In the environment there is a huge amount of viruses. Microorganisms that cannot be seen with the naked eye cause various diseases in humans. Some of the pathogens are even fatal. Quite dangerous is the Zika virus.
Causative agent of the disease
Zika fever is a disease that the virus of the same name causes. He is a representative of the genus Flavivirus. The virus was first discovered in 1947 in the blood of a monkey living in the Zika forest (Uganda). That is why this name was given to the causative agent of fever.
In 1948, scientists discovered Zika virus in mosquitoes that lived in the same forest. Studies that were subsequently carried out by specialists have shown that the pathogen can infect humans. Human infections were detected in 1952 (Uganda and the United Republic of Tanzania).
Fever spread
This disease has been considered harmless for a long period of time. There were no epidemics associated with a disease such as Zika fever. In which countries was the pathogen detected? Antibodies to the virus were found in residents of Africa and Southeast Asia (Egypt, India, Vietnam, Indonesia, CAR, Thailand, etc.). Researchers have become interested in the disease in recent years, when the infection began to spread rapidly beyond its range.
The first outbreak of Zika was recorded on the Yap Islands, located in the Pacific Ocean and part of the Federated States of Micronesia. After laboratory studies, 49 cases of infection were confirmed. A few years later, another outbreak was recorded in French Polynesia. In 2013-2014, 32 thousand people were examined. The national surveillance system has recorded more than 8 thousand suspected cases of the disease. Of these, 383 people were confirmed to have BVVZ (Zika virus disease) after laboratory tests.
In 2014, the disease came to South America. Zika was diagnosed with Easter Island residents. After about a year, the RNA of the pathogen was detected in people living in the north-eastern part of Brazil. From January 2015 to February 2016, virus infections were reported in 44 countries. BVVZ has become a global problem.
The first case of Zika fever in Russia
In Australia, China, Japan, Canada, and Europe, only “imported” cases are reported. In Russia, too, a case of the importation of Zika fever by a tourist who returned to his homeland was recorded. A woman (age 36 years) rested in the Dominican Republic from January 27 to February 3, 2016. Several times she was bitten by mosquitoes, which caused the disease.
Zika's fever appeared on the day of return. The tourist felt weakness, discomfort in her stomach. Arriving in Russia, she began to notice the following symptoms: loose stools, headaches, rash on her chest and arms, fever. A few days after returning, the woman was hospitalized in a state of moderate severity. Doctors noted her hyperemic oropharynx, a small rash on her face, trunk and limbs, an increase in cervical lymph nodes, an increase in body temperature to 38 degrees.
Existing symptoms have allowed doctors to suggest the presence of one of such diseases as dengue fever and Zika fever. Treatment could only be prescribed after an accurate diagnosis. For this, specialists took urine and blood samples for laboratory analysis. In the course of the research, Zika virus RNA was detected.
Pathogen transmission through bites
The carriers of the virus are mosquitoes of the genus Aedes (Ae. Africanus, Ae. Aegypti, Ae. Albopictus). The pathogen enters the body of insects after being bitten by sick primates. How monkeys become infected is a question that modern science cannot give an answer to. The reservoir of the virus in nature is unknown.
In humans, Zika fever occurs after sucking infected mosquitoes. At the time of a bite, viruses penetrate the human body, spread through it with a blood stream through the vessels. This pathway is called transmissible.
Sexually transmitted virus
In people infected with Zika, the pathogen was found not only in plasma and blood serum, but also in semen, vaginal secretions. This fact allowed experts to assume that the transmissible transmission path is not the only one. The virus can enter the body of a healthy person during intimacy with the patient.
Sexually transmitted Zika fever has been reported in France, Italy, USA, New Zealand, Argentina. The causative agent of the disease is also detected in the saliva, urine of sick people. However, there is currently no evidence to support the possibility of transmission of the virus through contact with these biological fluids.
Transmission of the virus to the fetus during pregnancy or childbirth
Zika fever can be transmitted to the baby during pregnancy or childbirth. Vertical transplacental spread of the virus provokes intrauterine infection and the occurrence of malformations. Infection during childbirth causes a congenital infection.
Intrauterine infection can lead to:
- damage to the central nervous system;
- fetal growth retardation;
- placental insufficiency;
- death of the fetus.
With Zika fever in early pregnancy, the likelihood of developing microcephaly is high. By this term, specialists understand the too small size of the skull and brain. In children with this complication, the head does not grow after birth. Microcephaly is a rather rare condition. However, in 2015-2016, the number of children born with this pathology significantly increased. This is due to Zika fever. During this period, more than 5 thousand cases of the birth of babies with microcephaly from mothers infected with the virus were recorded.
