Zika virus outbreak (2015–present)
Countries and territories with active transmission of the Zika virus
as of 4 April 2016 [1] |
| Date |
April 2015 – present |
As of early 2016, a widespread outbreak of Zika fever, caused by the Zika virus, is ongoing in the Americas and the Pacific.[2] The outbreak began in April 2015 in Brazil, and has spread to other parts of South and North America; it is also affecting several islands in the Pacific. In January 2016, the World Health Organization (WHO) said the virus was likely to spread throughout most of the Americas by the end of the year.[3]
In February 2016, WHO declared the outbreak a Public Health Emergency of International Concern as evidence grew that Zika is a cause of birth defects and neurological problems.[4][5] Zika is transmitted from pregnant women to the fetus (“vertical transmission“), and causes microcephaly and other severe brain anomalies in infants born of women infected with the virus.[6][7][8] Zika infections in adults can result in Guillain-Barré syndrome.[8] Prior to this outbreak, Zika was considered a mild infection, as most Zika virus infections are asymptomatic, making it difficult to determine precise estimates of the number of cases.[9] In approximately one in five cases, Zika virus infections result in Zika fever, a minor illness that causes symptoms such as fever and a rash.
The virus is spread mainly by the Aedes aegypti mosquito, which is commonly found throughout the tropical and subtropical Americas. It can also be spread by the Aedes albopictus (“Asian tiger”) mosquito, which is distributed as far north as theGreat Lakes region in North America.[10] Sexual transmission of the Zika virus is also possible.[5][11][12][13]
A number of countries have issued travel warnings, and the outbreak is expected to affect the tourism industrysignificantly.[5][14] Several countries have taken the unusual step of advising their citizens to delay pregnancy until more is known about the virus and its impact on fetal development.
Epidemiology[edit]
Cases in the Americas[16]
[hide]Country
as of 14 April 2016 |
Autochthonous cases |
Deaths |
| Confirmed |
Suspected |
 Aruba |
4 |
|
|
 Barbados |
7 |
316 |
|
 Bolivia[17] |
25 |
|
|
 Bonaire |
1 |
|
|
 Brazil[a] |
526 |
72,062 |
4 |
 Colombia |
3,061 |
61,778 |
|
 Costa Rica[18] |
12 |
|
|
 Cuba |
1 |
|
|
 Curaçao |
1 |
|
|
 Dominica |
1 |
|
|
 Dominican Republic |
56 |
1,249 |
1 |
 Ecuador |
71 |
139 |
|
 El Salvador |
43 |
11,011 |
|
 French Guiana |
355 |
3,620 |
|
 Guadeloupe |
191 |
1,090 |
|
 Guatemala |
261 |
915 |
|
 Guyana |
1 |
|
|
 Haiti |
5 |
1,777 |
|
 Honduras |
2 |
17,556 |
|
 Jamaica[19] |
4 |
|
|
 Martinique |
12 |
16,650 |
|
 Mexico |
222 |
|
|
 Nicaragua |
135 |
|
|
 Panama |
220 |
|
|
 Paraguay |
7 |
|
|
 Puerto Rico |
436 |
|
|
 Saint Lucia |
2 |
|
|
 Saint Martin |
42 |
160 |
|
 Saint Vincent and the Grenadines |
1 |
|
|
 Sint Maarten |
2 |
|
|
 Suriname |
485 |
3,440 |
4 |
 Trinidad and Tobago |
13 |
|
|
 U.S. Virgin Islands |
14 |
54 |
|
 Venezuela |
352 |
15,495 |
1 |
| Total |
6,560 |
207,312 |
10 |
- Jump up^ Early in 2016, Brazil abandoned the effort to update the number of Zika cases; 526 confirmed cases were reported 11 February; the number of suspected cases was an unofficial estimate (through media monitoring) at that time.[20]
In 2015, Brazil estimated a minimum of 497,593 and a maximum of 1,482,701 cases.[21]
- Jump up^ Because numbers in the columns may be from more than one source, the sum of the numbers in each column may not equal the totals listed here, which are from a single source.
