Parvovirus infection

Introduction to microvirus infection Human parvovirus infection is a group of diseases that have been gradually recognized for more than 20 years. The clinical manifestations may include general symptoms of viremia, as well as special manifestations of infectious erythema, vascular purpura, joint disease, and numbness. Pregnant women can cause intrauterine infection after infection, leading to fetal anemia, edema and death. Aplastic anemia crisis (aplastic anemia) can occur in patients with hemolytic anemia. The disease is acutely self-limiting. The process has a good prognosis, but the immunodeficiency can be chronically delayed. In recent years, there have been several reports of death due to fulminant myocarditis and fulminant hepatitis. basic knowledge Sickness ratio: 8% Susceptible people: no special people Mode of infection: contact spread Complications: anemia heart failure

The cause of microvirus infection

Viral infection (75%):

Microviruses are currently the smallest known DNA viruses. It has long been known that parvoviruses can cause diseases in small mammals. It has only been known for nearly 20 years that some of them can infect humans and cause disease. In 1975, Cossart first served blood in blood donors. A round virus particle with a diameter of 20-25 nm was found. The morphological, biochemical, and genetic characteristics of the virus belonged to the microvirus, named human microvirus B19. Soon, the virus was found in the blood of two fever soldiers. The pathogenicity of the virus to humans, the virus has a naked nucleocapsid containing a single strand of DNA, which is 5.45 kb in size and has the ability to replicate autonomously. In 1981, the blood of a child with aplastic anemia from sickle cell anemia B19 antigen was detected in the following years. In the following years, B19 antigen was detected from the blood of patients with aplastic anemia, infectious erythema and purpura in Canada, Japan, Britain, Sweden and the United States. P19 and these diseases were initially considered. In 1985, Anderson et al reported the results of an infection test conducted on 7 volunteers with B19, further affirming that HPV B19 is the causative agent of these diseases, and the virus has no tissue culture yet. Growth replication in human bone marrow cells, heat, 60 12h can not be inactivated, formaldehyde sensitive.

Pathogenesis

Anderson conducted experiments on volunteers. Seven volunteers received HPV-B19 DNA in the blood of 5 subjects without antibody in the blood for 6-7 days after nasal inoculation of B19 virus. The amount of virus reached on days 8-9. At the peak, 1011 genomic copies/ml were detected, 3 of which were detected in the nasal and pharyngeal sputum, IgM antibodies were present at the 2nd week, and IgG antibodies were present at the 2nd and 3rd weeks. The viremia lasted for about 1 week. At this time, the subject developed fever and general malaise. After 2 to 3 days, the rash appeared, followed by joint pain, and the hemoglobin decreased. The daily reduction was 13-18 g/L, and the reticulocyte count was obvious. Reduced, white blood cells and platelets also have a slight decrease, blood changes can be restored after 1 week. Two subjects with anti-B19 IgG antibodies in the original blood were asymptomatic, and B19 DNA was not detected in the blood. The serum of patients with symptoms can inhibit the formation of red blood cell colonies in vitro. The serum can not be inactivated by heating at 56 °C for 30 minutes. Bone marrow examination of patients with aplastic anemia is found to significantly reduce the red blood cell line, and other cell lines have no major changes. Therefore, the virus is mainly caused by the invasion of bone. The red blood cell line in the myeloid hematopoietic system, the erythroblasts in the primitive stage may be the main target cells, and the glucoside on the red blood cells is a viral receptor. After the virus is infected, the red blood cells can be lysed, thus causing the red blood cells to decrease. The inhibition of bone marrow hematopoietic function lasts for 1 week, and may have a slight effect on normal hematopoietic function. However, patients with hemolytic anemia with shortened red blood cell life may have a possibility of causing aplastic anemia. In addition, the virus may invade the body. Organs and tissues, B19 DNA has been detected from the heart, brain, liver, kidney, lung, spleen and other tissues of people who have been seriously infected with B19; electron microscopy has seen a virus arranged in the myocardium of the myocardium; The rash is found to have a virus in vascular endothelial cells, sweat glands and ductal epithelial cells, so the virus may have a direct pathogenic effect. In addition, B19 virus infection may cause the production of cytokines such as interferon gamma, IgM and IgG specific. The appearance of sexual antibodies can cause immune-mediated pathological changes, joint disease may be caused by immune complexes, many studies have proved the back of B19 infection Patients may be chronically ill and/or carry a long-term virus, and the immune function is low. The immune function is also normal, and the cause is still unclear. Some people have detected B19 DNA from the bone marrow of healthy donors. Therefore, it is possible that the bone marrow is a place where the B19 virus survives for a long time.

Microvirus infection prevention

prevention

1. The natural route of transmission of HPVBI9 is currently unknown. The simultaneous outbreak of red blood cell hypoplasia and EI suggests that exposure increases the risk of transmission. Since the respiratory tract and saliva have HPVBI9 excretion after inoculation, there may be aerosol spread and human-to-human hand-carrying.

