernambuco state in Brazil, about 40 percent of babies with Zika-related microcephaly also had scarring of the retina with spots, or pigment alteration.[44]
Containment and control
Americas
Countries that have past or current evidence of Zika virus transmission (as of 15 January 2016)[46]
Because of the "growing evidence of a link between Zika and microcephaly" the U.S. Centers for Disease Control and Prevention (CDC) issued a travel alert on January 15, 2016 advising pregnant women to consider postponing travel to Brazil as well as the following countries and territories where Zika fever had been reported: Colombia, El Salvador, French Guiana, Guatemala, Haiti, Honduras, Martinique, Mexico, Panama, Paraguay, Suriname, Venezuela, and the Commonwealth of Puerto Rico.[51] On January 22, 2016, eight more countries were added to the list: Barbados, Bolivia, Ecuador, Guadeloupe, Saint Martin, Guyana, Cape Verde, and Samoa.[52] The agency issued additional guidelines and suggested that women thinking about becoming pregnant consult with their physicians before traveling.[53] Canada issued a similar travel advisory.[49]
The Ministry of Health of Chile published a health notice.[54]
International
Adult Aedes aegypti mosquito, a vector or carrier of the Zika virus
WHO recommendations for Zika virus prevention includes mainly using insect repellent; wearing clothes (preferably light-coloured) that cover as much of the body as possible; barriers like screens, closed doors and windows, and using mosquito nets. It is also important to prevent mosquitos breeding in water near homes, e.g. empty, clean or cover containers that can hold water such as buckets, flowerpots or tyres, so that places where mosquitoes can breed are removed. The Ades mosquito species usually bite in the morning and late afternoon. [57] Special help should be given to those who may not be able to protect themselves adequately. Health authorities may spray of insecticides in line with the WHO Pesticide Evaluation Scheme for larvicides to treat relatively large water containers. Furthermore, the Center for Disease Control recommends sealing or scrubbing containers with water near homes once per weak because mosquito eggs stick to them. The mosquito species (Aedes aegypti mainly and also Aedes albopictus), that can spread Zika virus, can also spread dengue, chikungunya, or yellow fever. They bite mainly at day-time and have e.g. white stripes at least on their legs. [58] In 2015, the mosquitto species was widely distributed in the Ammericas, up to the Great Lakes area of the USA, and internationally, with [Aedes aegypti] (mainly tropical and subtropical) and Aedes albopictus (mainly tropical,subtropical and temperate). [59]
Responses
Author and environmentalist Bill McKibben compared the virus outbreak to a dystopian climate future, when the range of viruses expands with climate warming.[60] A 2014 computer model of the Zika vector—the Aedes mosquito—predicts a more complicated change: "However, even if much of the tropics and subtropics will continue to be suitable, the climatically favourable areas for A. aegypti globally are projected to contract under the future scenarios produced by these models, while currently unfavourable areas, such as inland Australia, the Arabian Peninsula, southern Iran and some parts of North America may become climatically favourable for this mosquito species." [61] However, there are also signs that Zika virus capable mosquito populations adapting for persistence in a northern climate. Such a population has been identified in Washington D. C., and genetic evidence suggests they survived at least the last four winters in the region.[62]In January 2016 it was announced that in response to the Zika virus outbreak, Brazil’s National Biosafety Committee approved the releases of more genetically modified Aedes aegypti mosquitos throughout their country. Previously in July 2015, Oxitec released results of a test in the Juazeiro region of Brazil, of so-called “self-limiting” mosquitoes, to fight dengue, Chikungunya and Zika viruses. They concluded that mosquito populations were reduced by over 90% in the test region.[63][64][65] Male genetically modified mosquitoes mate with females in the wild and transmit a self-limiting gene that causes the resulting offspring to die before reaching adulthood and thus diminishes the local mosquito population.
See also
References
- Danilo O. Carvalho , Andrew R. McKemey , Luiza Garziera, Renaud Lacroix, Christl A. Donnelly, Luke Alphey, Aldo Malavasi, Margareth L. Capurro (2015). "Suppression of a Field Population of Aedes aegypti in Brazil by Sustained Release of Transgenic Male Mosquitoes". PLoS ONE 9 (7): e0003864. doi:10.1371/journal.pntd.0003864.
External links
- Flaviviridae Genomes database search results from the Viral Bioinformatics Resource Center
- Viralzone: Flaviviridae
- Virus Pathogen Database and Analysis Resource (ViPR): Flaviviridae
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Brazilian authorities estimate the country could have up to 1m Zika infections by now, and since September, the country has registered nearly 4,000 cases of babies with microcephaly.
The Rio de Janeiro authorities have announced plans to prevent the spread of the Zika virus during the Olympic Games later this year. ... The US, Canada and EU health agencies have issued warnings saying pregnant women should avoid travelling to Brazil and other countries in the Americas which have registered cases of Zika.
The New Zealand Government has followed Britain's lead. Official advice recommends any women who are pregnant or plan to conceive in the near future to delay travel to countries affected with the Zika virus.
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