Can the pox virus family that damages the skin be contagious?

Poxvirus is the largest and most complicated virus among all viruses, and contains the largest DNA molecule. The virus particle contains a brick-like DNA core surrounded by several thin films. Viruses replicate and assemble in cytoplasm, which is different from other DNA viruses in vertebrates. Poxvirus can infect people and many kinds of animals, causing a variety of skin damage as purulent diseases. Human infection can lead to systemic or local acne rash. According to the differences in antigenicity and morphology, the undergraduate course is divided into two subfamilies: vertebrate poxvirus and insect poxvirus, some of which are unknown. Closely related to human beings are smallpox virus, vaccinia virus, monkeypox virus and infectious molluscum virus of unknown genus.

All members of the undergraduate course have the same nucleoprotein antigen, and members of the same genus have extensive cross neutralization reactions with each other, but members of different genera do not. Gene recombination only exists within the genus, and non-gene resurrection can occur within and between genera.

There are two kinds of vertebrate poxviruses: ① Vaccinia virus is the representative, including all members except parapoxvirus; ② It is represented by aphthous virus (contact pustular dermatitis virus), including all members of the genus Parapoxvirus.

The poxvirus represented by vaccinia virus is brick-shaped, with the size of (300 ~ 450) nm× (170 ~ 260) nm. There is a dumbbell-shaped core in the center of the virus particle, which contains the virus DNA bound to protein. The outer layer of virus particles consists of two membranes and cylindrical subunits. There are 1 lateral bodies on both sides of the core. The core and the lateral body are wrapped by an envelope, which is a double-layer membrane composed of phospholipids, cholesterol and protein, and the thickness is 20-30 nanometers. The membrane is embedded with irregular tubular fatty protein subunits, with a width of 7 ~ 15 nm and a length of 100 nm, showing a tubular surface structure.

The poxvirus, represented by aphthovirus, is oval or cylindrical, and its size is (220 ~ 300) nm× (140 ~170) nm. The core and lateral body are smaller. A long line is regularly coiled on the envelope, showing a spiral filamentous surface structure, and the envelope and filamentous structure are thicker than vaccinia virus.

Viral nucleic acid is double-stranded DNA with a molecular weight of (130 ~ 240) × 106 dalton, and the base contents of guanine (g) and cytosine (c) are particularly low, ranging from 35% to 40%. The sedimentation coefficient is about 5000S, and the floating density is 1? 1~ 1? 33 g/cm3.

There are 30 peptides with different properties in virus particles, of which 17 is related to the core. Core proteins include transcriptase, phosphonucleotide hydrolase and nuclease. The envelope of virus particles is lipoprotein, which mainly contains lecithin.

Poxvirus is not heat-resistant, but it has strong resistance in dry state. Smallpox pustule fluid is naturally dried and sealed in bottles, and its infectivity can last for several months. The virus can be isolated from smallpox crusts stored in cold and dark places 1 year. After freeze-drying, smallpox virus can be stored in the laboratory for 20 years. 60℃ 10 min can kill vaccinia virus in suspension; In the dry state, it can tolerate 100℃ 10 min, and the vaccinia titer stored at 37℃ 1 month is not affected. Ultraviolet rays, alpha rays, x rays and gamma rays can all kill vaccinia virus.

Members of orthopoxvirus and avian poxvirus have strong tolerance to ether. Treating vaccinia with ether can kill contaminated bacteria and keep the infectivity of vaccinia virus. Members of other genera are sensitive to ether. Smallpox virus and vaccinia virus are resistant to 50% neutral glycerol, phenol and common disinfectants, but sensitive to oxidants such as potassium permanganate. Vaccinia virus is sensitive to acid, and it is inactivated in suspension with pH value of 3 1 hour.

Undergraduate virus can cause diseases in humans and many animals, and can be divided into 5 groups according to natural infected hosts. Group I: only infected with humans, such as smallpox virus, infectious molluscum virus and Lenny virus; Class II: primates that infect humans and non-humans, such as monkeypox virus, Tanapox virus and Aba monkeypox virus; Class III: mammals that infect humans and non-primates, such as vaccinia virus, aphthous virus, pseudovaccinia virus, equine pox virus and bovine pustular stomatitis virus; Group ⅳ: only infected with nonhuman primates, such as white pox virus; Group ⅴ: Vertebrates only infected with non-primates, such as goat pox virus, rabbit pox virus, avian pox virus, pig pox virus, mouse pox virus, rabbit pox virus, etc.

