West Nile Fever: Symptoms

The incubation period of the western Nile fever lasts from 2 days to 3 weeks, usually 3-8 days. Symptoms of the western Nile fever start acutely with an increase in body temperature to 38-40 ° C, and sometimes even higher for several hours. The fever is accompanied by severe chills, intense headache, pain in the eyeballs, sometimes vomiting, pains in the muscles, lower back, joints, a sharp general weakness. Intoxication syndrome is expressed even in cases that occur with a short-term fever, and after the temperature is normal, asthenia persists for a long time. The most characteristic symptoms of the western Nile fever caused by the "old" strains of the virus, in addition to those listed, are scleritis, conjunctivitis, pharyngitis, polyadenopathy, rash, hepatolyenal syndrome. Dyspeptic disorders are frequent (enteritis without pain syndrome). The defeat of the central nervous system in the form of meningitis and encephalitis is rare. In general, the course of the disease is benign.

Symptoms of West Nile fever caused by "new" strains of the virus differ significantly from those described above. Yu.Ya. Vengerov and A.E. Platonov (2000) on the basis of observations and serological studies proposed a clinical classification of the fever of the western Nile. Subclinical infection is diagnosed in screening studies of the population by the presence of antibodies of IgM class or the growth of titer of antibodies of IgG class by four or more times. The flu-like form has no clinical specificity. It is the least studied, because often, due to the short duration of the disorder of health, patients do not go to the doctor or their illnesses are assessed at the polyclinic level as influenza, ARVI.

Clinical classification of West Nile fever

The form	Degree of severity	Diagnostics	Exodus
Subclinical	-	Screening for the presence of antibodies of IgM class or an increase in the titer of IgG antibodies	-
Flu-like	Light	Epidemiological, serological	Recovery
Flu-like with neurotock-sycosis	Medium Heavy	Epidemiological, clinical. PCR. Serological	Recovery
Meningeal	Medium Heavy Heavy	Epidemiological, clinical liquorological. PCR serological	Recovery
Meningoencephalic	Heavy, very heavy	Epidemiological clinical. Liquorological. PCR, serological	Mortality to 50%

With influenza-like form with neurotoxicosis on the 3-5th day of the disease, there is a sharp deterioration of the condition, which is manifested by increased headache, the appearance of nausea, vomiting, muscle tremor, ataxia, dizziness and other symptoms of CNS damage. The fever in these cases is high, lasting 5-10 days. Specific clinical symptoms of West Nile fever-scleritis, conjunctivitis, diarrhea, rash-are observed in isolated cases. Symptoms of the central nervous system predominate: intense headache of diffuse nature, nausea, in half of patients - vomiting. Frequent symptoms - dizziness, adynamia, retardation, radicular pain, hyperesthesia of the skin. More than half of the patients are diagnosed with meningeal syndrome, in some cases - increased blood pressure. When studying the cerebrospinal fluid, in addition to increasing LD, there is no other pathology.

In patients with meningeal disease, meningeal symptoms of the western Nile fever accrue for 2-3 days; the most pronounced stiffness of the muscles of the occiput. In comparison with influenza-like form with neurotoxicosis, general cerebral symptoms are also noted, and transient focal symptoms are noted. Most characteristic: stupor, muscle tremor, anisoreflexia, nystagmus, pyramidal signs.

When carrying out a spinal puncture, the transparent or opalescent spinal fluid flows out under increased pressure. Cytosis varies widely - from 15 to 1000 cells in 1 μl (in most cases 200-300 cells per 1 μl) and is often mixed. In the study in the first 3-5 days of the disease in some patients, neutrophil cytosis (up to 90% of neutrophils). Mixed cytosis is often maintained until 2-3 weeks. Which, apparently, is due to the presence of necrosis of a significant part of the neurocyte. This explains the slower sanitation of the cerebrospinal fluid, which is often prolonged until the 3rd-4th week of illness. The amount of protein within 0.45-1.0 g / l, the glucose content - at the upper limits of the norm or increased, the sediment samples are weakly positive. The course of the disease is benign. Fever duration 12 days. Meningeal symptoms regress within 3-10 days. After the normalization of the temperature, weakness, fatigue increased.

The meningoencephalic form of the western Nile fever is most severe. The onset of the disease is stormy, hyperthermia and intoxication from the first days of illness. Meningeal symptoms of West Nile fever are mild or moderate. From the 3rd-4th day the general cerebral symptoms increase: confusion, excitement, delirium, sopor, in some cases passing into a coma. Often cramps, paresis of cranial nerves, nystagmus, less often - paresis of extremities, in the most severe cases, respiratory disorders dominate, central hemodynamic disorders. Mortality up to 50%. The recovered often retains paresis, muscle tremor, prolonged asthenia. Pleocytosis of the cerebrospinal fluid from 10 to 300 cells in 1 μl, the protein content reaches 0.6-2.0 g / l.

The picture of blood with a fever of the western Nile is characterized by features peculiar to severe viral infections: a tendency to leukocytosis, neutrophilia, lymphopenia, an increase in ESR. Despite the absence of clinical symptoms, in the urine - proteinuria. Cylinduria. Leukocyturia.

Mortality among hospitalized patients is about 4-5%, which allows attributing the fever of the western Nile to severe (dangerous) viral neuroinfections.