Dengue

Introduction to dengue fever Dengue fever (denguefever) is an acute infectious disease caused by dengue virus transmitted by Aedes mosquitoes. It is characterized by acute onset, fever, general muscle, bone, joint pain, extreme fatigue, rash, swollen lymph nodes and blood white blood cells. Thrombocytopenia. Patients and people with latent infection are the main source of infection. The patient was most contagious within 1 day from the onset of the disease to 3 days after the onset of the disease. A small number of patients can also isolate the virus from the blood on the third day after the heat withdrawal. In addition, dengue virus antibodies can be detected in animals such as bats, monkeys, birds and dogs, which may be the natural host of dengue virus, which may become a source of infection for this disease. basic knowledge The proportion of sickness: 0.05%-0.07% (high incidence of forest workers) Susceptible people: no specific population Mode of transmission: insect vector transmission Complications: myocarditis, arrhythmia, uremia, liver and kidney syndrome

The cause of dengue fever

(1) Causes of the disease

1. Source of infection: Patients and patients with latent infection are the main source of infection. No healthy virus carriers are found. The patient has obvious viremia from 6 to 8 hours before the onset to the 6th day of the disease, which can cause Aedes to be bitten. During the epidemics, the number of light patients is 10 times that of typical patients, and the recessive infection is 1/3 of the population. It may be an important source of infection. Monkeys in the jungle mountains and some livestock in the city have serum infected with dengue virus. Learning evidence, but as a source of infection, has not yet been determined.

2, the media: Aedes mosquitoes, 12 species of Aedes mosquitoes are known to spread the disease, but the most important are Aedes aegypti and Aedes aegypti, Guangdong, Guangxi is mostly transmitted by Aedes albopictus, and Leizhou Peninsula, Guangxi coast, In Hainan Province and Southeast Asia, Aedes aegypti is the main species. Aedes mosquito can get infection if it is in contact with infectious liquid once. The virus is contagious after being replicated in mosquitoes for 8-14 days. On the 174th, when the infectious Aedes mosquito bites the human body, the virus is transmitted to humans. Because the dengue virus particles are detected in the ovaries of Aedes aegypti, it is speculated that Aedes mosquito may be the storage host of the virus.

3, susceptible population: widespread in the new epidemic area, in the 1980 epidemic in Guangdong, the minimum age of 3 months, the largest 86 years old, but the highest incidence of young adults, in endemic areas, residents over 20 years old 100% of the neutralizing antibodies against dengue virus can be detected in serum, and the majority of the cases are children.

(two) pathogenesis

The dengue virus replicates in the capillary endothelial cells and the mononuclear macrophage system after being bitten into the human body by the Aedes mosquito, and then enters the blood circulation to form the first viremia, which is localized in the mononuclear macrophage system and lymphoid tissues. The dengue virus continues to replicate, and is released into the bloodstream to form a second viremia, causing clinical signs and symptoms. The anti-dengue virus antibody produced by the body forms an immune complex with the dengue virus and activates the complement system, resulting in Increased permeability of blood vessels can also lead to edema and rupture of the blood vessels. Replication of dengue virus can inhibit the regeneration of white blood cells and platelets in the bone marrow, leading to white blood cells, thrombocytopenia and bleeding tendency.

Pathological changes manifested as degeneration of organs such as liver, kidney, heart and brain, and edema and hemorrhage of endocardial, pericardium, pleura, peritoneum, gastrointestinal mucosa, muscle, skin and central nervous system, rash biopsy visible Small vascular endothelial cells are swollen, perivascular edema and mononuclear cell infiltration, extensive extravascular hemorrhage in ecchymosis, subarachnoid and brain parenchymal hemorrhage, cerebral edema and brain softening in patients with meningoencephalitis There may be central necrosis of the hepatic lobules and cholestatic, lobular pneumonia and interstitial pneumonia.

Dengue prevention

First, prevention of dengue fever should deal with the breeding ground and eliminate mosquitoes:

1. Dredge the ditches and sewers to prevent stagnant water, fill the ground, turn over the pots, and remove the accumulated water.

2. Try to avoid planting plants with clear water. For vases and other containers, wash and change water at least once a week. Do not leave water in the flowerpot chassis. Put all used cans and bottles in a covered trash can to destroy the Aedes albopictus breeding ground.

Second, prevention of dengue fever to kill adult mosquitoes: in residential, office, hospitals and other public places can use drugs to kill adult mosquitoes. The following types are currently available:

1, dichlorvos: the use of drug dilution spray and smoke, characterized by quick-acting, rapid killing of adult mosquitoes. It is toxic to humans and animals. Be careful when using it and pay attention to safety.

