What is Adenovirus infection?
Adenovirus infection is an acute anthroponotic viral infection that affects the mucous membranes of the upper respiratory tract, eyes, intestines, lymphoid tissue and proceeds with moderately severe intoxication.
Human adenoviruses first isolated W. Rowe (1953) from the tonsils and adenoids of children, and then in patients with SARS and atypical pneumonia with conjunctivitis (Huebner R., Hilleman M., Trentin J. et al., 1954). In animal experiments, oncogenic activity of adenoviruses has been proven (Trentin J. et al., Huebner R. et al., 1962).
Causes of Adenovirus Infection
Pathogens are DNA-genomic viruses of the genus Mastadenovirus of the family Adenoviridae. Currently, about 100 serovars of viruses are known, more than 40 of them have been isolated from humans. Adenovirus serovars differ sharply in their epidemiological characteristics. Serovars 1, 2 and 5 cause damage to the respiratory tract and intestines in young children with prolonged persistence in the tonsils and adenoids, serovars 4, 7, 14 and 21 – SARS in adults. Serovar 3 causes the development of acute pharyngoconjunctival fever in older children and adults, several serovars cause epidemic keratoconjunctivitis. Outbreaks of disease are more often due to types 3, 4, 7, 14 and 21.
According to their ability to agglutinate erythrocytes, adenoviruses are divided into 4 subgroups (I-IV). Adenoviruses are stable in the environment, persist up to 2 weeks at room temperature, but die from exposure to ultraviolet rays and chlorine-containing drugs. Well tolerated by freezing. In water at 4 ° C, they retain vital activity for 2 years.
The reservoir and source of infection is a person, patient or carrier. The pathogen is excreted from the body with the secret of the upper respiratory tract until the 25th day of illness and more than 1.5 months – with feces.
The mechanism of infection is an aerosol (with droplets of saliva and mucus), and a fecal-oral (alimentary) route of infection is also possible. In some cases, the transmission of the pathogen is carried out through contaminated objects of the environment.
The natural susceptibility of people is high. The transferred disease leaves a type-specific immunity, repeated diseases are possible.
Major epidemiological signs. Adenovirus infection is widespread, accounting for 5-10% of all viral diseases. The incidence is recorded throughout the year with a rise in the cold season. Adenoviral diseases are observed both in the form of sporadic cases and in the form of epidemic outbreaks. Epidemic types of viruses (especially 14 and 21) cause large outbreaks of disease among adults and children. Adenoviral hemorrhagic conjunctivitis occurs more often when infected with virus 3, 4 and 7 types. The development of cases of conjunctivitis is associated with a postponed respiratory adenovirus infection, or is the result of infection by the virus through water in swimming pools or open water bodies. More often sick children and military personnel. Particularly high incidence in newly formed groups of children and adults (in the first 2-3 months); the disease proceeds as ARVI. In some cases, possible nosocomial infection during various medical procedures. The disease in newborns and young children proceeds according to the type of keratoconjunctivitis or lesions of the lower respiratory tract. Rare adenoviral lesions include meningoencephalitis and hemorrhagic cystitis, often detected in older children.
SARS, including influenza, make up a complex of associated infections, therefore the process of spreading these infections is a single balanced system. Currently, about 170 types of pathogens causing influenza-like diseases are known, and even during the epidemic period, the proportion of influenza accounts for no more than 25-27% of all SARS.
Pathogenesis during adenovirus infection
During aerosol infection, the pathogen enters the human body through the mucous membranes of the upper respiratory tract and spreads through the bronchi to their lower parts. The entrance gates of infection can be the mucous membranes of the eyes, as well as the intestines, where the virus enters when mucus is swallowed from the upper respiratory tract. The virus is localized in the epithelial cells of the respiratory tract and small intestine, where it multiplies. An inflammatory reaction develops in the lesions, accompanied by enlarged mucosal capillaries, hyperplasia of the submucosal tissue with infiltration of mononuclear leukocytes and sometimes hemorrhages in it, which is clinically manifested by angina, pharyngitis, conjunctivitis (often membranous), diarrhea. Sometimes keratoconjunctivitis develops with corneal clouding and visual impairment. Lymphogenous way pathogen penetrates into the regional lymph nodes, where there is hyperplasia of lymphoid tissue and accumulation of the virus during the incubation period of the disease. In the clinical picture, these mechanisms determine the development of peripheral lymphadenopathy and mesadenitis.
As a result of the suppression of the activity of macrophages and an increase in the permeability of tissues, viremia develops with the dissemination of the pathogen in various organs and systems. During this period, the virus enters the vascular endothelium cells, damaging them. At the same time often intoxication syndrome is observed. The fixation of the virus by macrophages in the liver and spleen is accompanied by the development of changes in these organs with an increase in their size (hepatolienal syndrome). Viremia and reproduction of the pathogen in epithelial cells and lymphoid tissue can be long.
Symptoms of Adenovirus Infection
The duration of the incubation period varies from 1 day to 2 weeks, often amounting to 5-8 days. The disease begins acutely with the development of mild or moderate symptoms of intoxication: chills or chills, a weak and intermittent headache, myalgia and arthralgia, lethargy, adynamia, loss of appetite. From the 2-3rd day of illness, the body temperature begins to rise, more often it remains subfebrile for 5-7 days, only sometimes reaching 38-39 ° C. In rare cases, epigastric pain and diarrhea are possible.
At the same time, symptoms of lesions of the upper respiratory tract develop. Unlike the flu, moderate nasal congestion appears early with abundant serous, and later, serous-purulent discharge. There may be sore throat and cough. After 2-3 days from the onset of the disease, patients begin to complain of pain in the eyes and excessive tearing.
