ZIKA VIRUS DISEASE

ZiKa Virus (ZKV)disease is an emerging mosquito-borne human viral infection that has been ecologically associated with congenital microcephaly in newborns in Brazil. The general public is therefore advised to take precautions to reduce the risk of infection for example: protecting yourself from mosquito bites by wearing long-sleeved shirts and trousers and keeping doors and windows screened. Pregnant women are advised to: prevent contact with people traveling from Brazil showing signs of fever/infection, use pregnancy compatible mosquito repellents and avoid environmental exposures to chemicals or consumption of teratogenic drugs.

Congenital microcephaly means the newborn’s head falls below its normal circumference for its gestational age, sex and race. The small head is the result of a neurodevelopmental disorder and can be monitored prenatally using ultrasound machines.

Epidemiology

The virus (ZKV) was first isolated in Uganda in 1947 and has since been reported in tropical areas of western Africa (Nigeria, Sierra Leone, Ivory Coast, Cameroon and Senegal) and of central Africa (Gabon, Uganda and Central African Republic), in Asia (Pakistan, Indonesia, Philippines, Malaysia, Cambodia and Thailand) and in several islands of the pacific region since 2007 (Micronesia, Cook Islands, French Polynesia, New Caledonia, Guam, Samoa, Vanuatu and Solomon Islands). The latest (2014) cases of ZKV infection have been reported in the Americas (North-eastern Brazil in the states of Bahia, Maranhao, Pernambuco, Rio Grande do Norte, Paraíba and Sergipe). A total of 14835 cases of acute exanthematous illness have been reported in 12 health districts of Salvador – the third city of Brazil – between 15 February 2015 and 25 June 2015 with an overall attack rate of 5.5 cases/10 000 inhabitants). The expansion of the ZIKV infections to South America constitutes a significant development in the epidemiology of this emerging vector-borne disease.

Etiology

ZKV dis is caused by Zika virus (ZIKV), a flavivirus from the Flaviviridae family and Spondweni serocomplex. The virus was first identified in 1947 in the Zika forest in Uganda in the rhesus macaque population.

Transmission

Mosquitoes remain the main transmitters of the disease with the Aedes mosquitoes (Aedes aegypti, Aedes hensilii and Aedes albopictus) being highly implicated.

There is also evidence that prenatal transmission can occur via the placenta or during the delivery of a viraemic mother. ZIKV transfusion-derived transmission is theoretically possible. Possible cases of sexual transmission of ZIKV have been reported but these three modes of transmission are rare.

Symptoms

The incubation period of the infection ranges from 3 to 12 days. The disease symptoms are usually mild and last for 2 to 7days. Infection may go unrecognized or be misdiagnosed as dengue, chikungunya or other viral infections giving fever and rash. Asymptomatic infections are common and only one in four people infected with ZIKV are believed to develop symptoms.

The main symptoms of ZIKV disease include:

  • low-grade fever (<38.5°C)
  • transient arthritis/arthralgia with possible joint swelling mainly in the smaller joints of the hands and feet.
  •  maculo-papular rash often spreading from the face to the body
  • conjunctival hyperaemia or bilateral non-purulent conjunctivitis (Red eyes)
  • General non-specific symptoms such as myalgia (muscle pains), asthenia and headaches.

Association with neurological complications is still under investigation ad there has however been no deaths associated with ZKV infection to date.

Dr. Moses Bwana

Post-grad at the University of Nairobi [Applied Microbiology]

Department of Pathology, Microbiology and Parasitology

Faculty of Veterinary Medicine

Cell: +254729246187; Email: bwanamoses@gmail.com

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