Acute respiratory viral infections (ARVI) occupy one of the first places among all infectious diseases in humans. These are the most common diseases in the world. Tens of millions of people suffer from acute respiratory viral infections every year.

Acute respiratory viral infections are a large group of diseases, usually occurring in an acute form, caused by viruses and transmitted by airborne droplets. The causative agent exists in two forms: the virion is an extracellular form and the virus is an intracellular form. Almost everyone suffers from acute respiratory viral infections several times a year, especially children. Children from birth to six months of life get sick less often, since they have little contact with the outside world and have passive immunity received from the mother transplacentally. It should be remembered that innate immunity may be relaxed or completely absent, which means that the child may get sick. The highest morbidity occurs in children in the second half of the year and the first three years of life, which is associated with their attendance at kindergartens, and, consequently, an increase in the number of contacts. All respiratory diseases have common clinical manifestations: fever, the presence of symptoms of intoxication of varying severity and symptoms of respiratory tract damage, the clinical manifestations of which depend on the localization of the inflammatory process.

Acute respiratory viral infections must be differentiated from acute respiratory diseases (ARI), since the pathogens of the latter can be not only viruses, but also bacteria.

Therefore, etiotropic is not antiviral, but antibacterial treatment.

The most common causes of acute respiratory viral infections are: influenza, parainfluenza, respiratory syncytial, adenovirus, coronavirus and rhinovirus infections. In the etiological structure of acute respiratory viral infections, influenza viruses, parainfluenza and adenovirus infection prevail.

As mentioned above, all these diseases are characterized by a lesion of the respiratory tract with different localization of the process. So, with influenza, the mucous membrane of the upper respiratory tract is affected, with parainfluenza – mainly the mucous membrane of the larynx (for serotypes 1 and 2) and the mucous membrane of the lower respiratory tract (for serotype 3). Adenovirus infection is characterized by damage to the mucous membrane of the respiratory tract, mainly the pharynx, as well as the mucous membrane of the eyes and gastrointestinal tract. In respiratory syncytial infection, the mucous membrane of the lower respiratory tract is involved in the pathological process, in coronavirus infection, the pathogen affects the upper respiratory tract, and in young children – the bronchi, lungs, and with rhinovirus infection, damage to the nasal mucosa is typical. Diseases caused by respiratory viruses are classified into a large number of syndromes: colds, pharyngitis, croup (laryngotracheobronchitis), tracheitis, bronchiolitis and pneumonia. Isolation of these groups of diseases is advisable from both an epidemiological and a clinical point of view. However, most of the respiratory viruses are capable of causing not one, but several clinical syndromes, and very often one patient may simultaneously show signs of several of them.

Almost all acute respiratory viral diseases are anthroponotic diseases, with the exception of coronavirus and adenovirus infections, which can also affect animals. The main source is a sick person, less often a convalescent (recovering person). With adenoviral and respiratory syncytial infection, the source of the disease can be a virus carrier (there are no clinical manifestations of the disease, a diagnosis can be made only with the help of specific laboratory research methods (virological and serological methods). An aerogenic mechanism of infection, airborne transmission of infection, but with adenoviral infection is sometimes observed fecal-oral mechanism of infection. Quite often the source of infection of children are adults, especially those who carry the disease “on their feet.” At the same time, adults often regard their condition as a “mild cold.” Almost all so-called colds are viral in nature , and such patients pose a great danger to children, especially young children.

A child of any age can get sick with acute respiratory viral infections, but each disease has its own age specificity. For example, parainfluenza occurs more often in preschool children than acute respiratory diseases of other etiology. It should be noted that parainfluenza affects children in the first months of life and even newborns, while transplacental transmission of IgG antibodies provides a relatively low susceptibility to influenza in children under six months of age. Children aged six months to five years are most susceptible to adenovirus infection. A significant part of newborns and children in the first half of life have natural (passive) immunity. Respiratory syncytial infection mainly affects young children and even newborns. With rhinovirus and coronavirus infections, susceptibility is observed equally in all age groups, but preschool children are more likely to get sick.

In all acute respiratory diseases there is an incubation (latent) period, but with varying duration: with influenza it is the shortest (from several hours to 2-3 days) and the longest with adenovirus infection (from 5-8 to 13 days). In other infections, this period is on average 2-6 days (parainfluenza – 3-4 days, respiratory syncytial infection 3-6 days, rhinovirus infection 2-3 days, coronavirus infection 2-3 days).

With all these diseases, the clinical picture is characterized by the appearance of intoxication syndrome and catarrhal syndrome of varying severity. Intoxication is most intense with influenza and least of all with rhinovirus infection, in which the general condition of the patient practically does not suffer. Despite its name – “acute respiratory viral infections” – an acute onset is characteristic only for influenza, adenovirus infection and may be with parainfluenza. For other diseases, a gradual onset is more typical. Hyperthermia (increased body temperature) is also not always noted. So, with the flu, already on the first day, the temperature becomes febrile, and in some cases even hectic (38-40 ° C); with adenovirus infection and respiratory syncytial infection, the temperature can rise to 38-39 ° C, but by 2-4 days of illness. In some cases, fever can be two-wave (occurs with adenovirus infection and less often with influenza). In the typical course of other acute respiratory diseases, the body temperature is usually normal or subfebrile (if there are no complications).

