Overview
Acute hemorrhagic infectious disease transmitted by the bite of Aedes aegypti mosquitoes may have high fever, nausea, vomiting, yellow skin, skin hemorrhages, etc. No specific antiviral drugs, symptomatic supportive treatment, including antipyretic, hepatoprotection, etc., mostly prognosis is better, the death rate of severe cases is high.
Definition
Yellow fever is an acute hemorrhagic infectious disease transmitted by the bite of the Aedes aegypti mosquito.
Yellow fever mainly involves internal organs, such as the liver, kidneys and heart, and may manifest as high fever, nausea, vomiting, jaundice, skin petechiae, and foamy urine.
Types
Yellow fever can be categorized into jungle type and urban type according to the characteristics of epidemic transmission and geographical conditions.
The jungle type mainly occurs in tropical rainforests.
The urban type mainly occurs in densely populated cities.
Incidence
The disease is mainly prevalent in Africa and South America’s tropical and subtropical regions, the incidence of March to April rainy season is higher, because of high humidity, high temperature is conducive to mosquito breeding and virus reproduction in the mosquito body.
During the yellow fever epidemic in the 1980s, the case fatality rate was high, and with the coverage of the vaccine, the outbreak was brought under control. However, in 2016-2017, outbreaks occurred again in Africa and South America, with 8,262 cases reported in Angola and the Republic of Congo; 403 cases were reported in Brazil, including 84 deaths (including suspected cases) [2-3].
Questions you may be concerned about
What is yellow fever?
Yellow fever is caused by yellow fever virus infection, manifested by fever, jaundice and other symptoms, this product is mainly symptomatic treatment with antipyretic and analgesic, liver preservation.
Yellow fever is an acute infectious disease, caused by yellow fever virus infection, transmitted through mosquito bites. It is mainly characterized by chills, high fever, headache, vomiting, jaundice, proteinuria, bleeding gums, nosebleeds, skin petechiae and other symptoms. Patients can be complicated by hemorrhage, shock, heart damage, uremia, and multiple organ hypofunction.
There is no specific antiviral drug for the treatment of yellow fever, which is mainly based on symptomatic treatments such as acetaminophen and other antipyretic and analgesic drugs, hepatoprotective treatment, and supplementation of vitamin K to promote coagulation.
The diagnosis of the disease should be followed by the doctor’s advice and active treatment, so as to avoid delaying the disease.
Causes
Causes
Yellow fever is caused by yellow fever virus infection, the basic conditions leading to the epidemic are the following three aspects.
Source of infection
The main source of infection for the jungle type is monkeys and other primates, and for the urban type, it is patients and people with latent infections.
Route of transmission
The jungle type occurs in tropical rainforests and spreads by primates → Aedes aegypti and Aedes aegypti → humans, with monkeys as the main source of infection.
The urban type occurs in densely populated cities, where travelers or workers in the jungle are infected by mosquito bites, and return to urban areas to spread the disease to others through mosquito bites, forming a human → Aedes aegypti → human mode of transmission [1,4].
Susceptible population
The population is universally susceptible and acquires lasting immunity after infection.
The jungle type is more common in adult males, while the urban type is more common in children [1].
Pathogenesis
The pathogenesis of yellow fever is not fully understood, and viral invasion and replication is now considered one of the more likely mechanisms. Yellow fever virus is visceral and can form viremia after invading the human body, mainly invading internal organs such as liver, kidney, heart, etc., causing corresponding symptoms.
After invading the human body, the yellow fever virus spreads rapidly to the local lymph nodes and reproduces continuously in them, and then enters the blood circulation and forms viremia after 3 to 4 days, and the virus then invades the liver, spleen, kidney, lymph nodes, heart, bone marrow, and rhabdomyosarcoma.
The virus often invades the liver and causes severe lesions, resulting in yellowing of the skin and sclera, vomiting of blood, bleeding gums, hypoglycemia, etc. Damage to the kidneys may result in renal decompensation and uremia, which may be manifested as foamy urine, oliguria, etc. Damage to the myocardium may result in slowing down of the heart rate and cardiac failure.
Symptoms
Main Symptoms
The incubation period, that is, the time from the invasion of the virus into the body to the appearance of symptoms, is about 3 to 6 days, or up to 10 days [5].
Most are asymptomatic, or mildly infected, with widely varying clinical manifestations, and the condition can range from mildly self-limiting to lethal infection, with the typical clinical course being categorized into the following 4 phases.
Infection stage
Lasting for about 3 days, it manifests as high fever, chills, headache, muscle pain, obvious weakness, loss of appetite, nausea, vomiting, diarrhea, vomiting blood or black stools, as well as conjunctival congestion, scarlet face and neck, and dry skin.
Body temperature is often 40°C and above, and initially the heart rate rises with increasing body temperature, with subsequent slower heart rate.
Remission period
Often begins on the 4th day of illness, body temperature decreases or subsides completely, headache, nausea and other symptoms are relieved, lasting a few hours to 1 day.
Toxic phase
Symptoms reappear and become more severe, manifesting as multi-organ damage to the liver, kidneys, heart and bleeding.
Symptoms may include yellowing of the skin and sclera, foamy urine, oliguria, bradycardia, lowered blood pressure, etc. Bleeding manifests itself in the form of bleeding gums, vomiting of blood, reddish urine, and neurological symptoms such as irritability, delirium, and coma in severe cases.
It lasts from 3 to 2 weeks, and most deaths occur during this period.
Recovery period
Survivors’ body temperature may gradually drop to normal, symptoms disappear, but weakness may persist for 1 to 2 weeks or longer, and surviving cases usually have no sequelae.