|
As early as August 2014, physicians in Natal in northeastern Brazil began to investigate an outbreak of illness characterized by a flat pinkish rash, bloodshot eyes, fever, joint pain and headaches. While the symptoms resembled dengue fever, testing ruled out this and several other potential causes. By March 2015, the illness had spread to Salvador, Bahia and had appeared in three different states.[62] Then, in May 2015, researchers from the Federal University of Bahia and the Evandro Chagas Institute determined, using the RT-PCR technique, that the illness was an outbreak of Zika virus.[63][64]
The Zika virus was first isolated in 1947, in a rhesus monkey in a forest nearEntebbe, Uganda.[65] Although serologic evidence indicated additional human exposure during subsequent decades in parts of Africa and Asia,[66] before the2007 Yap Islands Zika virus outbreak, only 14 cases of human Zika virus disease had been documented.[65]
Researchers generally believe the virus was brought to Brazil by an infected traveler who had been exposed to the virus in French Polynesia, who was then bitten by a mosquito that then infected others.[67][68][69] Phylogeneticanalysis of the first Brazilian infections have strongly indicated that the circulating virus is the Asian, rather than African, strain of the virus, and was genetically similar to the virus found in the outbreak in French Polynesia.[68][69]It appears Zika’s route – from Africa and Asia to Oceania and then the Americas – may mirror that of chikungunya and dengue, both of which are endemic in a large portion of the Americas.[70]
The specific event that brought the virus to Brazil was uncertain until March 2016. Brazilian researchers have suggested that the Zika virus arrived during the 2014 FIFA World Cup tournament.[67] French researchers speculated the virus arrived shortly afterwards, in August 2014, when canoeing teams from French Polynesia, New Caledonia, Easter Island, and the Cook Islands, whichhad been or were experiencing Zika outbreaks, attended the Va’a World Sprint Championships in Rio de Janeiro.[62][68] However, the outbreak in French Polynesia is known to have peaked and declined precipitously by February 2014, lending doubt to the suggestion the virus arrived later that year in Brazil with spectators and competitors.[71] A study published in Science, which developed a “molecular clock” based on the count of virus mutations in a relatively small sample, suggested Zika virus arrived in the Americas (most likely in Brazil) from French Polynesia between May and December 2013, well before the World Cup and Va’a Championships.[71] In the Science article, Faria and colleagues managed to trace the origins of the virus strain that is circulating in Brazil and found out that this strain has few genetic variability when compared to the strain of French Polynesia; after relating the number of travellers arriving in Brazil from French Polynesia with the cases reported and the events happening in that year, the team was able to prove that the virus arrived in Brazil on 2014 during the Confederation Cup, when Tahiti’s team played against other teams in a few brazilians cities, which attracted a lot of tourists from both places.[72] Zika virus usually has very mild, or no symptoms, so it took almost a year for Brazil to confirm the first case of the disease. By then the outbreak was already widespread.. Factors associated with the rapid spread of Zika virus in Brazil include the non-immune population, high population density, tropical climate and inadequate control of Aedesmosquitoes in the country.[73]
Confirmed cases have now been reported in most of South and Central America, and the Caribbean.[74] Cases have also been reported that were imported from South America into Europe,[75] Canada,[76] United States,[77]China,[78] and Australia.[79]
Transmission[edit]
Zika is a mosquito-borne disease. Zika can also be sexually transmitted from a man to his sex partners.[80] The resurgence of Aedes aegypti‘s worldwide distribution over the past 2–3 decades makes it one of the most widely distributed mosquito species.[81] In 2015, Aedes albopictus was present intropical, subtropical, and temperate regions of the Americas, reaching as far north as the Great Lakes of North America and, internationally, living alongside Aedes aegypti in some tropical and subtropical regions.[10]
The Aedes aegypti mosquito usually bites in the morning and afternoon hours, and can be identified by the white stripes on its legs.[82] The mosquito species (Aedes aegypti, mainly, and Aedes albopictus) that can spread Zika virus can also spread dengue, chikungunya, and yellow fever.[83]
Sexual transmission of Zika has been documented in six countries—Argentina, Chile, France, Italy, New Zealand and the United States of America—during this outbreak.[8][80]
Zika is transmitted from pregnant women to the fetus (“vertical transmission“), and causes microcephaly and other severe brain anomalies in infants born of women infected with the virus.[6][8]
A baby with microcephaly (left) compared to a baby with a typical head size
Zika infections in adults can cause Guillain-Barré syndrome.[8]
Containment and control[edit]
Diagnosis[edit]
Symptoms of Zika virus[84]
Symptoms are similar to other flaviviruses such as dengue fever or the alphavirusthat causes chikungunya,[85] but are milder in form and usually last two to seven days.[5] It is estimated that 80% of cases are asymptomatic.[11] The main clinical symptoms in symptomatic patients are low-grade fever, conjunctivitis, transient joint pain (mainly in the smaller joints of the hands and feet) and maculopapular rashthat often starts on the face and then spreads throughout the body.[85]
