In May 2015, an outbreak linked to the Zika virus was reported in Brazil, the first country in the Americas to be affected by the virus. The Zika virus then spread to various countries and territories in South and Central America, as well as to Africa, specifically Cape Verde. In December 2015, the first cases of Zika virus infection were confirmed in French Guiana and Martinique, followed in January 2016 by Guadeloupe and Saint Martin.

In 2013–2014, Oceania was once again affected, following the re-emergence of the Zika virus in 2007 in Micronesia (the island of Yap): a Zika virus outbreak affected more than 32,000 people in French Polynesia, and the outbreak then spread to New Caledonia, the Cook Islands, the Solomon Islands, and Easter Island.

The history of the various outbreaks is reported below.

Neurological complications likely linked to Zika virus infection, such as Guillain-Barré syndrome, were initially described in Brazil and French Polynesia. Furthermore, congenital malformations of the nervous system, such as microcephaly, have also been observed in fetuses and newborns of pregnant women, concurrently with Zika virus-related outbreaks; the observation of a temporal and spatial association between the presence of the Zika virus in these regions (Brazil/French Polynesia) and the increase in the number of microcephaly cases necessitates further investigation and research to better describe and understand these complications.

These findings have led to a public health alert in Brazil and French Polynesia.

Outbreak in Brazil, 2015

In May 2015, the Brazilian Ministry of Health informed the international community of local transmission of the Zika virus in the states of Bahia and Rio Grande do Norte (located in northeastern Brazil). Sixteen cases had been confirmed by the Evandro Chagas reference laboratory (8 cases in Bahia and 8 cases in Rio Grande do Norte).

These identifications followed numerous reports of rash-associated fever from seven states in northeastern Brazil—Bahia, Maranhão, Piauí, Pernambuco, Rio Grande do Norte, Sergipe, and Paraíba—since February 2015. As of April 29, 2015, a total of 6,807 suspected cases had been reported.

On December 1, 2015, the geographic spread of the Zika virus-related outbreak was confirmed in 18 states, and as of January 15, 2016, 20 states were affected: Federal District, Mato Grosso do Sul, Roraima, Amazonas, Pará, Rondônia, Mato Grosso, Tocantins, Maranhão, Piauí, Ceará, Rio Grande do Norte, Paraíba, Pernambuco, Alagoas, Bahia, Espírito Santo, Rio de Janeiro, São Paulo, and Paraná. (See map). These states are spread across the entire country, except for the west and northwest. As of December 2015, an estimated 500,000 to 1,500,000 suspected cases of Zika were reported across Brazil, and at least 34 cases have been confirmed by the Evandro Chagas reference laboratory.

While this virus appeared relatively harmless, neurological complications likely linked to Zika virus infection, such as Guillain-Barré syndrome, have been reported in Brazil. Furthermore, microcephaly and intrauterine brain development abnormalities have also been observed in fetuses and newborns of pregnant women, coinciding with Zika virus outbreaks; the observation of a temporal and spatial association between the presence of the Zika virus in these areas (Brazil) and the increase in the number of these complications necessitates further investigations and research to better describe and understand them.

[1] International Weekly Bulletin No. 531. Institute for Health Surveillance. 2015.

[2] Brazilian Ministry of Health: http://portalsaude.saude.gov.br/images/pdf/2016/janeiro/13/COES-Microcefalias---Informe-Epidemiol--gico-08---SE-01-2016---Valida----o-12jan2016---VALIDADO-PELO-CLAUDIO--e-com-os-estados-por-webconfer--n.pdf.

[3] Ministry of Health (Brazil). Public health event related to Zika fever cases [Internet]. 2015 [updated Aug 13, 2015, cited Aug 13, 2015]. Available from: http://portalsaude.saude.gov.br/index.php/oministerio/principal/secretarias/svs/noticias-svs/19139-evento-de-saude-publica-relacionado-aos-casos-de-febre-do-zika.

[4] Pan American Health Organization, World Health Organization. Regional Office for the Americas. Epidemiological Alert: Neurological syndrome, congenital malformations, and Zika virus infection. Implications for public health in the Americas [Internet]. Washington: World Health Organization, 2015 [updated Dec. 1, 2015, cited Dec. 1, 2015]. Available from: http://www.paho.org/hq/index.php?option=com_docman&task=doc_download&Itemid=&gid=32405&lang=en.

Outbreak in South and Central America, 2015

Since October 2015, the Zika virus has been circulating on the South American continent, and many countries (other than Brazil) or territories are reporting new locally acquired cases for the first time: Colombia, Suriname, Paraguay, El Salvador, Guatemala, Mexico, Panama, Honduras, Venezuela, Puerto Rico, French departments in the Americas (Martinique, Guadeloupe, Saint Martin, and French Guiana), Haiti, Guyana, Ecuador, Barbados, Bolivia, Ecuador, the Dominican Republic, the U.S. Virgin Islands, and Nicaragua.

