Zika fever is an acute infectious disease with a predominantly transmissible mechanism of transmission. The disease is asymptomatic or manifests itself as an increase in body temperature, general intoxication syndrome, pain in muscles, joints, conjunctivitis, rash. The main danger of infection is the formation of microcephaly and various neurological disorders in the fetus in case of infection of pregnant women, as well as persistent CNS pathologies in adults. Diagnostics is based on the detection of the virus itself in biological material, as well as specific antibodies in human serum. Etiotropic treatment has not been developed. Symptomatic therapy is being carried out.
For the first time, the virus was isolated from the blood of a monkey that lived in the Zika forest in Uganda. Translated from the local dialect “zika” means “thickets”. The endemic territories for this infectious disease are the countries of Central and South America, Africa, Southeast Asia, the Pacific Islands. In other states, cases of infection have also been reported, but they are due to imported cases among travelers. Since 2015, about 4 million cases have been recorded. In 2016, WHO declared an international health emergency due to an outbreak. Such alertness is associated with the pronounced teratogenic effect of the virus and the lack of specific treatment.
The susceptibility is universal. Seasonality is not pronounced, however, there is an increase in infection cases during heavy rains, which is associated with an increase in the activity of mosquito vectors. With the development of global warming, the distribution area of the corresponding insects increases, which creates an even greater danger to humans. However, the virus cannot stand cold temperatures. Therefore, the formation of persistent foci of fever in countries with a temperate climate is impossible, but imported cases can contribute to the development of outbreaks in summer.
Causes of Zika Fever
The causative agent of the disease is an RNA-containing virus from the Flaviviridae family. Refers to arbovirus. The pathogen is fairly stable in the environment. In a lyophilized state, it lasts up to 30 months. Phenol and low-percentage ethyl alcohol do not kill the microorganism, however, it is quickly inactivated upon contact with ether, a solution of potassium permanganate. There are two lines of the virus: Asian and African. It is believed that the African form parasitizes monkeys, while humans are a casual host. The Asian line is isolated from the majority of patients during epidemics in endemic areas.
The source of infection is monkeys and a sick person. The transmission of the disease is realized through a transmission mechanism using the Aedes mosquito. Possible sexual, parenteral (with transfusion of blood components), transplacental, contact (with saliva) routes of infection. The sexual route is realized only in men. Some authors express the possibility of aspiration infection in persons with immunodeficiency. The virus is found in blood, saliva, urine, semen, breast milk, amniotic fluid during intrauterine infection. The danger is the transmission of the Zika virus during blood transfusions and organ and tissue transplants, since in most cases the disease is asymptomatic, there is no specific donor screening, which can lead to iatrogenic infection of recipients.
The mechanism of development of this infectious disease is not fully understood. It is believed that dendritic cells are affected first at the site of the bite. Further, the virus with the blood stream spreads to various organs and tissues. In infected cells of the human body, RNA replicates. During the release of new virion particles from the cell, cytolysis of the affected structures develops. When studying microslides, morphological changes in skeletal muscles, myocardium (swelling of fibers, necrosis, proliferation of nuclei, disappearance of transverse striation) were found. In experiments on laboratory animals, the high tropism of the virus to the cells of the nervous system has been proven. In the case of intrauterine infection, the pathogen affects the chorionic villi, placental vessels. Persistent fetal ischemia occurs. In addition, the Zika virus affects the mitotic activity of cells, which in turn leads to the formation of malformations.