Symptoms of the disease
After the bite of a mosquito, which is the carrier of the virus, the incubation period begins. Its duration can be from 3 days to 2 weeks. After the incubation period, the first symptoms occur. It is worth noting that the clinical manifestations of the disease develop only in 20-25% of infected individuals. In order for doctors to suspect an illness such as Zika fever, the following symptoms should be observed:
- a single increase in body temperature;
- rashes on the trunk and limbs;
- joint pain;
- inflammation of the mucous membrane of the eyes.
Some patients complain of pain in the muscles and abdomen, rapid and repeated loose stools, nausea, and skin itching. However, the listed symptoms with Zika fever are extremely rare.
Diagnostics
Plasma and blood serum, saliva, urine, sperm - a material suitable for the detection of a disease such as Zika fever. Diagnosis, if necessary, can be carried out by cerebrospinal and amniotic fluids, umbilical cord blood. At the death of the person being examined, samples of internal organs (tissue of the liver, kidneys, brain, lungs) are studied.
Basically, specialists only carry out blood sampling. This procedure is performed in the morning. Blood in a volume of 3-4 ml is taken into a test tube with an anticoagulant. Then it is centrifuged to obtain a plaza. Experts store the resulting sample before polymerase chain reaction (PCR):
- no more than 5 days at a temperature of plus 4-8 degrees Celsius;
- within 1 year at a temperature of minus 6-20 degrees;
- over a long period of time at a temperature of –70 degrees Celsius.
Blood serum is obtained by standard methods. It is stored until serological and molecular genetic diagnostic studies are performed in the same modes as plasma.
Diagnosis is usually carried out on the 5-7th day of the disease and after 7-10 days. In the first week of the disease by the method of polymerase chain reaction (PCR) in the taken blood samples, Zika fever virus is detected - or rather, its RNA. IgM antibodies are detected at approximately 5–6 days of fever. By the end of the second week of the disease, IgG antibodies appear in the blood of infected people.
Fever treatment
In all countries of the world, with the exception of Russia, hospitalization of people with symptoms of a disease caused by Zika virus is carried out only if there are clinical indications. In the Russian Federation, everything is different. All patients with suspicious symptoms are hospitalized in an infectious diseases hospital, where they undergo examinations.
Zika fever, the symptoms of which manifested itself, proceeds, as a rule, in a mild form. Doctors prescribe antipyretics to patients, recommend a lot of rest and drink more fluids. Etiotropic therapy that can eliminate the cause of Zika fever does not exist. Research institutes and international companies are working on the development of antiviral drugs. However, it has not yet been possible to develop such a product that could destroy the pathogen in the human body.
Particularly noteworthy is the management of pregnant women with Zika fever. When diagnosing this disease, women in position are not recommended to prescribe acetylsalicylic acid. In the first trimester of pregnancy, a comprehensive examination is necessary. Ultrasound is performed, methods of invasive prenatal diagnosis are used. The results obtained allow us to resolve the issue of maintaining pregnancy.
Possible complications
In 2015, a BVVZ outbreak in Brazil was recorded. Experts who assessed the situation noted that with the increase in the number of infected, the number of patients with Guillain-Barré syndrome increased. This is a condition in which the human immune system affects the peripheral nervous system.
In most cases in humans, Guillain-Barré syndrome is mild. Patients report weakness and tingling in their lower and upper limbs. Some people experience paralysis of the legs, arms, and facial muscles. In severe cases, Guillain-Barré syndrome leads to paralysis of the respiratory muscles, cardiac arrest. The result is death.
Patients with Guillain-Barré syndrome caused by Zika fever should be closely monitored (monitoring of blood pressure, heart rate, respiration is necessary). That is why sick people are hospitalized even with a mild course of this complication.
Preventative measures
In order not to encounter a disease such as Zika fever, prevention should be as follows:
- People choosing a place to stay abroad should pay attention to countries that are epidemiologically safe.
- If the vacation is planned in a country where mosquitoes are the sources of fever, it is recommended to take repellents with you. To protect against insects, you can use light clothing that covers most of the body.
- Do not open windows in hotels unless they are equipped with mosquito nets.
- You should also avoid visiting wetlands. Water containers (car tires, flower pots) should be emptied and cleaned (or covered with something), because mosquitoes love a humid and cool atmosphere.
Do not forget that BVVZ can be transmitted sexually. Upon returning from rest for 8 weeks (in the absence of symptoms), you should adhere to safe sexual behavior (use condoms or avoid intimate contacts). When the first signs of the disease appear, such a lifestyle will have to be conducted for 6 months (at least).
In conclusion, it is worth noting that Zika fever (clinic, epidemiology, treatment and prevention of this disease) is a hot topic. An illness that has not been taken seriously for a long period of time has in recent years become a threat to the health and life of most of the world's inhabitants. Currently, BVVZ is not yet fully understood: all the complications that may arise due to the pathogen are not known, vaccines and drugs against the virus have not been developed. Perhaps these issues will be resolved in the near future, because international organizations and research institutes are just working in these areas.