ZIKV Transmission Documented in 55 Countries and Territories
Posted by feww on March 9, 2016
Geographical distribution of Zika virus steadily widening
A total of 55 countries and territories have documented Zika virus transmission between 1 January 2007 and 3 March 2016.
- Colombia reported 42,706 suspected cases of ZIKV btween 1 October 2015 and 20 February 2016, with 1,612 cases confirmed.
- Starting 2007, locally acquired Zika cases have been reported in 15 countries and territories in the Western Pacific Region.
- Four Pacific Island countries and areas (American Samoa, Marshall Islands, Samoa and Tonga) have reported Zika infections in 2016.
- Nauru has declared Zika virus as a national emergency of concern for purposes of preparedness, but to date no Zika virus cases have been reported.
- Between 1 October 2015 and 7 February 2016, Cabo Verde (African region), reported 7,325 suspected cases of Zika virus disease (two cases have been confirmed, so far).
- The outbreak peaked during the week of 22 November 2015 and has been in decline since then; 44 cases were reported in the week up to 21 February 2016. The number of suspected cases of Zika virus disease reported each week in Praia (light blue) and other municipalities (dark blue) of Cabo Verde (Fi g. 4).
- The outbreak appears to have begun in Praia and then spread to other municipalities. Preliminary information, subject to confirmation, indicates that this outbreak has been caused by an African strain of Zika virus.
- No neurological abnormalities have been reported.
Incidence of microcephaly
- Between 22 October 2015 and 27 February 2016 a total of 5,909 cases of microcephaly and/or central nervous system (CNS) malformation were reported by Brazil including 139 deaths including miscarriage or stillbirth. [Previously an average of 163 microcephaly cases was recorded nationwide.]
- 31 of these were confirmed as having microcephaly and/or CNS malformation potentially linked to congenital Zika virus infection, 96 remain under investigation and 12 were discarded.
- The reported increase in microcephaly incidence in Brazil is concentrated in the Northeast Region.
- An outbreak of Zika virus in French Polynesia was followed by an increase in the number of CNS malformations in children born between March 2014 and May 2015. A total of 19 cases were reported including eight microcephaly cases compared to the national average of 0 – 2 cases per year.
- Zika virus is not yet proven to be a cause of the increased incidence of microcephaly in Brazil. However, (i) given the temporal and geographical associations between Zika virus infections and microcephaly, (ii) the repeated discovery of virus in fetal brain tissue, and (iii) in the absence of a compelling alternative hypothesis, a causal role for Zika virus is a strong possibility that is under active investigation, says WHO.
Incidence of Guillain – Barré syndrome (GBS)
In the context of Zika virus circulation, nine countries or territories have reported increased GBS incidence and/or laboratory confirmation of a Zika virus infection among GBS cases.
- Reported increase in incidence of GBS cases, with no GBS cases biologically documented of Zika virus infection: El Salvador and Colombia.
- Reported increase in incidence of GBS cases, with at least one GBS case confirmed with previous Zika virus infection: Brazil, French Polynesia, Suriname and Venezuela.
- No increase in GBS incidence reported but at least one GBS case confirmed with previous Zika virus infection: Martinique, Panama and Puerto Rico.
Between October 2013 and April 2014, French Polynesia experienced the first Zika virus outbreak ever recorded in the country. During the outbreak, 42 patients were admitted to hospital with GBS. This represents a 20 – fold increase in incidence of GBS in French Polynesia compared with the previous four years.
- Of the 42 patients, 16 (38%) required admission to an intensive care unit and 12 (29%) received mechanical ventilation. No deaths were reported.
- The majority of these cases (88%) reported symptomatic Zika virus infection in the days that preceded the onset of neurological symptoms. A recently published formal analysis of these data (case – control study) showed a strong association between Zika infection and GBS .
- This study is the first large observational study to compare exposure to Zika virus among people with and without GBS and provides important information about the causal role of Zika infection.
- In 2015 in the state of Bahia in Brazil, 42 GBS cases were reported, among which 26 (62%) had a history of symptoms consistent with Zika virus infection. A total of 1,708 cases of GBS were registered nationwide, representing a 19% increase from the previous year (1,439 cases of GBS in 2014), though not all states reported an increase in incidence.
- In Colombia, 201 GBS cases with a history of suspected Zika virus infection were reported in the nine weeks to 14 February 2016. Most of the cases are from Norte de Santander and Barranquilla – areas where many of the Zika virus cases have been registered.
- To date, none of the cases of GBS have been laboratory confirmed for Zika virus infection, or other possible causes, and the patterns of infection and disease by age and sex need confirmation.
Additional information [sourced from who]
Zika virus disease is caused by a virus transmitted by Aedes mosquitoes. Other transmission modes are still under investigation. People with Zika virus disease usually have a mild fever, skin rash (exanthema), and conjunctivitis. These symptoms normally last f or 2 – 7 days. At present there is no specific treatment or vaccine currently available. The best form of prevention is protection against mosquito bites. Zika virus is known to circulate in Africa, the Americas, Asia, and the Pacific region. Zika virus had only been known to cause sporadic infections in humans until 2007, when an outbreak in Micronesia infected 31 people.
Microcephaly is an uncommon condition where a baby’s head circumference is less than expected based on the average for their age and sex. The condition is usually a result of the failure of the brain to develop properly, and can be caused by genetic or environmental factors such as exposure to toxicins, radiation, or infection during development in the womb. Microcephaly can be present as an isolated condition or may be associated with other symptoms such as convulsions, developmental delays, or feeding difficulties.
Guillain – Barré syndrome
Guillain – Barré syndrome in its typical form is an acute illness of the nerves that produces a lower, bilateral, and symmetrical sensorimotor development deficit. In many cases there is a history of infection prior to the development of the Guillain – Barré syndrome. The a nnual incidence of GBS is estimated to be between 0.4 and 4.0 cases per 100,000 inhabitants per year. In North America and Europe GBS is more common in adults and increases steadily with age. Several studies indicate that men tend to be more affected than women.
Resources from WHO
Microcephaly http://www.who.int/emergencies/zi ka – virus/microcephaly/en/
Guillain – Barré syndrome http://www.who.int/mediacentre/factsheets/guillain – barre – syndrome/en/
Infants with microcephaly http://www.who.int/csr/resources/publications/zika/assessment – infants/en/
Guillain – Barré syndrome http://www.who.int/csr/resources/publications/zika/guillain – barre – syndrome/en/
Sexual transmission http://who.int/csr/resources/publications/zika/sexual – transmission – prevention/en/
Vector control http://www.who.int/emergencies/zika – virus/articles/mosquito – control/en/
Blood safety http://who.int/csr/resources/publica tions/zika/safe – blood/en/index.html