On examination of patients, facial flushing, scleral injection, and sometimes papular skin rash can be noted. Conjunctivitis often develops with conjunctival hyperemia and mucous, but not purulent discharge. In children of the first years of life and occasionally in adult patients with a conjunctiva, a lumpy formation may appear, eyelid swelling is increasing. Possible damage to the cornea with the formation of infiltrates; when combined with catarrhal, purulent, or membranous conjunctivitis, the process is usually unilateral at first. Infiltrates on the cornea resolve slowly over a period of 1-2 months.
Conjunctivitis can be combined with symptoms of pharyngitis (pharyngoconjunctival fever).
The mucous membrane of the soft palate and the posterior pharyngeal wall is slightly inflamed, may be granular and edematous. The follicles of the posterior pharyngeal wall are hypertrophied. The tonsils are enlarged, loosened, sometimes covered with easily removable, friable, whitish patches of various shapes and sizes. There is an increase and pain on palpation of the submandibular, often cervical and even axillary lymph nodes.
If the inflammatory process of the respiratory tract takes a descending character, the development of laryngitis and bronchitis is possible. Laryngitis in patients with adenovirus infection is rarely observed. It is manifested by a sharp “barking” cough, increased sore throat, hoarseness. In cases of bronchitis, the cough becomes more persistent, in the lungs they listen to hard breathing and scattered dry rales in different departments.
The period of catarrhal phenomena can sometimes be complicated by the development of adenoviral pneumonia. It occurs after 3-5 days from the onset of the disease, in children under 2–3 years of age it can begin suddenly. At the same time, body temperature rises, fever takes the wrong character and lasts a long time (2-3 weeks). Cough becomes stronger, general weakness progresses, shortness of breath occurs. Lips take cyanotic hue. When walking, shortness of breath increases, perspiration appears on the forehead, lip cyanosis increases. According to radiological signs, pneumonia can be small-focal or confluent.
In young children, in severe cases of viral pneumonia, maculopapular rash, encephalitis, and foci of necrosis in the lungs, skin, and brain are possible.
Pathological changes in the cardiovascular system develop only with rare severe forms of the disease. Characterized by the muffled tones of the heart and a soft systolic murmur at its apex.
Lesions of various parts of the respiratory tract can be combined with disorders of the gastrointestinal tract. There are abdominal pains and intestinal dysfunction (diarrhea is especially characteristic of young children). Enlarged liver and spleen.
Adenovirus infection often affects children and middle-aged people. On average, the disease lasts from several days to 1 week, but with a long delay of the virus in the body, a relapsing course is possible, and the infection is delayed for 2-3 weeks.
According to the prevalence of certain symptoms and their combination, there are several forms of the disease:
- pharyngoconjunctivitis (pharyngoconjunctival fever);
- conjunctivitis and keratoconjunctivitis;
- pneumonia, etc.
Complications of adenovirus infection
The most typical are otitis and purulent sinusitis, obstruction of the Eustachian tube in children due to prolonged lymphoid tissue hypertrophy in the pharynx, laryngospasm (false croup), secondary bacterial pneumonia, and kidney damage. The prognosis of the disease is usually favorable.
Diagnosis of Adenovirus Infection
Depending on the clinical form of adenovirus infection, differential diagnostics are conducted with influenza, a group of acute respiratory viral infections, conjunctivitis and keratoconjunctivitis of various etiologies (including diphtheria), pneumonia, and tuberculosis.
Adenovirus infection is characterized by mild or moderate intoxication and polymorphism of clinical manifestations in the dynamics of the disease: symptoms of airway damage (pharyngitis, laryngitis, bronchitis), eyes (conjunctivitis, iritis), regional or advanced lymphadenopathy, sometimes exanthema, gastrointestinal disorders, hepatolienal syndrome .
Laboratory diagnosis of adenovirus infection
Hemogram in adenoviral infections has no significant changes, except for a slight increase in ESR. Virological studies, based on the isolation of the virus from nasopharyngeal swabs, detachable eyes in conjunctivitis (less often from feces), are complex and lengthy, they are not used in wide practice. Detection of serum antibodies is carried out using a group-specific CSC and type-specific rtga and PH. When setting these reactions with paired sera taken in the acute period of the disease and the recovery period, the increase in antibody titers is considered to be diagnostically significant at least 4 times. Also used ELISA with group antigen. For an indicative rapid diagnosis, you can use the REEF and the method of immune electron microscopy.
Treatment of Adenovirus Infection
When uncomplicated course of the disease is usually limited to carrying out local activities: prescribed eye drops (0.05% solution of deoxyribonuclease or 20-30% solution of sulfacyl sodium). In case of purulent or membranous conjunctivitis and keratoconjunctivitis (excluding cases with cornea ulcerations!), A 1% hydrocortisone or prednisone ointment is placed behind the eyelid. Recommended vitamins, antihistamines, symptomatic agents.
Severely flowing adenovirus infection requires increased detoxification therapy with intravenous administration of polyionic crystalloid and colloid solutions. Etiotropic drugs (broad-spectrum antibiotics) are prescribed for complications caused by secondary bacterial flora, as well as to elderly people suffering from chronic diseases of the respiratory system, and patients with manifestations of immunosuppression.
Prevention of Adenovirus Infection
In a number of countries, live adenovirus vaccine is used for prevention in adults organized groups. In Ukraine, immunization has not been developed. The widespread use of live vaccines limits the current opinion about the ability of adenoviruses to cause malignant cell transformations in humans. Recommended general sanitation and hygiene measures, chlorination of water in swimming pools. In the pre-epidemic period, it is recommended to limit communication to weakened children of toddlers who are at risk of infection, the introduction of a specific immunoglobulin and leukocyte interferon is indicated.