Yellow fever is an acute infectious disease caused by yellow fever virus and transmitted by mosquito bites. The main clinical manifestations are fever, jaundice, and hemorrhage. The late stage of the disease can cause extensive tissue lesions, liver and kidney necrosis, myocardial fatty change, skin, gastrointestinal mucosal bleeding, and severe cases can be fatal.
Yellow fever virus is a single-stranded positive-sense RNA virus belonging to the Flavivirid family. The resistance of yellow fever virus is weak, it is not resistant to acid and heat. It can be inactivated at 60 degrees for 30 minutes, and can be inactivated by 70% ethanol, 0.5% sodium hypochlorite, fat solvent, peracetic acid and other disinfectants and ultraviolet radiation.
Epidemiology
It is mainly prevalent in the tropical regions of Central and South America and Africa, where the disease can occur throughout the year, and the incidence is high in the season when the mosquito vector is active.
The sources of urban infection are patients and latent infections, which circulate in a "human-Aedes aegypti-human" manner. The main source of infection of the jungle type is monkeys and other non-human primates, which circulate in a "monkey-Aedes africanus or haemophilus, etc.-monkey" manner. The disease is mainly transmitted by mosquito bites, and people are generally susceptible to yellow fever virus.
Disease type
According to the mode of transmission, yellow fever is mainly divided into urban type and jungle type:
The main sources of infection for the urban type are patients and latent infections, and the main carrier is Aedes aegypti.
The main source of infection of the jungle type is monkeys and other non-human primates, and the vector species of mosquitoes are relatively complex, including Aedes africanus, Aedes simpson, Haemotropus, and Anopheles.
Basic cause
The cause of yellow fever is well established. Mosquitoes carrying the yellow fever virus can cause the disease by biting susceptible individuals. The virus can replicate at the bite site, spread to other organs and tissues through lymph and blood, and multiply in them, and then release into the blood, causing viremia. It mainly invades organs and tissues such as liver, spleen, heart, bone marrow and striated muscle.
Predisposing factors
Activities in yellow fever-affected areas without vaccination are predisposing factors for this disease.
Symptom
Symptoms mainly include fever, general malaise, myalgia, gastrointestinal symptoms and liver damage. In addition to the liver, the disease can also affect the kidneys, heart and nervous system, showing corresponding symptoms.
Typical symptoms
The incubation period of yellow fever is usually 3 to 6 days, and can be as long as 10 days, and corresponding symptoms will appear after the incubation period. Most people who are infected with yellow fever virus are asymptomatic or have mild symptoms. The clinical course of a typical case can be divided into the following four phases, each with different manifestations.
Infectious period
This period is the viremia period, which lasts for 3 to 5 days, manifested by chills, fever (up to 39 degrees to 41 degrees), headache, dizziness, photophobia, pain in the lumbosacral region and lower limbs (especially the knee joint), muscular Pain, anorexia, nausea, vomiting, irritability, irritability, general malaise, etc., but the symptoms are not specific. Physical examination may reveal relative bradycardia, hyperemia of the skin, conjunctiva, and gums, characteristic tongue coating changes (red tip with white coating), hepatomegaly, and epigastric tenderness.
Remission period
After 3 to 5 days of fever, the patient enters the remission period, and the symptoms in this period are less than those in the infection period.
Toxic period (liver and kidney damage period)
This period is characterized by re-exacerbation of the disease and multiple organ dysfunction, often involving the liver, kidneys and blood system.
Recovery period
It can last for 2 to 4 weeks, the symptoms will gradually disappear, and the organ functions will gradually return to normal, but the fatigue symptoms can last for several weeks. Jaundice and elevated transaminases can persist for several months.
Accompanying symptoms
The poisoning period can involve the liver, kidneys and even the heart and nervous system.
The clinical manifestations are body temperature rising again, jaundice gradually aggravating, frequent vomiting, epigastric pain; multi-site bleeding may also occur, such as skin petechiae, ecchymosis, epistaxis, mucous membrane bleeding, and even cavity bleeding and shock; abnormal renal function may Proteinuria, hematuria, decreased urine output, or even anuria; heart manifestations may have ST-T changes in electrocardiogram, and a few may have acute heart enlargement; nervous system manifestations include agitation, delirium, and coma.
Seek medical attention
If you have no obvious symptoms after being bitten by mosquitoes in areas where yellow fever is endemic, you can observe at home. If symptoms of fever occur, seek medical attention as soon as possible. In case of jaundice, skin bleeding points, oliguria, arrhythmia, etc., seek emergency medical attention.
Medical department
Department of Infectious Diseases, Fever Clinic.
Diagnosis process
When seeing a doctor, the doctor may ask the following questions to get a preliminary understanding of the condition, and the patient can prepare answers in advance:
How long have you had a fever? What is the maximum temperature?
Are there any symptoms of yellow skin?
Are there any symptoms of skin bleeding?
Ever been to Africa, Central and South America, or anywhere else?
Have you ever been bitten by a mosquito recently?
