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Factsheet for health professionals

Last reviewed/updated on: 08.03.2016

Disclaimer: The information contained in this factsheet is intended for the purpose of general information and should not substitute individual expert advice and judgement of healthcare professionals.  

Introduction 

Zika virus disease is a mosquito-borne disease caused by Zika virus which causes in general a mild febrile illness with maculo-papular rash. Aedes mosquitoes are considered as main vectors. Before 2007, viral circulation and a few outbreaks were documented in tropical Africa and in some areas in Southeast Asia. Since 2007, several islands of the Pacific region have experienced outbreaks.
In 2015, Zika virus disease outbreaks were reported in South America for the first time. Zika virus disease is now considered as an emerging infectious disease.
 
A significant increase of patients with Guillain–Barré syndrome (GBS) was reported during the 2014 outbreak in French Polynesia and the Americas since 2015. A similar increase along with an unusual increase of congenital microcephaly was observed in some regions in north eastern Brazil in 2015. Causal relationships are currently under investigation.

There is no prophylaxis, treatment or vaccine to protect against Zika virus infection. Therefore, preventive personal measures are recommended to avoid mosquito bites during the daytime.
 

The pathogen 

  • Zika virus disease is caused by a virus from the Flavivirus genus, Flaviviridae family, from the Spondweni group.
  • It was first isolated in 1947 from a monkey in the Zika forest, Uganda, then in mosquitoes (Aedes africanus) in the same forest in 1948, and in a human in Nigeria in 1952. There are two Zika virus lineages: the African lineage and the Asian lineage which has recently emerged in the Pacific and the Americas. [1,2]

 

Clinical features and sequelae

  • The incubation period ranges between approximately three to 12 days after the bite of an infected mosquito.
  • Most of the infections remain asymptomatic (approximately 80%).
  • Disease symptoms are usually mild and the disease in usually characterised by a short-lasting self-limiting febrile illness of 4–7 days duration without severe complications, with no associated fatalities and a low hospitalisation rate.
  • The main symptoms are maculopapular rash, fever, arthralgia, fatigue, non-purulent conjunctivitis/conjunctival hyperaemia, myalgia and headache. The maculopapular rash often starts on the face and then spreads throughout the body. Less frequently, retro-orbital pain and gastro-intestinal signs are present.

 

Congenital central nervous system malformationsmalformations such as  microcephaly in foetuses and newborns from mothers possibly exposed to Zika virus during  pregnancy were notified during recent Zika disease outbreaks (French Polynesia and Brazil). Unusual increases of Guillain–Barré syndrome were reported in several countries in the Americas and French Polynesia coinciding with the Zika virus outbreak.

Further evidence is needed to establish a causal link between Zika virus infection and these neurological/neurodevelopmental impairments or auto-immune conditions.
 

Epidemiology 

  • Serological surveys in Africa and Asia indicate a most likely silent Zika virus circulation with detection of specific antibodies in various animal species (large mammals such as orangutans, zebra, elephants, water buffaloes) and rodents.
  • The knowledge of geographical distribution of Zika virus is based on results of serosurveys and viral isolation in mosquitoes and humans, and with reports of travel-associated cases. Before 2007, the areas with reported Zika virus circulation included tropical Africa and Southeast Asia. Very few outbreaks were documented prior to 2007.
  • An outbreak was reported on Yap Island, Federated States of Micronesia from April to July 2007 [3]. This was the first outbreak of Zika virus identified outside of Africa and Asia. Between 2013 and 2015, several significant outbreaks were notified on islands and archipelagos from the Pacific region including a large outbreak in French Polynesia. In 2015, Zika virus emerged in South America with further spread across the Americas [1,4,5]. 

 

Transmission 

  • Zika virus is transmitted by mosquitoes. It has been isolated from Aedes aegypti mosquitoes and experimental infections show that this species is capable of transmitting Zika virus.
  • Other Aedes mosquito species (notably Ae. africanusAe. albopictusAe. polynesiensisAe. unilineatus, Ae. vittatus and Ae. hensilli) are considered as potential vectors of Zika virus. These species bite during the day.
  • Additional modes of transmission have been identified. Perinatal transmission can occur most probably by trans-placental transmission or during delivery when the mother is infected. Sexual transmission was reported in a few instances.
  • There is a potential risk of Zika virus  transmission from a blood transfusion.
  • More information on mosquitoes can be found here: Aedes albopictus and Aedes aegypti. [1,6-8]

 

Diagnostics 

  • Zika virus disease diagnostics is primarily based on detection of viral RNA from clinical specimens in acutely ill patients.
  • The viraemic period appears to be short, allowing for direct virus detection during the first 3–5 days after the onset of symptoms. Zika virus RNA has been detected in urine up to 10 days after onset of the disease.
  • From day five post onset of disease, serological investigations can be conducted by detection of Zika-specific IgM antibodies and confirmation by neutralisation, seroconversion or four-fold antibody titer increase of Zika specific antibodies in paired serum samples.
  • Serological results should be interpreted according to the vaccination status and previous exposure to other flaviviral infections.