Among poxviruses, except members of parapoxvirus and porcine poxvirus, as well as unidentified infectious molluscum virus, Tana poxvirus and Aba monkeypox virus, all of them can proliferate on the allantoic membrane of chicken embryos and form poxville. According to the shape, size and upper limit culture temperature of pox blister, many kinds of pox viruses can be identified. Smallpox virus forms tiny and dense white punctate pox blisters with obvious central uplift and borders; The scar of vaccinia virus is flat and large, with necrotic focus in the center; Vaccinia virus has acne blisters with bleeding and ulcers. The upper limit culture temperature of smallpox virus on chick embryo allantoic membrane is 38℃. Monkeypox virus 5℃, 39℃, vaccinia virus 40℃, vaccinia virus 4 1℃. The growth ability of poxvirus in cell culture is also very different. Vaccinia virus and vaccinia virus can grow in a variety of cells, leading to cell pathological changes; The cell spectrum that can grow smallpox virus is very narrow. It is difficult to culture aphthous virus and pseudovaccinia virus in HeLa cells. Infectious molluscum virus has not been successfully cultivated.

In poxvirus, only members of orthovirus genus produce hemagglutinin and have cross reaction. Hemagglutinin is a polymorphic particle containing lipids, with a diameter of 50 ~ 65 nm, which can be separated from virus particles.

variola virus

Smallpox virus is a large DNA virus, which is the pathogen of human smallpox and belongs to the genus Orthopoxvirus of Poxvirus family. There are three kinds of viruses with different virulence, namely, large smallpox, small smallpox and intermediate smallpox virus. Intermediate smallpox virus is a smallpox pathogen isolated by 196 1 in Tanzania. The virus is stable, and its virulence is between big smallpox and small smallpox.

The morphology and structure of smallpox virus are similar to vaccinia virus, but the structure of polypeptide map and gene map is different. Complement fixation test and neutralization test can not distinguish smallpox virus from vaccinia virus, but gel diffusion test or adsorption antiserum can detect the difference between them. The virus is resistant to ether and produces hemagglutinin. After injection or intranasal inoculation of smallpox virus in monkeys, it can cause mild systemic rash, but there is no death. Smallpox virus can be continuously transmitted in the brain of suckling mice, and its toxicity to mice is lower than that of vaccinia virus.

Smallpox has no animal storage host and vector insects, and patients are the only source of infection. The patient is not contagious during the incubation period. When a rash occurs, the patient's respiratory tract and oral secretions contain a large number of viruses, which are excreted with deep breathing actions such as coughing, sneezing and talking loudly, polluting the air and articles; The patient's blister fluid can also contaminate clothes and bedding. Smallpox virus has a strong resistance to the external environment, and can remain contagious in scabs, articles and even in the air for a long time. It spreads through direct contact with patients or indirect contact with contaminated items. In direct contact, it is mainly spread by air aerosol in respiratory tract. Smallpox virus can also spread far away with the air, causing infection. People are generally prone to smallpox, but they can get good immunity after getting sick or vaccinated with vaccinia, and generally can no longer be infected.

Smallpox is clinically divided into four types. ① Ordinary smallpox: the rash is distributed centrifugally and goes through four stages: papule, blister, pustule and scab; It accounts for 85% of the total smallpox. ② Deformity pox: It occurs in people who have been vaccinated with pox. The rash develops rapidly but is atypical, with a small number and superficial appearance, accounting for about 5% ~ 7%. ③ Flat smallpox: The rash is flat, soft to the touch, develops slowly, does not form pustules, and usually kills, accounting for about 5% ~ 7%. ④ Hemorrhagic smallpox: The skin and mucous membrane bleeding is serious, and it usually dies suddenly within 5-7 days, accounting for only 65,438+0%.

There are three commonly used laboratory diagnosis methods. ① Direct smear staining and microscopic examination: Virus particles were stained dark brown by silver plating on a light yellow background. ② Gel precipitation test: If enough virus materials are taken, precipitation lines will appear in the gel containing high-valent immune serum within 2 hours. ③ Virus isolation: Inoculate the materials to be tested with chick embryo allantoic membrane, and the results can be obtained after 72 hours.

Universal vaccination is the most effective prevention and control measure. Due to the worldwide vaccination campaign, the spread of smallpox among people has stopped since June 6.

Vaccinia virus

Vaccinia virus is a large DNA virus, belonging to the genus Orthopoxvirus of Poxvirus family. It is used for smallpox vaccination in laboratory by animal culture, chicken embryo culture or cell culture. Because vaccinia virus has been used for a long time, its exact source is not clear; However, the hybrid of smallpox-vaccinia virus obtained by hybridization in the laboratory has been proved to have the characteristics of vaccinia virus.