Each acute respiratory viral infection is characterized by the presence of catarrhal syndrome in varying degrees of severity. This syndrome is manifested by redness, hyperemia, swelling of the nasal mucosa, posterior pharyngeal wall, soft palate, tonsils, as well as fine granularity of the posterior pharyngeal wall due to an increase in follicles. Typical is the defeat of the cardiovascular (tachycardia, muffling of heart sounds, systolic murmur is heard at the apex of the heart), respiratory (the presence of hard breathing and wheezing during auscultation of the lungs, in some cases the appearance of signs of respiratory failure) systems. Less commonly, the digestive (intestinal dysfunction, abdominal pain, liver enlargement), as well as the central nervous system (in the form of seizures, meningeal symptoms, encephalitis phenomena) are involved in the pathological process. In the development of acute respiratory viral infections, an important role belongs to mixed pathology (mixed pathology), due to complex viral-bacterial associations (interactions) with the development of secondary processes: catarrh of the upper respiratory tract, tonsillitis, bronchitis, pneumonia. In essence, they enhance the pathological effect of each other and often cause a severe course of the disease and even its death. Immunity after acute respiratory viral infections is usually short-lived, type-specific.

All acute respiratory viral infections are characterized by great difficulty in diagnosis. The clinical forms of diseases caused by these viruses rarely have sufficiently specific signs, on the basis of which an etiological diagnosis can be established only from clinical data, although when taking into account the epidemiological conditions, it is highly probable which group of viruses caused the disease. To make a final diagnosis, it is not enough just clinical manifestations and taking into account the epidemiological conditions. It is necessary to use specific research methods. These include methods of early diagnosis – the study of smears from the mucous membrane of the oropharynx and nose by the method of fluorescent antibodies or using enzyme-linked immunosorbent assay (ELISA) to detect viral antigens. Serological methods are used: the complement fixation reaction (RSC), the hemagglutination inhibition reaction (RTGA) and the neutralization reaction (RN), which are retrospective, since in order to make a diagnosis, it is necessary to identify antibodies to the influenza virus in paired sera taken in the first days of the disease, and then after 5-7 days.
The diagnostic is the increase in the antibody titer four times or more.

They also use virological methods. Influenza viruses can be cultured (grown) in chicken embryos and mammalian cell cultures.

Also, all these diseases have similar points of treatment and prevention.

The principles of treating a patient with acute respiratory viral infection can be formulated in the following main provisions.

1. A sick child should be on bed rest, especially during the temperature rise, as isolated as possible. It is recommended to drink plentifully in the form of warm tea, cranberry or lingonberry juice, alkaline mineral waters. 

2. Etiotropic therapy. Treatment aimed at suppressing reproduction and eliminating the action of toxins and other factors of aggression of the pathogen (antiviral drugs, immunoglobulins). 

3. Pathogenetic therapy (treatment aimed at maintaining the normal function of the most important life support systems of the child). Interferon (human leukocyte), influenza, glucocorticosteroid drugs, detoxification drugs (oral rehydration or infusion therapy), desensitizing agents, protease inhibitors, vasoactive drugs and other drugs are prescribed. 

4. Symptomatic therapy: it includes antipyretics (paracetomol, ibuprofen), mucolytic (acetylcysteine), expectorants (lazolvan, ambrohexal, bromhexine), vasoconstrictors (nasivin, naphthyzine) and other drugs. 

5. Local therapy – medicinal inhalations, gargling with antiseptic solutions. 

Children with severe and complicated forms of the disease are subject to compulsory hospitalization. Frequent acute respiratory diseases lead to a weakening of the defenses of the child’s body, contribute to the formation of chronic foci of infection, cause allergization of the body and delay the physical and psychomotor development of children. In many cases, frequent acute respiratory viral infections are pathogenetically associated with asthmatic bronchitis, bronchial asthma, chronic pyelonephritis, polyarthritis, chronic diseases of the nasopharynx and many other diseases.

Prevention consists of early detection and isolation of patients; increasing the nonspecific resistance of the body (doing physical education and sports, hardening the body, rational nutrition, prescribing vitamins according to indications). During outbreaks of acute respiratory viral infections, visits to clinics, events, and sick relatives should be limited. Persons who have communicated with patients are prescribed antiviral drugs (for example, oxolinic ointment). The room where the patient is located must be regularly ventilated, wet cleaning with 0.5% chloramine solution. In the outbreak, current and final disinfection is carried out, in particular, boiling of dishes, linen, towels, and handkerchiefs of patients. Apply live or killed vaccines (for influenza).

The prognosis is favorable, but deaths are possible in severe and complicated course of the disease, especially with influenza.