The first case of West Nile virus infection this year was confirmed by the health authorities in a patient from the Capital. Such cases are registered every summer, experts say.
Mosquitoes are the ones that transmit the West Nile virus PHOTO: Pixabay
Diseases caused by contact with viruses considered characteristic of other continents have been more and more common in Europe in recent decades. Responsible for these diseases are parasites from the group of mosquitoes or ticks.
The category of these “exotic” diseases also includes the infection caused by the West Nile virus, state the sanitary-veterinary authorities in an informative material on the ANSVSA website.
What is West Nile virus infection. Since it is under surveillance in Romania
West Nile virus infection is a disease that predominantly develops as a meningoencephalitis. Mosquitoes are the vectors that transmit the disease, which belongs to the group of zoonoses, being common to humans and animals.
The disease particularly affects domestic and wild birds, as well as several species of mammals, the most exposed being equids (horses) and humans.
“The involvement of a virus in the transmission of the disease to humans was demonstrated in 1937, in the West Nile district of Uganda (Africa), following the testing of blood samples collected from a patient who had a febrile syndrome. In animals, the disease was first diagnosed in 1956 in Egypt (in horses). It is important to note the situation encountered in North America, where the virus was reported for the first time in 1999, currently the disease is found throughout the North American continent (the term used in this case being endemic disease – permanent in a certain territory ). In 1996, Romania faced the largest West Nile meningitis epidemic in Europe. Since 1997, the health authorities have implemented a surveillance system for this infection so that all cases of meningitis are strictly monitored by doctors”. specify the specialists, in the cited document.
How the disease is transmitted
The West Nile virus that causes the disease is transmitted from animals to humans through mosquito bites, which is why it is extremely important to take action to avoid these bites. Research has shown that infected birds are those that have the virus in their blood in large enough quantities for the mosquito to become infected.
Specialists explain how the disease is actually transmitted. The main condition is that the mosquito feeds on blood from an already infected animal, because the virus in animals, in the initial phase of the disease, is found in the circulatory system.
“Once inside the digestive system, the virus will be multiplied by the cells, finally locating in the mosquito’s salivary glands. At this stage the vector becomes capable of transmitting the disease if it feeds on a healthy receptive (susceptible) animal. From the research carried out so far, it has been found that birds are the only animals in whose blood the virus is found in large enough quantities for the mosquito to become infected. The blood of horses and humans also represents a favorable environment for the multiplication of the infectious agent, but the amount of circulating virus is not high enough and thus, by feeding, the mosquito does not become infected”, it is mentioned in the article posted on the ANSVSA website.
The disease is maintained in nature by repeating a cycle of mutual contamination between the mosquito and the various species of domestic and wild birds on the territory of a locality or a county. Occasionally, when mosquitoes intervene in the cycle that can feed on both birds and mammals, cases of illness in humans or horses can also occur, the specialists explain.
Migratory birds have a decisive role in the introduction of the disease in various territories around the globe.
How the disease manifests itself in humans, how it manifests itself in animals
It should be noted that in a small percentage of cases of infection in humans, serious forms of the disease are reached, accompanied by symptoms that send us urgently to the doctor, in most cases passing over the infection without symptoms.
The virus has an affinity for nerve cells in the brain, spinal cord, nerves, etc., experts say, but the clinical manifestations differ in humans compared to animals.
“In humans, the most common symptoms are: fever (38˚ – 40˚C), headache, neck, muscle and joint pain, lack of appetite, nausea, conjunctivitis. Diarrhea or respiratory signs may even occur. The symptoms are similar to seasonal flu. In certain cases (1 in 150 infected people) the disease can evolve into more serious forms such as encephalitis, meningitis, meningoencephalitis or even poliomyelitis”, it is mentioned in the cited article. Children and the elderly are the most affected categories.
Infected animals can also show symptoms. “In horses, the disease generally evolves asymptomatically. However, approximately 1 in 10 infected horses may show signs that demonstrate damage to the spinal cord and brain functions: loss of balance, instability, paresis, paralysis, deviation alternating with bouts of aggression, exaggerated reaction to noise, light, uncontrolled movements, etc. Mortality can reach up to 40-60% of affected horses”, ANSVSA specialists explain.
In the case of birds, the reaction is different. Some species may have no symptoms, while others may show signs such as: deviation, weight loss, ruffled feathers, inability to fly, head thrown back, balance disturbances in walking, “pedaling” movements of the legs. Typically, death occurs in 25-40% of birds within 24 hours of the appearance of nervous signs.
DSVSA specialists advise us, considering the potential danger to humans, to report to the authorities when we observe bird corpses or birds that move with difficulty, cannot fly or stay motionless on the ground, the information received from the population helping veterinarians and humans in the rapid adoption of the necessary measures to reduce the possibility of an eventual disease outbreak.
How can we prevent West Nile virus infections?
Preventive measures for West Nile virus infections are actually aimed at preventing mosquito bites, given how the disease is transmitted. Therefore, we will mainly take care to eliminate the favorable conditions for the development of mosquitoes. In the urban environment, the actions are those of disinsection, but where animals are raised, other measures must be adopted, such as:
– covering the waterers during the day (if the animals are used for work or grazing) but also during the night, after watering;
– removal of temporary water accumulations inside or around the farm or house (resulting from summer rains).
To prevent the transmission of the disease to humans, the usual measures to remove mosquitoes from inside homes prove to be the most effective:
– installing mosquito nets on the windows;
– the use of commercially available repellent chemical substances;
– the use of long pants and long-sleeved clothes after dark.
“Not everyone who comes into contact, or who is bitten by these mosquitoes, also manifests the disease”
The primary infectious disease doctor Simina Aysel Florescu explained, in a live intervention on Digi 24, that these cases of infection are no longer a novelty in Romania.
“It is good not to generate any kind of panic now, because it has been known for a very long time that in Romania, and especially in the south of the country, including Bucharest, this virus has been present for a long time and is transmitted by mosquitoes existing in the country ours for many years. This thing happens every summer. The fact that there is surveillance of the transmitting vectors is a very good thing, because that way we can act”explained Dr. Florescu.
It is important to act in such a way as to avoid infections. On the other hand, the doctor emphasized, not all people who are bitten by the virus-carrying mosquito manifest the disease.
“Not everyone who comes into contact, or who is bitten by these mosquitoes, also develops the disease or severe forms of the disease. Because those who take serious forms are in a very small percentage, a few percent. A maximum of 10% of those infected develop clinically evident forms with fever and of these even fewer develop severe forms of meningo-encephalitis. (…) On the other hand, if, especially in the elderly, the signs that I talked about before appear (n. ed. – headache, severe headaches, fever and possibly muscle pains), obviously they reach the attention of the hospital where we can determine with certainty whether they have this disease or not. It is very important, it is mandatory to talk to a doctor”, Dr. Simina Aysel Florescu insisted. The doctor also stated that it is important to prevent infection by acting against the vectors of the disease (mosquitoes) because there is no vaccine for prevention.