2, triclosan (7504): low toxicity to humans and animals, can be diluted with drugs and smoke, characterized by slow effect, but long-lasting, 7 to 10 days is still effective. Can be mixed with dichlorvos in a ratio of 4:1 or 3:1, which has the advantage of being fast and lasting for a long time.

3, artificial pyrethroids: its preparations are permethrin, methrin, etc., can be diluted with drugs, characterized by strong insecticidal effect, low toxicity to humans and animals.

4, deltamethrin: belongs to the contact drug (ie contact poisoning) can be diluted with drugs spray, strong insecticidal effect, low toxicity to humans and animals.

Dengue complications Complications myocarditis arrhythmia uremia liver and kidney syndrome

1, acute intravascular hemolysis: the most common, the incidence rate is about 1%, mostly in patients with defects in glucose-6-phosphatase dehydrogenase (G6PD) in red blood cells, mainly as a soy sauce Urination, anemia, shortness of breath, rapid heart rate, urine specimens have no or only a small amount of red blood cells and the occult blood test is strongly positive. It is worth noting that when acute intravascular hemolysis occurs, the blood G6PD content can be in the normal range, but at 1 After a month, the content defect occurs. This is because when the acute intravascular hemolysis occurs, the G6PD deficiency in the blood matures, the aging red blood cells have been lysed, and the rest are young red blood cells with relatively high G6PD content. When they mature, aging The G6PD defect gradually appeared.

2, mental disorders: individual patients can be complicated by infectious psychosis, especially in patients with a family history of mental illness.

3, myocarditis: severe cases can occur myocarditis, mainly manifested as heartbeat, shortness of breath, increased heart rate, arrhythmia can occur.

4, liver function damage: mild liver damage is common, mainly manifested as mild hepatic swelling, sharp edges, soft, liver function tests showed ALT, AST and -glutamyltranspeptidase (-GT) Elevated, severe cases can cause elevated total bilirubin (TBIL), and even hepatorenal syndrome.

5, uremia: more common in patients with dengue hemorrhagic fever, massive bleeding or acute intravascular hemolysis can promote the occurrence of uremia.

6, acute respiratory distress syndrome: acute respiratory distress syndrome (ARDS) can be seen in patients with severe and dengue hemorrhagic fever, manifested as shortness of breath, distress, irritability, cyanosis, both lungs can be dry, wet voice, arterial blood gas analysis Arterial partial pressure of oxygen (Pa02) <8.0kPa (60mmHg), early arterial blood carbon dioxide partial pressure (PaC02) is often <4.7kPa (35mmHg), and late PaCO2 can be >6.0kPa (45mmHg).

7, other: Other possible complications include intracranial hypertension, acute disseminated encephalomyelitis (ADEM), infectious polyradiculitis and uveitis.

Dengue symptoms common symptoms high fever chills lymph nodes swollen gums gingival bleeding persistent fever twitch joint pain systemic vascular damage bleeding tendency

The incubation period is 3 to 15 days, usually 5 to 8 days.

The World Health Organization divides dengue virus infectious diseases into dengue fever and dengue hemorrhagic fever. Clinically, dengue fever is divided into typical, light and heavy. Dengue hemorrhagic fever is divided into no-dengue hemorrhagic fever (DHF). And dengue shock syndrome (DSS).

1, typical (ordinary) dengue fever

(1) Fever: usually a sudden onset of illness, chills or chills, high fever, body temperature rises to 39 ~ 40 °C within 24 ~ 36h, most patients show the heat of retention or relaxation, most patients after 5 to 7 days of treatment, The body temperature gradually returned to normal level. A few patients fell to normal after 3 to 5 days of fever, and then rose again after 1 day. It was called bimodal fever or saddle fever. Frequently accompanied by severe headache, eye pain, muscle, Bone and joint pain, extremely weak, may have nausea, vomiting, abdominal pain, diarrhea or constipation and other gastrointestinal symptoms, the patient's breathing during the fever period, pulse speed, early signs of facial, neck, chest skin flushing, ocular membrane congestion And superficial lymph node enlargement, the recovery period is often significantly weakened and it takes several weeks to fully return to normal. The child's case can be slower onset, the symptoms of venom are lighter, and the recovery is often faster.

(2) rash: often appears on the 3rd to 6th day of the disease course, mostly rash, can be measles-like rash, scarlet fever-like rash, red spot rash and hemorrhagic rash (defect), etc. Two or more rashes appear. The rash is first seen on the trunk, then gradually spread to the limbs, the head and face, and finally distributed on the whole body skin. The rash is mostly itchy, most of which does not desquamate, and gradually subsides after 3 to 5 days.