Vaccinia virus hosts a wide range, except humans, calves, sheep, rabbits, monkeys, mice and guinea pigs are all susceptible animals. Chicken embryos can be infected by various ways, and the spectrum of cells that can grow is also very wide. Vaccinia virus has strong adaptability to the living environment and is easy to induce mutation in the laboratory. For example, skin vaccinia virus can obtain neurotropic properties after continuous passage in rabbit brain or mouse brain; Continuous passage in cell culture can reduce the toxicity to animals and lose the ability to produce hemagglutinin; The mutant strain obtained by lowering the cell culture temperature has significant changes in the shape of blain blister on chick embryo allantoic membrane and its sensitivity to temperature.

In antigenicity, vaccinia virus is closely related to smallpox virus, and vaccination can prevent smallpox. After vaccination with vaccinia virus, the human body only causes a local infection process at the inoculation site, thus gaining immunity. However, if the virulence of vaccinia virus is too strong, the immune function of the recipient is defective, or the contraindications are not strictly controlled when vaccinating, various complications may occur.

The pox slurry at the inoculation site is transplanted to other skin or mucosal parts of the body, which can cause local vaccinia virus infection. If transplanted to the eyelid, papules or ulcers of different sizes can be formed at the edge of the eyelid, leading to keratitis and even blindness. Eczema patients inoculated with or exposed to vaccinia can cause infection in eczema parts and healthy skin, and blisters of acne and pimples often merge into pieces, which can be fatal in severe cases. If the humoral immune response of the recipient is slow, vaccinia virus can spread to the whole body through blood circulation, which can cause systemic vaccinia virus infection. If the recipient's cellular immune function is defective, it can cause progressive vaccinia virus infection, and acne blisters continue to grow and will not heal for a long time. The center of acne blister is obviously necrotic, and the edge is Bai Causeway-shaped. Similar acne blisters can also appear in other parts of the body. Although this infection is rare, the mortality rate is extremely high. The first vaccination of pregnant women can also lead to systemic vaccinia virus infection in the fetus, resulting in stillbirth or death in a short time after delivery.

Treatment of vaccinia virus infection, intramuscular injection of high-priced vaccinia immunoglobulin, or transfusion of plasma or whole blood with recent successful vaccinia. Injecting leukocyte or lymph node suspension from recently successful vaccinia patients around the focus infected by progressive vaccinia virus can make the ulcer heal quickly.

Monkeypox virus

Monkeypox virus is a large DNA virus, which is the pathogen of monkeypox and belongs to the genus Orthopoxvirus of Poxvirudae. Serologically related to smallpox virus and vaccinia virus. It contains specific monkeypox antigen, and the pox blister formed on the allantoic membrane of chicken embryo is pink due to bleeding. It can be handed down from rabbit skin. It is highly toxic to mice and chicken embryos. It does not proliferate on porcine embryonic kidney cells.

1970, a case of monkeypox was first discovered in Zaire [now Democratic Republic of Congo]. Human infection with monkeypox virus can cause systemic acne rash, which can not be distinguished from smallpox in clinic, and there will be permanent scars after recovery. The mortality rate can reach 17%. Monkeypox virus is difficult to spread from person to person, and the incidence of second-generation cases is very low among susceptible people in close contact.

Monkeypox cases mainly occur in tropical rain forests in central and western Africa, where residents have the habit of raising monkeys and eating monkey meat. Vaccination can prevent monkeypox virus infection.

Infectious molluscum virus

Infectious soft wart virus is a large DNA virus and the pathogen of infectious soft wart, belonging to Poxvirus family (genus undetermined). The morphology and structure of infectious molluscum virus are similar to vaccinia virus, but there is no serological connection. It does not proliferate on the allantoic membrane of chicken embryo, and the infection of experimental animals is unsuccessful. Cytopathy can be seen on human foreskin and human amniotic cells, but it can not be passed on. Antibodies can be detected by gel precipitation test and immunofluorescence technique.

After people are infected with infectious molluscum virus, scattered nodules of 2 ~ 5 mm appear on all skin surfaces except hands and feet, with hundreds of nodules, which are pearl-colored and painless. There is a small hole at the top of the nodule, and the white nucleus pulposus can be seen inside. The cells in the nodule are unusually large and contain large and transparent eosinophilic cytoplasm blocks, which are called molluscum. Mollusks are divided into many cavities by sponge-like matrix, and the virus particles in the cavities gather into clusters. The infection will last for several months.