Doctors will make a diagnosis based on the following:
Suspected cases need to meet the following characteristics
Within 14 days before the onset of illness, there was experience of living or traveling in yellow fever-endemic areas, and clinical manifestations such as fever, jaundice, liver and kidney dysfunction, or hemorrhage that could not be explained by other reasons.
Clinically diagnosed cases need to meet the following characteristics
Suspected case with positive yellow fever virus IgM antibody test.
Confirmed cases need to meet the following characteristics:
Suspected cases or clinically diagnosed cases, and the yellow fever virus nucleic acid test is positive, or the yellow fever virus is isolated, or the serum yellow fever virus antibody titer in the convalescent stage is 4 times higher than that in the acute stage, and dengue fever and Zika virus are excluded at the same time and other common flavivirus infections.
Physical examination
Skin, conjunctiva, mucous membrane: observe whether the skin has jaundice, blood stasis and ecchymosis, and whether the conjunctiva and gums are congested.
Heart: Percuss the heart for enlargement.
Abdomen: Tenderness and rebound tenderness on palpation.
Nervous system: Observe whether the mind is clear, whether there is restlessness, delirium, or coma.
lab test
Blood test
Peripheral blood leukopenia, decreased proportion of neutrophils, decreased platelets.
Routine urine test
Proteinuria with granular casts and red blood cells.
Liver function test
Serum transaminases rise earlier than bilirubin, aspartate aminotransferase (AST) rises more than alanine aminotransferase (ALT), serum bilirubin can also rise significantly, blood ammonia can also be seen High, low blood sugar, etc.
Coagulation test
The prothrombin time prolongs, the activity of prothrombin decreases, and the coagulation factors (Ⅱ, Ⅴ, Ⅶ, Ⅸ and Ⅹ) decrease.
kidney function test
Increased blood creatinine levels.
Myocardial injury markers examination
Serum troponin can be significantly increased when myocardial damage.
Other biochemical tests
May have myoglobin, blood amylase, lipase, urine amylase can also be significantly increased.
Immunological examination
There may be IgM antibody, yellow fever virus antigen, and serum-specific IgG antibody positive.
Pathological examination
Yellow fever virus RNA can be detected in blood, urine, and other body fluid samples.
Typical influenza
The main symptoms are fever and systemic poisoning. High fever of 39 to 40 degrees, lasting 4 to 7 days; accompanied by chills or chills, headache, arthralgia, myalgia, general malaise and anorexia. The diagnosis can be confirmed when the influenza virus is isolated from the nasopharyngeal secretions of the patient or the serum antibody in the convalescent phase is ≥4 times higher than that in the acute phase.
Typhoid fever
Before the onset of typhoid fever, there is often a history of eating unclean food. The onset is slow, body temperature rises gradually, relatively slow pulse, indifferent expression, abdominal distension, constipation, right lower quadrant tenderness, and roseola are common. The test can find that the total number of white blood cells in the blood has decreased, and the eosinophils have decreased or disappeared. Vita reaction can be positive, and blood and bone marrow cultures can have Salmonella typhi growth.
Typhus
It mostly occurs in winter and spring, with a history of being bitten by lice, acute onset, high fever often accompanied by chills, rapid pulse, and early rash (on the 5th to 6th day), which is extensive and dense, and is often hemorrhagic. Regression, normal or slightly higher white blood cell count, and a positive Waifield reaction.
Cases of fever with jaundice
Patients with fever and jaundice should be differentiated from jaundice-hemorrhagic leptospirosis and liver damage caused by various causes.
Jateric hemorrhagic leptospirosis
It occurs frequently in summer and autumn, and most patients have a history of contact with infected water. Clinically, in addition to fever, there may be gastrocnemius muscle tenderness, inguinal lymph node enlargement, tenderness, liver function damage, progressive jaundice, bleeding and kidney damage. Antibodies are detected by a coagulation test. If the antibody titer increases by more than 1:400, the disease can be considered; further blood cultures are used to find pathogens, and the diagnosis can be confirmed.
Cases of fever with bleeding
Fever with hemorrhagic disease should be differentiated from dengue fever and hemorrhagic fever with renal syndrome.
Dengue
An acute infectious disease caused by dengue virus characterized by sudden onset of fever, relative bradycardia and headache, severe joint and muscle pain, swollen lymph nodes and rash. Dengue virus antigen or viral nucleic acid is detected in the serum, or dengue virus is isolated, or the serum specific IgG antibody titer in the recovery period increases by more than 4 times, and the diagnosis can be confirmed.
Hemorrhagic fever with renal syndrome
Also known as epidemic hemorrhagic fever, it is caused by Hantaan virus and is a natural foci disease with rodents as the main source of infection. The main clinical manifestations are fever, shock, mucous membrane congestion, hemorrhage, visceral hemorrhage and kidney damage. Performance. Widely popular in countries such as Asia and Europe, my country is a high-incidence area. The detection of viral antigens and specific IgM antibodies in patients can confirm the diagnosis.
