The virus of Zika is the causative agent of fever

Zika virus (ZIKV) is a representative of the viruses of the genus Flavivirus, the family Flaviviridae and belongs to zoonotic arbovirus infections carried by mosquitoes of the genus Aedes. In the human body, this flavivirus causes a disease known as Zik's fever, etiologically related to yellow fever, Dengue fever, West Nile and chikungunya, which also develop due to defeat by flaviviruses.

The Pan American Health Organization (PANO, WHO Regional Office) issued an epidemiological alert on December 1, 2015, to health authorities in the countries of North and Latin America about the spread of the Zik virus in the tropical and subtropical zones of the region.

Structure and life cycle of the virus Zika

The structure of the Zick virus, which refers to RNA-containing noncellular virions, is similar to the structure of all flaviviruses. The Zika virus has a spherical form of nucleocapsid with a diameter of about 50 nm with a membrane-glycoprotein membrane, the surface proteins of which are located in icosahedral symmetry.

Inside the nucleocapsid contains a single-stranded linear RNA encoding the proteins of the virus. A special role is played by the membrane protein E, due to which the nucleocapsids of the virus penetrate into the human cell, attaching to the receptors of their cytoplasmic membranes.

Self-reproduction of viral RNA (replication) occurs on the surface of the endoplasmic reticulum in the cytoplasm of cells infected by the virus. In this case, the virus uses the proteins of the captured host cells to synthesize its polyprotein. And from it, by translating RNA into cellular mRNA during replication, it reproduces the synthesis of its structural and nonstructural nucleoproteins. The release of new virions of the Zick virus occurs when the infected cell (lysis) is killed.

It has been suggested that first the dendritic cells are infected next to the site of the bite (they have infected cell nuclei), and then the infection spreads to the lymph nodes and blood.

The life cycle of this flavivirus takes place in the body of blood-sucking mosquitoes, infected humans and mammals of vertebrates. Human Zick's virus is transmitted as a result of a bite of infected mosquitoes Aedes Albopictus, Aedes Aegypti, Aedes Polynesiensis, Aedes Unilineatus, Aedes Vittatus and Aedes Hensilli. These mosquitoes prefer to live indoors and outdoors near people, their eggs are put in standing water in buckets, animal bowls, flower pots and flower vases, in tree hollows, in piles of rubbish. Insects are very aggressive in the daytime.

Experts believe that mosquitoes become infected when they bite a person already infected with the virus. Mothers infected with the Zika virus can transmit the virus to their infant for some time after infection, causing children to be born with a neurological pathology in the form of a reduction in the size of the skull and brain (microcephaly). In 2015, in 14 states in Brazil, there were 1248 such cases (in 2014 there were only 59 cases).

It is possible that infection occurs through contaminated blood or through sexual contact. In 2009, it was proved that the virus Zika can be transmitted sexually from person to person. Biologist Brian Foy, a specialist in arthropod and infectious diseases from Colorado State University in the United States, was bitten by mosquitoes several times during his visit to Senegal. The fever developed after his return to the States, but before that (even before the onset of the symptoms of the disease) he had an intimate affinity with his wife, who also contracted the fever of Zeke.

To date, the virus ZIKV is being investigated, and experts do not rule out the possibility of catching it with blood transfusions.

Symptoms

The incubation period of infection with the virus Zika varies from 3 to 12 days after the bite of an infected mosquito. And approximately 70% of cases are asymptomatic.

Clinical symptoms of Zick's viruses include:

• minor headaches;
• general malaise;
• itching macular or papular rash on the skin (first the rash appears on the face and then spreads all over the body);
• fever;
• pain in muscles and joints with possible edema of small joints;
• hyperemia and inflammation of the conjunctiva (conjunctivitis);
• pain in the eye area;
• intolerance to bright light.

In rare cases, there are diarrheal symptoms. The first sign of Zika fever is mild headache, fever to + 38.5 ° C and a progressive rash. New rashes last for the first three days, about five days of fever. Then the temperature is normalized, and only the rash remains, which also gradually disappears.

Diagnostics

Diagnosis of Zika fever is based, first of all, on the detection of viral RNA from clinical blood samples of patients.

The main diagnostic methods: the detection of nucleic acids in the serum (in the first three days of the onset of symptoms), as well as in saliva or urine (within the first 3-10 days after symptom onset) - using reverse transcriptase-polymerase chain reaction (PCR).

Serological tests, including immunofluorescence and enzyme immunoassay, can indicate the presence of antibodies IgM and IgG.

Differential diagnosis should take into account the significant similarity of Zik fever to other infectious diseases that develop as a result of mosquito bites in endemic regions:

• fever Dengue,
• chikungunya,
• malaria.

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Treatment

There is no specific treatment for Zeke virus, vaccine or preventive drugs are also not available today.

So, only symptomatic treatment is carried out, mainly aimed at reducing pain and fever - using antipyretic and analgesic agents. Paracetamol is recommended most often: 350-500 mg up to four times a day. The drug can cause side effects in the form of nausea, pain in the stomach, reduce heart rate and sleep disorders. Paracetamol is contraindicated in the case of kidney and liver failure, as well as during pregnancy.

And itching is advised to be removed with the help of antihistamines (Tavegila, Suprastina, etc.). Also, you need to drink more fluids to prevent dehydration.

Specialists of CDC and the American National Center for New and Zoonotic Infectious Diseases (NCEZID) - to avoid the risk of bleeding - do not recommend the use of Aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) until hemorrhagic fever is ruled out.

Prevention

Prevention of infection with the virus Zika includes individual protection against mosquito bites:

• wear clothing that covers the body;
• use repellents;
• Use mosquito nets and screens on windows to prevent mosquitoes from entering the rooms;
• to destroy mosquitoes and the places of their reproduction.

Because mosquitoes of the Aedes family are active during the day, it is recommended that those who sleep during the day (especially small children, sick or elderly) be protected with mosquito nets treated with insecticides.

Most people infected with ZIKV completely recover without serious complications, and to date no deaths have been reported associated with the Zik virus.

The states of Brazil with confirmed reports of the cases of the ZIKV infection virus for 2014-2015, and cases of microcephaly in 2015, as of November 17, 2015.

However, the outlook for the spread of this infection is not very comforting. Until 2007, the virus of Zika gave outbreaks of fever in tropical Africa and in some parts of South-East Asia, after which it spread to some islands of the Pacific region.

In April 2015, the virus was first registered in South America. Zika fever is seen as an intensely spreading infectious disease: its spread has been noted in Brazil, Chile, Colombia, El Salvador, Guatemala, Mexico, Paraguay and Venezuela.

As of the end of January 2016, fever cases have been reported in several European countries: Denmark, Sweden, Germany, Portugal, Finland, Switzerland and England, as well as in the USA.

As noted in the message PANO, the virus Zika can cause congenital malformations in newborns - microcephaly.