Symptoms of influenza in children
Influenza is an acute viral illness, unpleasant and contagious, often epidemic. It is characterized by a pronounced general infectious syndrome and respiratory tract infection.
Influenza pathogens are RNA viruses belonging to the family of orthomixoviruses( Orthomyxoviridae) and comprising three distinct types: A, B and C.
Influenza viruses are pleomorphic quasispherical particles with an external diameter of 100-110 nm and an inner core of 70 nm.
The surface of viral particles is covered with two types of spines( protrusions) up to 10 nm long, which determine hemagglutination or neuraminidase activity. Under the spines is a double lipid layer covering the protein shell, the latter in turn surrounds the nucleoprotein and forms the inside of the viral envelope, inside which lie a spiral ribonucleoprotein with a diameter of 9 nm. Nucleic acid is not a single molecule, it is divided into 8 components( fragments).The OMM of these fragments of RNA is 2-4 × 106 per virion. Separation of the genome into fragments causes such biological phenomena as high frequency of recombinations, multiple reactivation, the ability to synthesize haemagglutinins and neuraminidase after chemical inactivation of infectious properties of the virus.
Ribonucleoprotein contains not only the genome of the virus, but also the K-dependent RNA polymerase associated with the virion PH.Influenza viruses possess receptor-binding, enzyme( receptor-destroying), toxic, infectious and antigenic activity. The receptor-binding activity is manifested in the ability of the virus to be adsorbed on special receptors, is associated with haemagglutinins contained in thorns. The adsorption of the virus with the help of hemagglutinin-containing spines on erythrocytes leads to their agglutination. Enzyme or receptor-destroying activity is associated with a proteinase neuraminidase enzyme contained in thorns, which ensure the penetration of the virus into the host cell.
The toxic function of influenza viruses is associated with the secretion of toxins, which is manifested in the clinic due to the presence of leukopenia with neutropenia, bradycardia, respiratory tract epithelial necrosis, the presence of type-specific antibodies that neutralize only the corresponding toxins.
All types of the virus are characterized by genetic instability, constant and progressive variability of their antigenic structure, which explains the appearance of qualitatively new species, to which the population does not have immunity.
All types of influenza virus - obligate intracellular parasites, multiply in the cytoplasm, sometimes in the nucleus.
Influenza viruses are relatively resistant to temperature factors: at 4 ° C they persist for a week, at 0 ° C - much longer. Infectiousness is destroyed by heating at 50 ° C for several minutes, at 60 ° C - instantaneously. Formaldehyde, phenol, ether have a denaturing effect. They are bent under the influence of direct sunlight, ultrasound.
Infectious viral particles induce the formation of viral neutralizing and other antibodies.
Virion contains two subtypespecific antigens: hemagglutinin( H-Ar) and neuraminidase( N-Ar).H-Ar is the main specific antigen of the membrane and the associated antigenic differences between the strains of the virus. Antibodies to H-Ag neutralize the virus and have a protective effect.
N-Ar - differs from H-Ar and has an independent gene( fragment of RNA).Antibodies to N-Ar do not neutralize the virus, but change the course of the infectious process, inhibiting the process of releasing the virus from the cell.
A distinctive feature of the influenza A virus is the variability of the antigenic properties of surface proteins( glycoproteins), hemagglutinin( H-Ar) and neuraminidase( N-Ar).
There are 13 subtypes of N-Ar and 10 N-Ar subtypes in total. There are 4 subtypes of H-Ar( NO, HI, H2, NS) and 2 N-Ar subtypes( No. 1 and No. 2).The changes in H-Ar and N-Ar are independent of each other. The greatest variability is characteristic of H-Ar. It is possible to change both one Ar( antigenic drift) and two Ar( antigenic shift).The change of one antigen occurs every 2-3 years, two Ag is much less common.
The type B influenza virus has its antigen different from the type A and C virus antigen. Virus B is characterized by less polymorphism.
Virus C has not yet found antigenic variants, it does not cause pandemics and epidemics, it causes sporadic diseases, mainly in children.
The flu is found everywhere, characterized by a tendency to epidemic and pandemic spread.
The specific gravity of influenza in the ORI structure is from 25 to 60%.
Influenza is anthroponous infection. The source of infection is a sick person who is dangerous to others from the first hours of the disease and up to the 3-5th day of illness. A great danger for others is represented by patients with erased, subclinical forms.
In 15-20% of convalescents the release of the influenza virus can continue for 22-30 days.
The route of transmission of infection is airborne. The patient isolates viruses in large numbers during sneezing, coughing, and talking. In the form of aerosols in a suspended state, viruses can remain for several minutes.