(3) Bleeding: bleeding occurs mostly on the 5th to 8th day of the disease course, and 25% to 50% of typical cases have different degrees of bleeding, such as subcutaneous hemorrhage, bleeding gums, nosebleeds, skin, submucosal bleeding, etc. The size of the bleeding range is positively correlated with the severity of the disease. The diameter of the skin or submucosal hemorrhage is not more than 2 mm, which is called the bleeding point. The diameter of 3 to 5 mm is called purpura, and the diameter of 5 mm or more is called ecchymosis. When the skin of the hemorrhagic lesion is obviously bulged, it is called hematoma. It can be seen in cases of severe bleeding. The beam-arm test, also known as the capillary fragility test, can be used for the suspected case examination. The examination method is to draw a 4cm under the elbow of the forearm. A circle with a diameter of 5cm, carefully observe whether there is a bleeding point in the circle skin. If the bleeding point is found, mark it with an ink pen, and then use the cuff of the sphygmomanometer to bundle the upper arm of the side, first measure the blood pressure, and then keep it at the systolic pressure. After maintaining the pressure for 8 minutes, the pressure is released. After the skin color returns to normal (about 2 minutes), calculate the number of skin bleeding points in the circle, and subtract the number of original bleeding points. If the difference between the two is greater than 10 is positive, the beam arm test of dengue patients is often positive, because the beam arm test may cause the possibility of ecchymosis in the test forearm of patients with severe bleeding tendency, therefore, this test should not be performed too much.

(4) Others: About 1/4 of the cases have mild hepatomegaly, and some cases may have jaundice, but the spleen is rare.

2, light dengue fever

Symptoms and signs are milder than typical dengue fever, with lower fever, less common body pain, less rash or no rash, no bleeding tendency, but superficial lymph nodes are often swollen, the course of disease is often shorter than 5 days, and mild cases during epidemics More, because its clinical manifestations are similar to influenza and acute upper respiratory tract inflammation, the symptoms are milder, so it is easier to be ignored and missed.

3. Heavy dengue fever

Early clinical manifestations resembled typical dengue fever, but after 3 to 5 days of fever, the condition suddenly aggravated, manifested as meningoencephalitis, severe headache, vomiting, convulsions, arrogance, coma, convulsions, excessive sweating, sudden drop in blood pressure, neck stiffness, and pupil dilation Etc. This type of illness is dangerous and progresses rapidly and can die from central respiratory failure within 24 hours.

Dengue check

General routine inspection

1. Peripheral blood: The total number of white blood cells in patients with dengue fever is reduced at the onset of the disease, especially to the rash period. The percentage of neutrophils is also reduced, and there is a clear left shift phenomenon. There are abnormal lymphocytes. The blood of the week returned to normal. The total number of white blood cells in patients with dengue hemorrhagic fever is normal or increased. The latter is found in severe cases and secondary infections, generally above 10,000/mm3, with thrombocytopenia, and the lowest is less than 10,000/mm3.

2, urine routine: there may be a small amount of protein, red blood cells, white blood cells, and sometimes tube type.

Virus isolation

The blood of the early patients was inoculated into Aedes albopictus cell line (C6/36), and the virus was isolated and identified by type-specific neutralization test or hemagglutination inhibition test.

Serum immunological examination

Take double serum for complement fixation test, neutralization test or hemagglutination inhibition test, the hemagglutination inhibition test is more sensitive, and the complement binding test is the most specific, and the recovery period single specimen complement antibody binding antibody titer is reached. More than 1:32 has diagnostic significance, and the double serum titer is more than 4 times higher than can be confirmed.

other

In cases of dengue hemorrhagic fever, blood concentration, clotting time, serum aspartate aminotransferase, prolonged prothrombin time, electrolyte imbalance, decreased albumin, metabolic acidosis, etc. Decreased, fibrinogen decreased, fibrinogen degradation products were mild to moderately increased, and more than a few cases of shock had DIC manifestations.

Dengue diagnosis

Diagnose based on

1. Epidemiological data: Living in dengue fever epidemic areas or 15 days before onset, I have been to dengue fever epidemic areas. The disease occurred in the epidemic season. There were history of worm bites 3 to 15 days before the onset, especially when somewhere When there are a large number of cases of high fever in a short period of time, the possibility of this disease should be considered.

2, clinical features: sudden onset, chills, fever, with systemic pain, obvious fatigue, nausea, vomiting, rash, subcutaneous hemorrhage, superficial lymphadenopathy, beam arm test positive.