2. Some people also believe that there may be a spread of the digestive tract and the route of injection.

3. The vaccines have been developed for animal testing and are expected to be used for prevention in the future.

Microviral infection complications Complications anemia heart failure

Intrauterine infection can cause fetal anemia, hypoxia, and heart failure.

Symptoms of parvovirus infection Common symptoms Abdominal pain Muscle pain Sore throat Ascites joint pain Joint effusion Freckle platelet Reduction Hemolytic anemia Red blood cell increase

In the epidemic, there may be 20% asymptomatic infection, the incubation period is 1 to 2 weeks, the patient has sore throat, mild cough, rhinitis and other symptoms, accompanied by systemic symptoms such as general malaise, muscle pain, low fever, and some patients only continue 2 to 3 days is good, more patients than the epidemic area can be diagnosed by pathogen or immunological examination. In addition, the virus can cause the following diseases with different clinical manifestations.

1. Erythrocyte aplastic crisis:

This disease is a disease caused by HPV-B19 infection in patients with hemolytic anemia. It is more common in children. Patients have fever (mostly low to moderate), general malaise, burnout, myalgia, headache, and mild cough. After 2 to 3 days, the number of reticulocytes began to decrease, hemoglobin decreased, and some patients had a slight decrease in white blood cells and platelets. Hemoglobin can be reduced by 20 to 50 g/L, resulting in more obvious symptoms of anemia: palpitations, paleness, weakness, severe Blood transfusion is required. With the disappearance of viremia, the production of specific antibodies, and the inhibition of bone marrow hematopoietic function are alleviated. The blood picture of the patient can be restored to the original level after 1 week, and the immune function defect can cause chronic bone marrow dysfunction. And caused a long-term anemia, there is a 27-year-old male black, anemia has lasted for 13 years, another 27-month-old baby, repeated acute episodes 3 times in a year, aplastic anemia enhanced immune function treatment Can be relieved, this aplastic anemia can occur in sickle cell anemia, globin-forming anemia, hereditary elliptic polycythemia, autoimmune hemolysis Anemia, pyruvate kinase deficiency, and hereditary disorders such multinucleated immature cells.

2. Skin, vascular damage disease:

(1) vascular purpura: patients with children, but also adults, first appeared fever, sore throat, salivation, etc., 48h after the appearance of rash, characterized by vascular purpura, first appeared in the limbs, back to the trunk, The neck and even the face expand, the purpura persists for several days, and may be accompanied by short-term leukopenia and thrombocytopenia. Some patients have abdominal pain or large joint pain. Histological examination has necrotizing vasculitis and non-necrotic vasculitis.

(2) Infectious erythema (erythema infectiosum): This disease is also known as the fifth disease. In 1889, Tschamer has described the disease in detail. It has been popular in many parts of the world. It was not until 1981 that HPV-B19 was identified. pathogen.

The clinical manifestations of infectious erythema in children, first fever, general malaise, sore throat, nasal sputum and other symptoms, rash after 2 to 3 days, mostly start from the face, and soon merge into a piece with mild edema, forming "Slap face" special performance, the rash quickly spread to the trunk and limbs, first for the maculopapular rash, after the middle faded to form a mesh or lace-like, the rash can be aggravated by the sun, exercise, bathing, accompanied by itching, continuous 2 to 4 days, the rash subsides, leaving pigmentation to resolve in a few days, the whole course of disease is 5 to 9 days.

There are also a few cases of HPV-B19 in adults with infectious erythema, but there are few "slaps of the face" and rashes are rare, but 80% of people have joint pain within a few days to weeks after the illness.

(3) acropetechial syndrome:

In 1990, Harms et al reported for the first time that 5 cases of sclerotherapy with glove-like sleeve distribution and oropharyngeal ulcer were found. The pathogen was unknown. In 1992, the same patients appeared in the United States. Halasz et al. were specifically caused by B19 virus. In 1998, Smith et al analyzed. The clinical manifestations of 25 patients reported in various places, called papular-purpuric gloves and socks syndrome, were performed by Harel et al in 2002 based on the performance of their own 3 patients. The clinical symptoms are called acne freckle syndrome. The clinical manifestations include mild or moderate fever, general malaise, joint pain, myalgia, poor appetite and other systemic symptoms. Sexual rash, which develops quickly to the palm surface. It can be fused into a piece. There are obvious boundaries between the wrist and the ankle. At the same time, there may be lip edema, perioral erosion, rash around the mouth and lower jaw, and pharyngeal fistula may have Mucosal sputum, composed of hand, foot, mouth disease-like syndrome, disease more than 1 to 2 weeks of recovery, the patient's serum first appeared B19 IgM antibody, IgG antibody appeared later, rash histological examination visible dermal blood Surrounded by infiltration, extravasation of red blood cells, patients were mostly young people.

(4) Rayhad's pnenomenon:

Harel et al. reported in 2000 that two sisters (13 years old, 14 years old) had their fingers, white toes, cold, and then cyanosis, 1 case with general joint pain, and strong B19 IgM in serum. Could not find other reasons.