 

Case management and treatment 

  • There is no vaccine or specific prophylactic treatment.
  • Differential clinical diagnostic should be considered as well as co-infection with other mosquito-borne diseases such as dengue fever, chikungunya and malaria.
  • The treatment is symptomatic and mainly based on pain relief, fever reduction and anti-histamines for pruritic rash.
  • Treatment with acetylsalicylic acid and no-steroidal anti-inflammatory drugs was discouraged because of a potential increased risk of haemorrhagic syndrome reported with other flaviviruses as well as the risk of Reye's syndrome after viral infection in children and teenagers.

 

Public health control measures

  • No vaccine or prophylactic treatment is available.
  • Integrated vector management aiming to reduce mosquito vector density in a sustainable manner is of primary importance. Intersectoral collaboration and efficient public communication strategies to ensure community participation are required for sustainable vector control program.
  • Activities supporting the reduction of mosquito breeding sites in outdoor/indoor areas by draining or discarding sources of standing water at the community level include:
      • removal of all open containers  with stagnant water in and surrounding houses on a regular basis (flower plates and pots, used tyres, tree-holes and rock pools), or, if that is not possible, treatment with larvicides),
      • tight coverage of water containers, barrels, wells and water storage tanks,
      • wide use of window/door screens by the population.
  • During an outbreakelimination of adult mosquitoes through aerial spraying with insecticides can be considered.
  • More information on mosquitoes can be found here:  Aedes albopictus and Aedes aegypti. 

 

Infection control, personal protection and prevention 

  • Prevention is also based on protection against mosquito bites. Aedes mosquitoes bite during the daytime both indoors and outdoors. Therefore personal protection measures should be applied during the day .
  • Personal protection measures to avoid mosquito bites should be applied when in risk areas by:
    • using appropriate mosquito repellents and wearing long-sleeved shirts and long trousers especially during the hours of highest mosquito activity,
    • sleeping or resting in screened or air-conditioned rooms, otherwise use insecticidal treated mosquito nets, even during the day,
    • removing mosquito breeding sites in close outdoor/indoor premises.
  • Use mosquito repellent in accordance with the instructions indicated on the product label.
  • Travellers with immune disorders or severe chronic illnesses should consult their doctor or seek advice from a travel clinic before travelling, particularly on effective prevention measures.
  • Similar protective measures apply to a symptomatic patient in order to prevent transmitting the disease to non-infected mosquitoes.
  • More information on mosquitoes can be found here: Aedes albopictus and Aedes aegypti.
 

List of references        

1.         Hayes EB. Zika virus outside Africa. Emerg Infect Dis. 2009 Sep;15(9):1347-50.
2.         Faye O, Freire CC, Iamarino A, Faye O, de Oliveira JV, Diallo M, et al. Molecular Evolution of Zika Virus during Its Emergence in the 20(th) Century. PLoS Negl Trop Dis. 2014;8(1):e2636.
3.         Duffy MR, Chen TH, Hancock WT, Powers AM, Kool JL, Lanciotti RS, et al. Zika virus outbreak on Yap Island, Federated States of Micronesia. N Engl J Med. 2009 Jun 11;360(24):2536-43.
4.         Cristiane WC, Igor ADP, Mariana K, Moreno SR, Monaise MOS, Gubio SC, et al. Outbreak of Exanthematous Illness Associated with Zika, Chikungunya, and Dengue Viruses, Salvador, Brazil. Emerging Infectious Disease journal. 2015;21(12):2274.
5.         Musso D, Nilles EJ, Cao-Lormeau VM. Rapid spread of emerging Zika virus in the Pacific area. Clin Microbiol Infect. 2014 Oct;20(10):O595-6.
6.         Diallo D, Sall AA, Diagne CT, Faye O, Faye O, Ba Y, et al. Zika virus emergence in mosquitoes in southeastern Senegal, 2011. PLoS One. 2014;9(10):e109442.
7.         Li MI, Wong PS, Ng LC, Tan CH. Oral susceptibility of Singapore Aedes (Stegomyiaaegypti (Linnaeus) to Zika virus. PLoS Negl Trop Dis. 2012;6(8):e1792.
8.         Wong PS, Li MZ, Chong CS, Ng LC, Tan CH. Aedes (Stegomyiaalbopictus (Skuse): a potential vector of Zika virus in Singapore. PLoS Negl Trop Dis. 2013 Aug;7(8):e2348.
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