3, laboratory examination: if the patient only meets the epidemiological data and clinical manifestations of dengue diagnosis, and no basis for laboratory pathogen-specific examination, it can only be used as a suspected case, if the patient is on the basis of "suspected cases" Furthermore, anti-dengue virus IgG antibody positive in serum can be used as a clinical diagnosis case. If the patient has epidemiological data and clinical manifestations in accordance with the diagnosis of dengue fever, plus anti-dengue virus IgM antibody positive in serum, or double Serum, recovery-specific IgG antibody titers increased 4 times or more than the acute phase, or dengue virus was isolated from serum, which can be diagnosed and become a confirmed case.

Differential diagnosis

1, influenza: nasal congestion, runny nose, sore throat, cough and other symptoms of upper respiratory tract inflammation is more obvious, rash is rare, no skin defects, freckle.

2, measles: cough, runny, tears, eye combined membrane congestion, photophobia, and sore throat, general malaise is common, in the 2nd to 3rd day of the disease, more than 90% of patients have oral Coriolis spots in the mouth, rash is spotted The pimples, first seen in the hair behind the ear, gradually spread to the forehead, face, neck, top to bottom to the chest, abdomen, back and limbs, 2 to 3 days throughout the body, and finally found in the palms and soles.

3, scarlet fever: acute pharyngitis is more obvious, manifested as sore throat, swallowing pain, local congestion and purulent secretions, submandibular and cervical lymph nodes, tenderness, fever after 24h began to rash, starting from behind the ear , neck and upper chest, and then quickly vine and body, rash is diffuse congestive needle-sized papules, fading, accompanied by itching, facial congestion and congestion around the nose and mouth is not obvious, forming a pale perioral ring, throat swab The subculture may have a group A -hemolytic streptococcus growth.

4, epidemic hemorrhagic fever: also known as renal syndrome hemorrhagic fever, patients mainly manifested as fever, symptoms of poisoning, congestion, hemorrhage, shock, oliguria, high blood volume syndrome, fever, bleeding, shock and oliguria appear in turn Commonly, shock often occurs during fever, blood white blood cell count is increased, atypical lymphocytes often exceed 10%, thrombocytopenia, a large amount of protein and membranes appear in the urine, and IgG against epidemic hemorrhagic fever virus can be detected in serum. IgM antibody.

5, leptospirosis: history of contact with water before the disease, acute fever, conjunctival hyperemia, subconjunctival hemorrhage, gastrocnemius pain, inguinal lymphadenopathy, the patient's gastrocnemius pain is more significant when walking, the gastrocnemius tenderness is more obvious during physical examination, IgG, IgM antibodies against Leptospira can be detected in serum.

6, tsutsugamushi disease: before the onset of work or sitting in the bush grass, can be found in the enlarged, tender lymph nodes near the characteristic eschar or ulcer, serum Proteus agglutination test (external - Fiji reaction) check, OXK agglutination antibody The titer of 1:160 or above is diagnostic. The blood is inoculated into the abdominal cavity of the mouse, and the rickettsia can be isolated after 7-10 days of feeding.

7, sepsis: often have primary infections, such as traumatic purulent lesions, pneumonia, enteritis, etc., may appear migratory infections, such as lung abscess, liver abscess, brain abscess, etc., blood leukocytes and neutrophils significantly increased In blood culture or infective aspirate culture, there may be pathogen growth. If the blood culture has the same bacterial growth as the suction culture of the infected lesion, it is more clear diagnostic significance.

8, typhoid fever: sustained fever for more than 1 week, with symptoms of systemic poisoning, such as apathy, lack of appetite, abdominal distension, constipation, relatively slow pulse, liver, splenomegaly, right lower abdomen tenderness, etc., the second week of the disease can be on the chest and abdomen skin Found that the color is reddish, the diameter is 2 ~ 5mm, the pressure fades, the number is often less than 10 rose rash, the peripheral blood leukocyte count decreases, the lymphocyte ratio increases, the eosinophils decrease or disappear, the fat response (typhoid fever The "O" antibody titer in the bacillus serum agglutination reaction may be above 1:80, and the "H" antibody titer may be above 1:160. The blood and bone marrow culture may have typhoid bacillus growth.

9, malaria: intermittent episodes of chills, high fever, a lot of sweating, anemia and splenomegaly, each episode lasts for 4 to 8 hours, the interval of intermittent episodes has a certain regularity, vivax malaria, ovarian malaria is every other day Once, the three-day malaria was attacked every 2 days. The thick blood and thin smear were examined by microscopic oil spectroscopy after Giemsa staining. It was found that the malaria parasite had a clear diagnostic significance.

10, epidemic encephalitis: high fever, headache, vomiting, disturbance of consciousness, convulsions, pathological reflex signs and meningeal irritation positive, blood leukocytes and neutrophils increased significantly, cerebrospinal fluid cell number increased slightly, pressure and protein increased , sugar and chloride normal, serum immunological examination, specific IgM antibody positive has a clear diagnostic significance.

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