Susceptibility to influenza is universal. Diseases are observed more often in winter and spring. Influenza A of the type occurs in the form of epidemics, pandemics that begin suddenly and rapidly spreading. The influenza C virus causes only sporadic diseases, the influenza B virus - local outbreaks, covering individual territories.
Increased detection rates of type C influenza often precede or accompany epidemic increases in influenza types A and B.
Patterns of the emidemic process in influenza in recent years:
• reduced frequency of intense influenza pandemics with increased activity of other respiratory viruses;
• one-stage circulation of influenza viruses of different serotypes: A( H32), A( Nm) and B;
• simultaneous circulation of different strains of influenza viruses of the same serotype;
• the most frequent connection to epidemic events of strains of the influenza B virus;
• epidemics are characterized by a slow spread and last 1-1.5 months;
• mostly children are ill.
The entrance gates of the infection are the upper respiratory tract.
Influenza viruses have pronounced tropism to the epithelium of the respiratory tract, especially to the cylindrical epithelium of the inferior nasal concha and trachea. Penetrating into them, the virus begins to be intensively reproduced, causing dystrophy, necrosis, and slimming of the epithelium. Damaged mucous membrane becomes permeable to viruses, involving the pathological process of the underlying tissues, vessels. The intensity and prevalence of pathological processes are determined by the virulence of the viruses and the susceptibility of infected people.
Pathogenic influenza viruses have on the nervous and cardiovascular systems.
Damage of endothelium of the terminal vascular bed by viruses leads to a sharp increase in capillary permeability, perivascular leukemia and tissue trophism disorder, hemocirculation disorder and blood rheology.
Disturbances of microcirculation are accompanied by hemodynamic disorders in various organs and systems. For example, circulatory disorders in the lungs lead to segmental or widespread hemorrhagic edema, in the nervous system to encephalopathy.
Then the virus with a blood stream gets to various organs. In particular, the intracerebral localization of the virus is proved, where it multiplies in the endothelium of the brain.
The general toxicity of the influenza virus causes suppression of immunity, including phagocytic activity of leukocytes, a decrease in the complementary function of blood serum, properdin, impaired immunoglobulin production. This contributes to the activation of endogenous and attachment of exogenous infections, the formation of severe bacterial complications.
Typical changes are dystrophic and proliferative changes in the epithelium of the upper respiratory tract, bronchi, bronchioles, diapedesis hemorrhages in the lung tissue, desquamative pneumonia on the background of plethora and pulmonary edema. Small hemorrhages in the pleura, under the epicardium and in other organs are revealed.
Expressed microcirculatory disorders are found in all organs in the form of congestion.
Histological examination of the mucous membrane of the nasal cavity reveals lymphocytic infiltrates, alterative changes in the integumentary epithelium, its rejection, in the trachea, bronchi - degeneration and desquamation of the epithelium, swelling of the basal membrane with an increase in its volume.
I. In clinical forms:
1. Typical: catarrhal, subtoxic, toxic.
2. Atypical: erased, fulminant( hypertoxic).
II.According to the leading clinical syndrome:
1. Stenosing laryngitis.
2. Bronchoobstruction.
3. Primary early lung lesions, segmental lung lesions.
4. Cerebral.
5. Abdominal.
6. Hemorrhagic.
7. Syndrome of sudden death.
III.By severity of the process:
1. Light.
2. Medium-heavy.
3. Heavy.
IV.In the course of the disease: acute.
V. By the nature of complications: encephalitis, meningitis, myocarditis, pneumonia, etc.
VI.Mixt infection.
The incubation period varies from a few hours to 2 days with influenza A and up to 3-4 days - with influenza B.
The disease begins acutely. In the first two days the picture of infectious toxicosis develops. The temperature rises rapidly to high figures with chills. The child complains of dizziness, headache, often in the forehead, superciliary arches, eyeballs, muscle and joint pain, abdominal pain. Appetite disappears, sleep is disturbed, nausea and vomiting appear. Often there are delusions, hallucinations, inhibition, in patients with severe forms - a violation of consciousness, clonicotonic convulsions, meningeal symptoms.
As a result of increased vascular permeability and hemodynamic disorders, nasal bleeding, hemorrhagic rash on the skin and mucous membranes, increased bleeding from the injection sites are possible.
There are violations of the autonomic nervous system: a sharp pallor of the skin, sometimes bright red cheeks, ak-rotsianoz. A pronounced vascular dystonia is revealed: the lability of the vascular pattern and the filling of the pulse, the tendency to lower blood pressure. Sweating is increased, dermographism is red.
Catarrhal syndrome in the first day is poorly expressed. Nasal congestion, shortness of nasal breathing. Palatine tonsils, arches slightly or moderately hyperemic, slightly swollen, in the soft palate - shallow enanthema or pinpoint hemorrhages. There may be herpetic eruptions around the nasal apertures or on the lips. The scleras are injected. Cough is dry painful.
