Smallpox is an infectious human disease related to particularly dangerous infections caused by the Orthopoxvirus variola virus, characterized by fever, intoxication and specific rashes on the skin and mucous membranes. The spread of smallpox occurs by aerosol, while the pathogen is so stable in the air that it can cause infection of people who are not only in the same room with the patient, but also in neighboring rooms. In the mid-70s of the twentieth century, the complete elimination of smallpox in developed countries led to the abolition of preventive vaccination against this disease.
The Orthopoxvirus variola virus belongs to the group of animal and human smallpox viruses, is stable in the environment, easily tolerates temperature drop and drying, can remain viable when frozen for several years. At room temperature, it persists in smallpox crusts for up to a year, in sputum and mucus for up to three months. When heated to 100 ° C, the virus in dried form dies only after 5-10 minutes.
The reservoir and source of smallpox is a sick person. The virus is isolated throughout the entire period of rashes, patients are especially contagious in the first 8-10 days. Asymptomatic and convalescent carrier is not noted, chronization is not characteristic. The predominant localization of the pathogen in the human body is the mucous membranes of the oral cavity, nose, pharynx, upper respiratory tract, excretion occurs with coughing, sneezing, during breathing. The skin can also serve as a place of release of the pathogen.
Smallpox is transmitted by aerosol mechanism mainly by airborne droplets and airborne dust routes. The aerosol with the pathogen is able to move with the air current for a considerable distance, affecting people who are located in the same room with the patient, and penetrating into neighboring rooms. Smallpox tends to spread in multi-storey apartment buildings, medical institutions, crowded collectives.
A person’s natural susceptibility is high. Non-immunized persons are infected in the vast majority of cases, the percentage of immune persons is no more than 12 out of 100 unvaccinated (on average 5-7%). After the transfer of the disease, a stable long-term (more than 10 years) immunity is formed.
The incubation period of smallpox is usually 9-14 days, it can increase up to 22 days. There are periods of the disease: prodromal (or the period of precursors), rashes, suppuration and convalescence. The prodromal period lasts from two to four days, there is fever, symptoms of intoxication (headache, chills, weakness, muscle pain, lower back). At the same time, a rash resembling an exanthema with measles or scarlet fever may be found on the hips and chest.
By the end of the prodromal period, the fever usually subsides. On 4-5 days, a smallpox rash appears (a period of rash), initially representing small roseoles, progressing into papules, and after 2-3 days – into vesicles. Vesicles have the form of multicameral small bubbles surrounded by hyperemic skin and having a small umbilical depression in the center. The rash is localized on the face, trunk, limbs, not excluding the palms and soles, unlike chickenpox, the elements of the rash in one zone are monomorphic. With the progression of the rash, fever and intoxication increase again.
By the end of the first week of the disease, at the beginning of the second, a period of suppuration begins: the temperature rises sharply, the condition worsens, the rash elements are inflamed. Smallpox lose their multi-chamber, merging into a single purulent pustule, become painful. A week later, the pustules are opened, forming black necrotic crusts. The skin begins to itch violently. On 20-30 days, the period of reconvalescence begins. The patient’s body temperature gradually normalizes from 4-5 weeks of the disease, the pockmarks heal, leaving behind pronounced peeling, and later – scars, sometimes very deep.
There are severe clinical forms of smallpox: papular hemorrhagic (smallpox), drain and smallpox purpura. The moderate course has scattered smallpox, light – smallpox without rash and temperature: varioloid. In this form, smallpox usually occurs in vaccinated individuals. Rare rashes that do not leave scars are characteristic, there are no intoxication symptoms.
Most often, smallpox is complicated by infectious and toxic shock. There are complications of an inflammatory nature on the part of the nervous system: myelitis, encephalitis, neuritis. There is a possibility of secondary infection and the development of purulent complications: abscesses, phlegmon, lymphadenitis, pneumonia and pleurisy, otitis media, osteomyelitis. Sepsis may develop. After the transfer of smallpox, there may be consequences in the form of blindness or deafness.
Diagnosis and treatment
Diagnosis of smallpox is carried out by viroscopic examination using an electron microscope, as well as virological and serological methods: microprecipitation in agar, ELISA. The study is subject to the separation of smallpox pustules and crusts. From 5-8 days of the disease, it is possible to determine specific antibodies using NR, IFT, HI, ELISA.
Treatment of smallpox consists in the appointment of antiviral drugs (metisazone), the introduction of immunoglobulins. The skin affected by smallpox rash is treated with antiseptic agents. Additionally (due to the purulent nature of the infection), antibiotic therapy is prescribed: antibiotics of the groups of semi-synthetic penicillins, macrolides and cephalosporins are used. Symptomatic therapy consists in active detoxification by intravenous infusion of glucose solutions, water-salt solutions. Sometimes glucocorticoids are included in therapy.
Prognosis and prevention
The prognosis depends on the severity of the course and the condition of the patient’s body. Vaccinated persons, as a rule, carry smallpox in a mild form. Severe smallpox with a hemorrhagic component can end in death.
Currently, specific prevention of smallpox is carried out in order to prevent its import from epidemiologically dangerous regions. The elimination of smallpox in developed countries has been achieved through mass vaccination and revaccination of the population for several generations, currently planned universal vaccination is impractical. In case of detection of a patient with smallpox, they isolate him, as well as carry out quarantine measures against all who have had contact with the patient. Thorough disinfection is carried out in the focus of infection, contact persons are vaccinated within the first three days from the moment of contact.