It is difficult to diagnose Zika virus infection based on clinical signs and symptoms alone due to overlaps with other arboviruses that are endemic to similar areas.[86]The methods currently available to test for Zika antibodies cross-react with dengue antibodies. An IgM-positive result in a dengue or Zika ELISA test can only be considered indicative of a recent flavivirus infection. Plaque-reduction neutralization tests can be performed and may be specific.[87] The Zika virus can be identified byRT-PCR in acutely ill patients.[5]
Americas[edit]
Several countries, including Colombia, Ecuador, El Salvador, and Jamaica, advised women to postpone getting pregnant until more was known about the risks.[15][88]Plans were announced by the authorities in Rio de Janeiro, Brazil, to try to prevent the spread of the Zika virus during the 2016 Summer Olympics in Rio.[89] Thehealth ministry of Peru installed more than 20,000 ovitraps during the 2015 dengue outbreak. The same ovitraps will be used to monitor a potential Zika outbreak in tropical regions of Peru.[90]
Symptoms of microcephaly, linked to mothers infected by Zika virus.[84]
Because of the “growing evidence of a link between Zika and microcephaly” the CDC issued a travel warning on 15 January 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.[91] On 20 January, the Ministry of Health of Chile published a health notice.[92] On 22 January, eight more countries and territories were added to the list of those affected: Barbados, Bolivia, Ecuador,Guadeloupe, Saint Martin, Guyana, Cape Verde, and Samoa.[93] On 1 February,Costa Rica and Nicaragua were added to the list, bringing the number of countries and territories affected to 28.[94]
The agency issued additional guidelines and suggested that women thinking about becoming pregnant consult with their physicians before traveling.[95] Canada issued a similar travel advisory.[89][96]
On 5 February 2016, after the laboratory confirmation of a Zika virus infection in the U.S. in a non-traveler, which was linked to sexual contact with an infected partner, the CDC issued interim guidelines for prevention of sexual transmission of Zika virus for the United States.[11] These guidelines recommend that men who reside in or have traveled to an area of active Zika virus transmission who have a pregnant partner should abstain from sexual activity or consistently and correctly use condoms during sex for the duration of the pregnancy.[11] The guidelines recommend that pregnant women discuss any possible Zika exposure with their male partners.[11] The guidelines recommend that non-pregnant women and their partners consider taking similar measures.[11] On 8 February 2016, CDC elevated its response efforts to a Level 1 activation, the highest response level at the agency. On 23 February 2016, the CDC issued a statement further encouraging adherence to this guidance after 14 reports of possible sexual transmission of the virus were under investigation.[12][13]
On 18 March 2016, Centers for Disease Prevention and Control cautioned men who have been infected with Zika from attempting to conceive children due to probability of virus transfer from man to woman during sexual activity which in turn can affect the fetus, under this caution, men are advised not to try conception until six months after the infection.[97]
International[edit]
Governments or health agencies such as those of the United Kingdom,[98]Ireland,[88] Japan,[99] South Korea,[100] New Zealand,[101] Malaysia,[102]Philippines[103] and the European Union[89] issued travel warnings. The warnings are predicted to have an effect on the tourism industry in affected countries.[104][105][106]
To prevent the transmission of the Zika virus, WHO recommends using insect repellent, wearing long-sleeved clothes to cover the body, and using screens andmosquito nets to exclude flying insects from dwellings or sleeping areas. It is also vital to eliminate any standing water near homes to minimize breeding areas for mosquitoes. Authorities can treat larger water containers with recommendedlarvicides.[82][107] Furthermore, the Centers for Disease Control and Prevention(CDC) recommends that containers holding water near homes either be sealed or scrubbed once per week, because mosquito eggs can stick to them.[83]
On 1 February 2016, WHO declared the cluster of microcephaly cases and other neurological disorders a Public Health Emergency of International Concern,[4] which may reduce the number of visitors to the Rio Olympics in 2016.[108] The designation has been applied in the past to the Ebola outbreak in 2014, the outbreak of polio in Syria in 2013, and the 2009 flu pandemic.[109] South Korea held an emergency meeting in response to the WHO declaration in 2 February 2016.[100] A second meeting of the WHO-convened emergency committee, held on 8 March 2016, reaffirmed the situation’s status as a Public Health Emergency of International Concern. The committee reported that evidence was increasing for a causal relationship between Zika virus and microcephaly and other neurological conditions, and called for continued research, aggressive mosquito control, and improved surveillance and communication of risks to the public. The report stated that pregnant women should be advised not to travel to affected areas, and should use safe sex practices if their partners lived in or travelled to affected areas throughout their pregnancy.[110] On 9 March 2016, WHO announced that research should prioritise prevention and diagnosis, not treatment, and in particular non-live vaccines suitable for pregnant women and those of childbearing age, novel mosquito control measures, and diagnostic tests that can detect dengue and chikungunya as well as Zika.[111]
Responses[edit]
The Brazilian Army has sent more than 200,000 troops to go “house to house” in the campaign against Zika-carrying mosquitoes.