The liver and spleen are not enlarged. Short-term stool disorders are possible.
The course of uncomplicated influenza is short( 5-7 days), the temperature persists for no more than 4-5 days.
Changes in the respiratory system in patients with influenza. In patients with influenza, respiratory damage is caused by two factors:
1. Epitheliotropic and capillarotoxic effect of the influenza virus on the mucous membranes of the respiratory system.
2. Attachment of exogenous or activation of endogenous bacterial infection as a result of development of immunodeficiency state. The following forms of respiratory damage are possible:
• upper respiratory catarrh, rhinopharyngitis;
• laryngitis, laryngotracheitis with croup syndrome;
• bronchitis with bronchial obstruction syndrome;
• Segmental edema of the lungs as a result of circulatory disorders within a single segment or lobe;
• primary interstitial pneumonia;
• with hypertoxic form - hemorrhagic pulmonary edema, hemorrhagic pneumonia;
• focal pneumonia of viral-bacterial origin.
Changes in the cardiovascular system in a patient with influenza can be of three kinds:
1. At the height of a toxicosis, functional disorders occur, expressed by muffled heart tones, tachycardia, impurity of the 1st tone. On the ECG - sharp high teeth P, reduced and dilated, often deformed teeth T.
In the period of convalescence, the detected disorders quickly disappear.
2. At the beginning of the period of convalescence, myocardial dystrophy is possible, characterized by sluggishness and lack of mobility of children, pallor of the skin, pulse lability, muffled heart sounds, systolic murmur. On the ECG - the reduction of all the teeth( especially P and T), the shift of the interval S-T, the increase in the interval Q-T, a violation in the conductor system. The revealed changes very slowly undergo reverse development.
3. Less often myocarditis develops, characterized by deafness of heart tones, extension of the borders of the heart, lowering of blood pressure. Myocarditis can be diffuse and focal, have a favorable outcome.
The clinical clinical symptoms of the flu .For the flu, which occurs in a typical form, is characterized by:
• acute, rapid onset of the disease;
• fever with chill in the first day to the maximum digits( 39-40 ° C), fever persists for 3 to 4 days;
• signs of intoxication that are rapidly growing during the first hours of the disease, persisting for 2-4 days;
• development of catarrhal syndrome in 24 hours, mandatory involvement in the trachea process.
Features of influenza in newborns and young children. The disease often has a gradual onset with a rise in body temperature to subfebrile, rarely - febrile digits. Symptoms of intoxication are moderately expressed. The child is disturbed by the expressed stuffiness of a nose, tussis. Croup syndrome in children of the first year of life is very rare.
The severity of the disease is due to the rapid attachment of bacterial infection( exogenous or endogenous) and the development of purulent complications( otitis media, pneumonia, urinary tract infection, etc.).
Specific prevention of influenza is carried out by inactivated and live vaccines, which are prepared from virus strains recommended annually by WHO.
Inactivated liquid influenza trivalent polymer-subunit vaccine "Grippol" is produced.
Product: ampoules of 0.5 ml( 1 dose), 10 ampoules per package. Store in a dry dark place and transport at 4-8 ° C, shelf life - 1 year 6 months. Applicable to persons aged 18 to 60 years. Widely used in Russia is the registered influenza inactivated split vaccine "Vaksigripp" of the firm "Pasteur Merier Connaught"( France), "Influvac"( Germany).
For vaccination of children "Vaksgrippp" is packaged in 1 infant dose( 0.25 ml) in an ampoule. Store and transport at a temperature of 2-8 ° C.Not subject to freezing. Shelf life - 1 year 6 months.
"Vaxigripp" is administered subcutaneously or intramuscularly to children from 6 months of age;children under 10 years of age with a period of 1 month in a dose of 0.25 ml, older than 10 years and adults - once 0.5 ml.
The inactivated vaccine "Fluariks" of the firm "SmithKleinBichem"( Belgium) is used for children and adults, either subcutaneously or intramuscularly. Children over 6 years and adults are injected with 0.5 ml once, children 1-6 years - 0.25 ml twice with an interval of 4-6 weeks.
Vaccines "Grippol", "Vaksgripp", "Fluarix" sometimes give short-term weak reactions in the first 48-72 hours after administration.
"Influvac vaccine" is administered intramuscularly or deep subcutaneously. The dose for children from 6 months to 3 years is 0.25 ml once. The dose for children from 3 to 14 years is 0.5 ml once.
Contraindications for all vaccines - allergy to egg hen proteins, acute infectious and non-infectious diseases, exacerbation of chronic diseases, progredient diseases of the nervous system, systemic connective tissue diseases, autoimmune diseases, blood diseases, bronchial asthma.