Treat
There is no specific antiviral treatment for the pathogen. Treatment is mainly symptomatic and supportive, and prevention and treatment of complications.
General treatment
Bed rest until complete recovery, the amount of activity should be gradually increased to prevent sudden changes in the cardiovascular system.
The diet should be liquid or semi-liquid, and fasting occurs when frequent vomiting occurs.
Appropriate rehydration, vitamin B, vitamin C, vitamin K and blood transfusion or plasma to maintain water, electrolyte and acid-base balance.
Strengthen skin care and oral care to keep the stool unobstructed. Monitor the patient's vital signs.
Medical treatement
Due to large individual differences, there is no absolute best, fastest, or most effective medication. Except for commonly used over-the-counter drugs, you should choose the most appropriate drug based on your personal situation under the guidance of a doctor.
There is no specific antiviral drug treatment for this disease, and the main treatment is symptomatic and supportive.
Antipyretic and Pain Relief Treatment
When the fever is high, reduce the temperature physically, and if necessary, give small doses of antipyretic and analgesic agents, such as acetaminophen. Because aspirin and indomethacin (indomethacin) can induce or aggravate bleeding, they should be avoided.
Liver protection treatment
When liver function is damaged, hepatoprotective, enzyme-lowering, and jaundice-reducing treatments are given. Vitamin K is added to promote the synthesis of coagulation factors. In severe bleeding, coagulation factors, platelets, fresh plasma, etc. are supplemented, and red blood cells are transfused when necessary.
Upper gastrointestinal bleeding treatment
Proton pump inhibitors and thrombin can be used for upper gastrointestinal bleeding.
Cerebral Edema Treatment
When cerebral edema occurs, osmotic diuretics (3% hypertonic saline or 20% mannitol) are used for dehydration therapy.
Other treatments
Renal replacement therapy: In case of acute kidney injury, renal replacement therapy can be given if necessary.
Prognosis
Most people infected with yellow fever virus are asymptomatic or mildly infected. They can be cured after treatment, but if the disease is not under control and enters the poisoning stage, there will be a higher mortality rate.
Complication
Liver and kidney failure, heart damage and hemorrhagic shock may occur during the poisoning period.
Liver failure
Manifested as aggravated jaundice, elevated transaminases, and serum bilirubin.
Kidney failure
Manifested as proteinuria, hematuria, decreased urine output, or even anuria, elevated serum creatinine.
Heart damage
Electrocardiogram shows ST-T changes, a small number of acute heart enlargement, blood troponin significantly increased, severe cases can cause arrhythmia and death.
Hemorrhagic shock
Manifested as skin petechiae, ecchymosis, epistaxis, mucous membrane bleeding, and even visceral hemorrhage, followed by shock.
Daily
High heat can easily cause dehydration, so it is especially important to pay attention to fluids in your diet. Before recovery, you should pay close attention to the changes in the patient's condition, and seek medical treatment in time if necessary.
Home care
Pay attention to mosquito repellent, you can apply mosquito repellants such as essential oils on the neck, cuffs and other exposed skin to reduce mosquito bites;
Wash hands before and after touching patients. The windows are opened regularly every day for ventilation, and the room is disinfected to keep the room clean and hygienic.
Daily life management
Patients with chills and high fever can easily cause water loss in the body. In order to maintain electrolyte balance, we must carefully guide diet. Encourage patients to supplement high-vitamin, high-calorie, high-protein, light and digestible liquid or semi-liquid food, eat small meals frequently to ensure sufficient heat energy supply, eat more fresh vegetables and fruits, and drink plenty of water.
Daily Condition Monitoring
Closely observe the patient's body temperature, heart rate, respiration, blood pressure and other vital signs, pay attention to the patient's spirit, consciousness, urine volume, urine color, as well as the color of vomit and stool, observe the color of the skin, and whether there are bleeding spots. In case of high fever, physical cooling should be given, such as head pillow with ice pack, cold towel on the head or warm water bath, etc., and antipyretic drugs should be given if necessary.
Advise the patient to drink plenty of water to replenish water, seek medical attention if necessary, and provide intravenous rehydration.
Keep warm when you are shivering or sweating profusely, and add a large bath towel on the bed sheet to absorb sweat, and change cotton clothes, bed sheets, and quilts in time. Prepare ECG monitor, oxygen inhalation device, etc. at the bedside, report to the doctor in time if the condition changes, and cooperate with active rescue.
Special considerations
Patients and family members need to understand the source of yellow fever infection, transmission route, clinical characteristics and preventive measures, and understand the importance of mosquito prevention and extermination for this disease.
It is necessary to pay attention to the prevention and control of mosquitoes in daily life, and to take protective measures for oneself when in contact with patients.
Prevention
Control the source of infection
Effective anti-mosquito isolation measures should be taken for suspected, clinically diagnosed and confirmed cases. Implement health quarantine for people from yellow fever epidemic areas.
Cut off the transmission route
Mosquito control is an important prevention and control measure for this disease.
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