Brazilian Army soldier analyzes the water from a cistern
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 mosquitoes throughout their country.[112] Previously, in July 2015, Oxitec had published 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.[112][113][114] 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.[112][114]
On 1 February 2016, the WHO declared the current Zika virus outbreak an international public health emergency,[4][115] and the Brazilian President released a decree that increased local and federal pest control agents’ access to private property required by mobilization actions for the prevention and elimination ofAedes mosquito outbreaks in the country.[116]
Some experts have proposed combatting the spread of the Zika virus by breeding and releasing mosquitoes that have either been genetically modified to prevent them from transmitting pathogens or that have been infected with the Wolbachiabacterium, thought to inhibit the spread of viruses.[117][118] Another proposed technique consists of using radiation to sterilize male larvae so that when they mate, they produce no progeny.[119] Male mosquitoes do not bite or spread disease.[120]
In February, the Brazilian federal government mobilized 60% of the country’s Armed Forces, or about 220,000 soldiers, to warn and educate the populations of 350municipalities on how to reduce mosquitoes breeding grounds.[121]
A joint statement on the sharing of data and results on the Zika outbreak in the Americas and future public health emergencies was issued on 10 February 2016 by a group of more than 30 global health bodies.[122] The statement reinforces a similar consensus statement issued by WHO in September 2015.[123] The statement calls for free access to all data as rapidly and widely as possible.[124]
In February 2016, Google announced that they were donating $1 million via UNICEF to fight the spread of the Zika virus and offering professional personnel to help to determine where it will hit next.[125]
Controversies[edit]
Some efforts to contain the spread of Zika virus have been controversial. Oxitec, the company behind the “self-limiting” mosquitoes released in Brazil, has faced criticism from environmental groups, who fear that releasing a new mosquito strain into the wild will damage the ecosystem. In the short term, the concern is that a drop in the mosquito population could affect the populations of other species. Supporters claim that the environmental impact of the “self-limiting” mosquitoes will be minimal, since only one species of mosquito is being targeted and the genetically-modified mosquitoes are still safe for predators to eat. Oxitec Product Development Manager Derric Nimmo likened the process to “going in with a scalpel and taking away Aedes aegypti, leaving everything untouched.”[126] Since Aedes aegypti is an imported invasive species in Brazil, some experts expect that its eradication will have little impact on the environment. However, other environmentalists emphasize that the long-term consequences of eliminating an entire species cannot be predicted.[127]
Government recommendations that women delay pregnancy have also proven to be controversial. Human andreproductive rights groups have deemed the recommendations irresponsible and difficult to follow, since women alone are tasked with avoiding pregnancy despite having little control to do so.[128] Evidence suggests that over half of the pregnancies in Latin America and the Caribbean are unplanned.[129] Access to contraceptives is limited in the predominantly Roman-Catholic region,[130] and widespread sexual violence results in many women getting pregnant against their will. Anti-abortion laws in much of the region leave women with no recourse once they become pregnant. Aside from three countries where abortion is widely available (French Guiana, Guyana, and Uruguay) and three countries where abortion is allowed in cases of fetal malformation (Colombia, Mexico, and Panama), most of the region only permits abortion in the cases of rape, incest, or danger to the mother’s health. In El Salvador, abortion is illegal under all circumstances.[128]
On 5 February 2016, the UN High Commissioner for Human Rights urged Latin American governments to consider repealing their policies regarding contraception and abortion, emphasizing that “upholding human rights is essential to an effective public health response.”[131] On 16 February 2016, the Vatican condemned the UN for its call to action, deeming it “an illegitimate response” to the Zika crisis and emphasizing that “a diagnosis of microcephaly in a child should not warrant a death sentence.”[132]
On 18 February 2016, after a trip to Latin America, Pope Francis stated that “avoiding pregnancy is not an absolute evil” in cases such as the Zika virus outbreak. His comments sparked speculation that the use of contraception may be morally permissible in the fight against the Zika virus.
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