3. Arthropathy:

In the various clinical manifestations of HPV-B19 infection, some patients have joint pain; some patients have fever, general malaise, only joint pain; some patients have joint pain as the only symptom, the disease is less children, adults More, and more common in women, more manifested as sudden limb joint symmetry pain, may be associated with varying degrees of joint sac swell, the most common hand (knuckle, metacarpophalangeal joint), wrist, ankle, knee Joints can also involve elbows, shoulders, cervical vertebrae, lumbar vertebrae, etc. Most of them can be improved in about 2 weeks. A few patients have been unhealed for several weeks. The disease has been reported for 4 years. A patient has been examined for white blood cells in the joint effusion. 3.4 × 109 / L, 42% of multinucleated cells, 58% of monocytes, follow-up observation without sequelae and dyskinesia, diagnosis based on anti-HPV-B19 IgM antibody positive in patients' serum, failed to detect HPV-B19 DNA and antigen, so It is speculated that the disease is caused by the virus antigen-antibody complex, but Soderlund et al reported that B19 DNA was detected in the synovial tissue of some juvenile chronic arthritis patients, and the direct damage of the virus could not be excluded.

4. Limb numbness, stinging pain:

It has been reported that 11 cases of nursing staff were also infected when a contagious erythema in a children's hospital in the United States was infected. Five of them had finger and/or toe numbness and tingling symptoms, and the other two had no other discomfort. Only the fingers were numb. Pain, anti-HPV-B19 IgM antibody in the blood, some patients recovered at 2 months, partially delayed to 1 year, the symptoms were obvious, the muscle strength was weakened, the nerve conduction velocity was slowed, suggesting that the peripheral nerve was damaged, and there was 1 immunity. Normally functioning nurses, B19 viremia persisted for 4 years (HPV-B19 DNA positive) after typical onset, and there were 6 episodes: fever, rash, joint pain, distal numbness of the extremities, stinging, acral during remission There is still migratory numbness, and this patient apparently presents with chronic persistent B19 infection, the cause of which is unclear.

5. Intrauterine infection:

Pregnant women infected with HPV-B19 can be transmitted to the fetus, easily cause abortion and stillbirth, HPV-B19 DNA has been detected from the heart, liver, spleen, kidney, lung and other cells of the stillbirth, some have found the virus particles, the fetus is obviously anemia , high edema, may have pericardium, chest, ascites, the incidence of various reports vary, a group of 38% (14/37), the United Kingdom reported 9.8%, the US CDC reported 4%, micro-virus infected animals It can cause teratogenicity. Whether humans are teratogenic or not is not certain. There are only a few reports (the absence of fetal lens crystals), and more research is needed.

6. Other diseases:

B19 virus can invade a variety of organs and tissues throughout the body, so it can cause a variety of diseases. 1 Myocarditis: mostly infants and children, acute fulminant manifestations, and soon die of heart failure, there are people who have a heart transplant, and also In patients with chronic myocarditis, myocardial infiltrating inflammation, 2 acute hepatitis: liver function may have varying degrees of impaired performance, B19 infection after liver transplantation can cause acute fulminant hepatitis and aplastic anemia, 3 meningitis There have been several clinical reports of aseptic meningitis, detection of B19 DNA from CSF (cerebrospinal fluid), 4 cases of respiratory distress, Still disease, chronic fatigue syndrome and other clinical manifestations. No pathogens were found except for B19 DNA or specific IgM antibodies.

Microvirus infection check

1. Blood examination: Peripheral blood leukocytes can be mildly reduced or normal, and hemoglobin and platelets can be reduced in people with aplastic anemia.

2. B19 DNA test: PCR method can detect DNA from patient serum, CSF and diseased tissue, which is a means of diagnosis.

3. Immunological examination: B19 antigen can be detected by radioimmunoassay or ELISA, and more IgM antibodies for B19 can be detected. The disease can reach a peak at 1 week, and it will decrease after 2 months. The diagnostic value of the current infection, IgG antibodies appear later, lasting for a long time, have a protective effect.

4. Acute myocarditis or pericarditis infection: ECG abnormalities may occur.

Diagnostic identification of parvovirus infection

diagnosis

Infectious erythema, vascular purpura and other diseases are prevalent in some areas, and have a history of contact with patients, can be used as a reference for diagnosis, clinical fever, especially in patients with rash should consider the possibility of the virus infection, hemolytic Patients with anemia should consider the possibility of the disease when they have aplastic anemia. The diagnosis must be carried out by pathogen and immunological examination. B19 DNA in blood can be detected by dot blot or PCR, and B19 antigen can be detected by RIA (radioimmunoassay). Specific IgM antibodies can be detected at 1 week of disease, and it is also meaningful to change the IgG antibody from negative to positive.

Differential diagnosis

Need to be differentiated from scarlet fever, rubella, and light measles.

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