As a known natural host, human beings can be infected at all ages, especially children. Distributed all over the world, spread through direct contact or indirect contact.

Marburg virus

The clinical manifestations of acute infectious diseases caused by it are high fever, headache, general pain, diarrhea and rash. 1967 is the first epidemic among laboratory workers in Marburg, Federal Republic of Germany, with 3 1 case. Among them, 25 primary cases were laboratory workers who had been exposed to the Changkun green monkey imported from Uganda, Africa, and 7 cases died. There were 6 secondary cases without death. Therefore, this disease is called Marburg disease or green monkey disease. In addition, in 1975, another case of 1 occurred in Johannesburg, South Africa, and they died without touching monkeys. Two cases of secondary cases were cured.

Under the electron microscope, the virus particles are curved strips, filaments or columns, curled or branched, and the two ends are hooked, horseshoe-shaped or bubble-shaped. The diameter is 65 ~ 90 nm, and the length 130 ~ 2600 nm (average 665 nm). The internal structure is a spiral core with a diameter of 45 nanometers. The outer part is a coating with surface protrusions, with a thickness of 20 nanometers. There are horizontal stripes at intervals of 5 nanometers.

After 5 weeks at room temperature or 4℃, the virus titer rarely decreased, but it decreased obviously after 8 weeks. After several years of storage at -70℃, the infectivity does not decrease. The virus can be inactivated at 60℃ for 30 minutes or 56℃ for 60 minutes. Sensitive to ether, chloroform and deoxycholic acid. At room temperature, 10% formalin can make the virus lose infectivity 1 hour. 1 ∶ 2 000 β。 Propylene lactone can inactivate the virus for 24 hours. The antigen composition is unknown. Contains lipoprotein. No hemagglutinin and hemolysin. Can be neutralized by specific antiserum. Culture infected animal organs or tissues to prepare complement binding antigen. Virus antigens can be detected by direct or indirect immunofluorescence.

Marburg virus was originally isolated by intraperitoneal inoculation in guinea pigs. The vaccinated guinea pigs developed high fever and recovered after 10 days. After passage, the condition worsened and the mortality rate was high. The blood virus concentration of the third generation guinea pigs reached 106ID50//ml. It can infect macaques and rhesus monkeys in South Africa, causing viremia, fever and serious diseases, and die after 5 to 25 days. The virus concentration in urine reached 106ID50//ml. The contact between monkeys is contagious, and/kloc-0 died after 5 ~ 36 days. It can also be spread by aerosol. Guinea pigs can adapt to hamsters after 9 generations, and monkeys can adapt to hamsters after 3 generations. After 9 generations of hamster transmission, neonatal rats developed fatal encephalitis. After three generations of hamster transmission, newborn mice were inoculated and died of encephalitis within 3 ~ 4 weeks. Intracytoplasmic inclusions were found in brain lesions. The virus can be passaged by intrathoracic inoculation with Aedes aegypti. Virus proliferation in infected animals can be determined by virus isolation, immunofluorescence technique, electron microscope observation and antibody detection.

The virus can be replicated in primary cultures of South African monkey kidney, rhesus monkey kidney, human amniotic membrane, chicken fibroblasts and guinea pig fibroblasts. After continuous passage in the culture of AH- 1, Vero cell line, BHK2 1 cell line and human lung fibroblasts, cytopathic effects can be produced, but not completely. It can also be replicated in LLC-MK2 cell line, L cell line from mouse fetus, guinea pig heart cell, HeLa cell line, human lung diploid cell line and human foreskin fibroblast culture. Inclusion bodies are formed in cytoplasm. Immunofluorescence technique can be used to detect virus titer. The titer of the third generation virus in Vero cell line is 105? 5~ 106? 5ID50//ml。

As mentioned earlier, there were 34 cases of Marburg disease in two epidemics. The first epidemic occurred from July 20th to August 60th. 1967. 500 ~ 600 green monkeys were airlifted from Uganda to three research institutions in Marburg, Frankfurt and Belgrade, Yugoslavia. All the cases occurred were people who had contacted the blood of green monkeys or their organs (especially kidneys). Of the 29 people who had their organs removed by surgery, 20 were ill. 15 people who do tissue culture, 5 are sick. Six cases got sick due to contact with these patients. The route of transmission can be through damaged skin or mucous membrane, or through the bite of Aedes aegypti. The infectious agent is usually blood in fever period, or it may be something that has been in contact with patients. There were 1 person who infected their wives through semen after onset 12 weeks. Pharyngeal secretions and urine only have low concentrations of virus. The second epidemic occurred in February 1975. Three people were sick in Johannesburg, South Africa. 1 The case is a short-term tourist in Rhodesia who has never been in contact with monkeys and was bitten by insects while camping. On the 7th day after onset, his companion became ill. He was also infected with 1 nurse who cared for him, and the incubation period was 7 days. The source of Marburg disease is still unknown. The transmission route is directly related to the long-tailed green monkey, but it is still uncertain that it is a natural storage host. So far, there is no evidence to prove which animal or insect is the storage host or transmission medium.