An increase in the number of Guillain-Barré syndrome cases possibly linked to the Zika virus has also been reported in certain territories of the Americas [5].

In response to this situation, in early December 2015, the WHO recommended that South American countries establish a system for monitoring and managing Zika and implement surveillance for these complications.

[5] PAHO – Epidemiological alert – January 17, 2016: http://www.paho.org/hq/index.php?option=com_docman&task=doc_view&Itemid=270&gid=32879&lang=en.

Epidemic in Africa, 2015

The virus was first detected in sporadic cases or during seroprevalence surveys: its presence had been identified in Africa since the 1950s (Senegal, Uganda, Nigeria, Ivory Coast, Gabon, Tanzania, Egypt, Central African Republic, Sierra Leone, etc.). On November 2, 2015, the Cape Verdean Ministry of Health confirmed human cases of rash-associated fever linked to the Zika virus: laboratory tests conducted on blood samples sent to the Pasteur Institute in Dakar tested positive for the Zika virus. These were the first indigenous cases of Zika reported in Cape Verde. Cases had been reported in Praia (the capital), Santa Cruz (in the northeast of the island), and San Domingos (in the center of the island) on the island of Santiago 1 [6], 2 [7]. In early December 2015, Cape Verde’s Ministry of Health reported more than 4,100 cases [8] and implemented measures to monitor pregnant women more closely.

[6] International Weekly Bulletin No. 528. Institute for Health Surveillance. 2015.

[7] WHO: http://www.who.int/csr/don/21-december-2015-zika-cape-verde/en/

[8] Cape Verde Ministry of Health: https://translate.google.fr/translate?sl=auto&tl=fr&js=y&prev=_t&hl=fr&ie=UTF-8&u=http://www.minsaude.gov.cv/index.php/rss-noticias/919-assessment-of-the-zika-outbreak-situation-in-the-country&edit-text=

Zika Outbreak in French Polynesia, November 2013 – February 2014

French Polynesia (FP) is an overseas collectivity of the French Republic, comprising five archipelagos with 118 islands, 67 of which are inhabited, and a population of 268,270 (2012 census). On October 30, 2013, while FP had been dealing with a dengue epidemic (serotypes 1 and 3) for several weeks, health authorities identified a Zika outbreak for the first time, following reports from several doctors of subfebrile rash syndromes that differed from the usual “dengue-like syndromes.” The outbreak, which began in the Society, Marquesas, and Tuamotu archipelagos, subsequently spread to all the archipelagos. It lasted from October 2013 to April 2014. The final tally shows 8,750 clinically suggestive cases reported by the sentinel physician network, leading to an estimate of 32,000 patients who sought medical care for an infection attributed to the Zika virus (representing approximately 11.5% of the population). Of the 885 cases tested, 43% were confirmed by RT-PCR (383 cases). No deaths related to the infection were reported.

Cases of Zika virus infection were imported into New Caledonia, Easter Island, Japan, mainland France, and Norway following the outbreak in French Polynesia. Since 2014, local transmission has subsequently developed in New Caledonia, the Cook Islands, Easter Island, Vanuatu, and Fiji. In October 2015, Samoa reported a Zika-related outbreak, followed by American Samoa in January 2016.

[9] Note on investigations into congenital brain malformations following the 2013–2014 Zika epidemic.

Outbreaks in New Caledonia, 2014 and 2015

A first Zika virus outbreak occurred in New Caledonia from January to August 2014, following imported cases from Papua New Guinea (late November 2013); 1,400 cases were confirmed by RT-PCR. The Zika virus detected belonged to the same family as the virus that had previously circulated in Asia, thus defining an Asian lineage.

In January 2015, a resurgence of the virus was detected, and the situation became epidemic in May 2015. As of June 12, 2015, 111 locally acquired cases had been biologically confirmed since January 2015. Since June 2015, sporadic cases have been reported regularly.

Outbreak on the island of Yap (Micronesia), 2007

Only 14 human cases had been reported until 2007, the year in which a Zika virus outbreak was described on Yap, in Micronesia. The population of Yap Island is 7,391 (2000 census). Reports of an outbreak of rash-associated syndromes with conjunctivitis and arthralgia, not consistent with dengue, led to the identification of the Asian lineage of the Zika virus as the cause of this outbreak.

A survey conducted from April 1 to July 31, 2007, combined active case finding in healthcare facilities with a seroprevalence study in the general population (a random sample of 200 households). Active case finding identified 185 clinically suggestive and biologically confirmed (RT-PCR or serology) Zika cases in 9 of Yap’s 10 municipalities. The median age was 36 years. The seroprevalence survey estimated the prevalence of antibody-positive patients in the general population aged 3 years and older at 73%, 95% CI [68%–77%]. The proportion of asymptomatic patients was estimated at 81%.