Swine flu is a highly contagious disease of animals and humans caused by the influenza virus serotype A (H1N1) and prone to pandemic spread. In its course, disease resembles the usual seasonal flu (fever, weakness, body aches, sore throat, rhinorrhea), but differs from it in some features (the development of dyspeptic syndrome). Diagnosis is based on clinical signs; PCR, virological and serological studies are carried out to determine the type of virus. Treatment involves the appointment of antiviral (interferons, umifenovir, oseltamivir, kagocel) and symptomatic (antipyretic, antihistamine, etc.) drugs.
Swine flu is an acute respiratory viral infection transmitted from pigs to humans and within the human population. The causative agent of swine flu was discovered back in 1930, but for the next half century it circulated in a limited area (in North America and Mexico) only among domestic animals, mainly pigs. Isolated cases of infection of people (mainly veterinarians and pig farm workers) with swine flu have been recorded since the early 1990s. In 2009, the swine flu pandemic, known as “California/2009”, shook the world, covering 74 countries, including European states, Russia, China, Japan and many others. Then, according to WHO, more than 500 thousand people fell ill with swine virus. The greatest susceptibility to the virus was demonstrated by persons aged 5 to 24 years. Due to the ability of the virus to be easily transmitted from person to person, as well as the tendency to pandemic spread, disease was assigned the highest hazard class 6.
Several types and serotypes of influenza virus are circulating in the pig population: human seasonal influenza viruses, avian influenza viruses, H1N1, H1N2, H3N2, H3N1. It is assumed that serotype A (H1N1), which causes swine flu in humans, was the result of recombination (reassortment, mixing) of various subtypes of the influenza virus. It is the hybrid virus A(H1N1) that has acquired the ability to overcome the interspecific barrier, cause disease among humans and be transmitted from person to person. Like other human influenza viruses, A(H1N1) contains RNA; the virions of the pathogen have an oval shape. The virus envelope contains specific proteins – hemagglutinin and neuraminidase, which facilitate the attachment of the virus to the cell and its intracellular penetration. Virus is not stable in the external environment: it is quickly inactivated when heated, exposed to traditional disinfectants and ultraviolet light, but it can tolerate low temperatures for a long time.
The sources of the virus can be infected or sick pigs and humans. The main way of spreading swine flu in the human population is airborne (with mucus particles released during coughing, sneezing), less often – contact and household (by entering the patient’s secretions from the hands and household items on the mucous membranes of the mouth, nose, eyes). Cases of alimentary infection when eating meat of infected animals are unknown. Despite the high and universal susceptibility of people to the swine flu virus, children younger than 5 years and the elderly, pregnant women, patients with concomitant diseases (CKD, diabetes mellitus, liver and kidney diseases, cardiovascular system, HIV infection) are at risk of developing severe clinical forms of infection.
The pathogenesis is generally similar to the pathological changes occurring in the body during normal seasonal flu. Replication and reproduction of the virus occurs in the epithelium of the respiratory tract and is accompanied by superficial damage to the cells of the tracheobronchial tree, their degeneration, necrosis and desquamation. During the period of viremia lasting 10-14 days, toxic and toxic-allergic reactions from the internal organs prevail.
The incubation period is from 1 to 4-7 days. An infected person becomes contagious already at the end of the incubation period and continues to actively secrete viruses for another 1-2 weeks, even against the background of ongoing therapy. The severity of clinical manifestations varies from asymptomatic to severe with a fatal outcome. In typical cases, the symptoms of swine flu resemble those of acute respiratory viral infections and seasonal flu. The disease begins with an increase in temperature to 39-40 ° C, lethargy, weakness, muscle aches, arthralgia, lack of appetite. With severe intoxication, intense headaches occur, mainly in the frontal region, pain in the eyeballs, which increases with eye movement, photophobia. Catarrhal syndrome develops, accompanied by tickling and sore throat, runny nose, dry cough. A characteristic distinguishing feature of swine flu, observed in 30-45% of patients, is the occurrence of dyspeptic syndrome (abdominal pain, constant nausea, repeated vomiting, diarrhea).
The most common complication of swine flu is primary (viral) or secondary (bacterial, more often pneumococcal) pneumonia. Primary pneumonia usually occurs as early as 2-3 days of the disease and can lead to the development of respiratory distress syndrome and death. It is possible to develop infectious and allergic myocarditis, pericarditis, hemorrhagic syndrome, meningoencephalitis, cardiovascular and respiratory insufficiency. Swine flu exacerbates and aggravates the course of concomitant somatic diseases, which affects the overall prospects of recovery.
Diagnosis and treatment
Making a preliminary diagnosis is difficult due to the absence of purely pathognomonic signs, similarity of symptoms of swine and seasonal flu. Therefore, the final diagnosis is impossible without laboratory identification of the viral pathogen. In order to determine the RNA of the influenza A (H1N1) virus, a smear from the nasopharynx is examined by PCR. Virological diagnostics involves the cultivation of swine flu virus in chicken embryos or on cell culture. To determine IgM and IgG in the blood serum, serological studies are performed – IFT, HI, ELISA. An increase in the titer of specific antibodies by more than 4 times indicates in favor of infection with the swine flu virus.
Treatment of swine flu consists of etiotropic and symptomatic therapy. Among antiviral drugs, interferons (alpha interferon, alpha-2b interferon), oseltamivir, zanamivir, umifenovir, kagocel are recommended. Symptomatic therapy includes taking antipyretic, antihistamine, vasoconstrictor drugs, infusion of electrolyte solutions. In secondary bacterial pneumonia, antibacterial agents (penicillins, cephalosporins, macrolides) are prescribed.
Prognosis and prevention
The prognosis for swine flu is significantly more favorable than for avian flu. Most people suffer from swine flu in mild form and recover completely. Severe forms of infection develop in 5% of patients. Deaths in swine flu are recorded in less than 4% of cases. Nonspecific prevention of swine flu is similar to other acute respiratory infections: exclusion of contacts with persons with signs of colds, frequent washing of hands with soap, hardening of the body, ventilation and disinfection of premises during the season of the rise of viral infections. For specific prevention of swine flu, the vaccine Grippol, etc. is recommended.