There are only two epidemic reports in humans. No reinfection cases were found. Guinea pigs infected with this virus and surviving no longer have fever after being attacked again, indicating that they have acquired immunity. Both patients and infected animals produce neutralizing antibodies, complement-binding antibodies and antibodies measured by immunofluorescence tests. Complement-binding antibody usually reaches its peak after 1 ~ 2 weeks of infection, and begins to decline at the eighth week. After 2 years, low level antibody can still be detected. The antibody measured by immunofluorescence test reached its peak at 1 ~ 2 weeks after onset, and its titer was 4 times higher than that of complement-binding antibody, and it decreased slowly, and it still had a high titer after 8 years. There is no satisfactory method to detect neutralizing antibodies. Antibodies can be transmitted through the placenta, and this passive immunity disappears within 3 months.

The incubation period of Marburg disease is 3 ~ 9 days, and the onset is sudden. The early symptoms are high fever, severe headache, conjunctival congestion, general pain and fatigue. Later, nausea and vomiting occurred, followed by a large number of watery diarrhea. On the 4th or 5th day of onset, special maculopapules appeared on the skin, which quickly merged into diffuse erythema, mostly on the buttocks, trunk and outside limbs. The rash disappeared on day 10, and the limbs, palms and soles peeled off two weeks later. In the first epidemic, the patient's soft palate and hard palate appeared crimson mucosal rash. The fever is as high as 38 ~ 40℃ for 5 ~ 7 days. On the 5th to 7th day after illness, some patients developed bleeding, most commonly gastrointestinal or pulmonary bleeding. Severe cases have central nervous system damage. Cases in South Africa are complicated with hepatitis and liver failure, accompanied by disseminated intravascular coagulation. In severe cases, cachexia, massive hemorrhage, anuria and shock appeared quickly before death. The acute phase lasts 14 ~ 16 days, and then it enters the recovery period. Slow recovery, periodic headache, alopecia. Early leukopenia and thrombocytopenia, prolonged coagulation time. Fibrinogen and transaminase increased.

Diagnosis can be made by complement fixation test or immunofluorescence technique to detect serum antibodies in rice recovery period in acute stage. Viruses were isolated from blood or tissues such as liver, spleen, kidney, lymph nodes, heart and lung by intraperitoneal inoculation or Vero cell culture in guinea pigs. The virus particles in blood, liver and other materials were examined by electron microscope, and the virus antigen in cytoplasm was detected by immunofluorescence technique after the materials were inoculated into cells for culture. Examine the cytoplasmic contents in liver tissue sections.

Prevention should avoid contact with infected animals. Take strict isolation measures for patients. Thoroughly poison the polluted environment and articles. There is no specific therapy. Plasma injection or supportive therapy can be used in the recovery period. Matters needing attention in knowledge point inoculation

Vaccination requires aseptic operation, and the inoculation place should be kept clean to avoid scratches. Vaccination should not splash on eyes and mouth or pollute the skin in other places. Pay attention to the batch number of vaccinia, and don't check the batch number if there is too much reaction. Avoid vaccination under the following circumstances:

(1) People with eczema or allergic constitution, or those with neurodermatitis, pyoderma, chickenpox, eruptive diseases, herpes simplex and other skin diseases.

(2) Immunodeficiency such as physiological hypogammaglobulinemia, abnormal gammaglobulinemia, malignant tumor, temporary or permanent immune damage caused by any disease, and treatment with hormones and immunosuppression.

(3) Family history of nervous system diseases, such as convulsion, stroke, encephalitis after vaccination, and any chronic, static or progressive nervous system diseases.

(4) Acute fever and β hemolytic streptococcus infection.

(5) The first vaccination of pregnant women, especially within 3 months of pregnancy, can cause fatal systemic vaccinia rash of the fetus, so the first vaccination during pregnancy is prohibited. A deadly ghost. A deadly ghost.