Complications
Intestinal hemorrhage, shock, disseminated intravascular coagulation (DIC) and other serious complications can occur in severe cases of yellow fever.
Intestinal hemorrhage
Manifested as abdominal pain, diarrhea, black stool, blood in stool, etc.
Heart failure
Shortness of breath after activity, dyspnea, coughing up pink foamy sputum, etc.
Shock
Manifested by decreased blood pressure, increased heart rate, clammy skin, impaired consciousness, etc.
Disseminated intravascular coagulation
Bleeding spots and petechiae on the skin, dyspnea, oliguria, impaired consciousness, etc. [1-6].
Medical treatment
Department of Medicine
Department of Infection Medicine
If symptoms such as fever, headache, nausea, vomiting, yellowing of skin and sclera occur after traveling or being bitten by mosquitoes in an infected area, consult the Department of Infectious Diseases.
Fever Clinic
You can also consult the Fever Clinic if you experience any of the above symptoms.
Preparation
Information on how to get to the clinic: registration, preparation of documents, common problems
Tips for medical treatment
If you have a high fever, you may need to apply physical measures to lower the temperature, such as placing a warm towel on the forehead and wiping the armpits with lukewarm water, before seeking medical treatment.
You may need to have a full body checkup or chest CT examination, so you should wear loose clothing.
Preparation List
Symptom list
Pay particular attention to the time of onset of symptoms, special manifestations, etc.
Are there any symptoms such as fever, chills, headache, muscle aches, loss of appetite, etc.?
Are there any symptoms such as nausea, vomiting, diarrhea, yellowing of the skin and sclera eyes?
Any symptoms such as foamy urine, oliguria, etc.?
List of medical history
Any recent mosquito bites?
Any recent history of jungle travel?
Any recent travel to Africa, Central or South America, or elsewhere?
Checklist
Test results from the last 1 week that can be brought to the doctor’s office
Laboratory tests: blood tests, liver and kidney function, coagulation function, etc.
Imaging tests: abdominal ultrasound, etc.
Medication list
Medication used in the last 1 week, if available, bring along the box or package for medical consultation
Antipyretic and analgesic: ibuprofen, acetaminophen, etc.
Diagnosis
Diagnosis based on
medical history
Patients with this disease may have the following epidemiologic history.
History of travel to places such as Africa and South America.
A history of jungle travel.
History of mosquito bites.
Clinical manifestations
Most of the infections are asymptomatic or mildly symptomatic and may include fever, chills, muscle aches, loss of appetite, nausea, and vomiting.
In severe cases, there may be obvious yellowing of the skin, oliguria, bradycardia, decreased blood pressure, etc. Severe hemorrhagic symptoms such as vomiting of blood, black stools, reddish urine, and even irritability, delirium and coma.
Laboratory Tests
Blood routine
The total number of white blood cells is normal or increased, the number of neutrophils is decreased, and the platelet count is normal or decreased.
Biochemical examination
There may be elevation of alanine aminotransferase (ALT) and aliquot transaminase (AST), elevation of serum total bilirubin and conjugated bilirubin; prolongation of coagulation time and prothrombin time; elevation of serum urea nitrogen and creatinine.
Fecal Occult Blood Test
Fecal occult blood test is often positive, suggesting the possibility of gastrointestinal bleeding.
Pathogenetic examination
Nucleic acid test: application of polymerase chain reaction (PCR) examination can detect blood, urine and other body fluid specimens of yellow fever virus RNA, which can be used for early diagnosis of the disease [5].
Virus isolation: blood from patients or tissue specimens from dead cases within 5 days of onset can be used for virus isolation.
Antigen detection: use immunohistochemical methods to detect viral antigen in tissue specimens; use ELISA methods to detect viral antigen in blood and other specimens.
Immunological tests
Enzyme-linked immunosorbent assay (ELISA) can detect yellow fever virus-specific IgM and IgG antibodies, and a 4-fold or greater increase in antibody potency in both acute and recovery phases of the serum can help to determine the diagnosis [1,4-6].
Diagnostic criteria
Suspected cases
Epidemiologic history with corresponding clinical manifestations.
Epidemiological history: history of living or traveling in a yellow fever endemic area within 14 days prior to the onset of illness.
Clinical manifestations: fever, jaundice, hepatic and renal impairment, or hemorrhage that are difficult to explain by other causes.
Clinical diagnosis of cases
Suspected case with positive IgM antibody test for yellow fever virus.
Confirmed cases
A suspected case or a clinically diagnosed case that meets one of the following conditions after laboratory testing:
Positive nucleic acid test for yellow fever virus.
Isolation of yellow fever virus.
The serum yellow fever virus antibody titer in the recovery period is 4 times or more higher than that in the acute period, and other viral infections such as dengue fever and Zika virus are excluded at the same time.
Differential diagnosis
Yellow fever should be differentiated from malaria, dengue fever, and renal syndrome hemorrhage.
Malaria
Similarities: both often occur in the tropics and subtropics, with a history of mosquito bites.
Differences: malaria is clinically characterized by periodic episodes of fever, chills, and profuse sweating, usually without hemorrhage and urinary protein, and can be differentiated by pathogenetic testing.
Dengue fever
Similarity: Both often occur in the tropics and subtropics, with a history of mosquito bites.
Differences: dengue fever is mainly characterized by fever, profuse sweating and rash, serologic testing can be differentiated.
Renal syndrome hemorrhagic fever
Similarity: Both have fever, headache, bleeding, and foamy urine.
Differences: renal syndrome hemorrhagic fever occurs in the fall harvesting season, there is a history of rodent exposure, farmers are the high incidence of the population, renal syndrome hemorrhagic fever antibody IgM positivity can help to differentiate [1].
Treatment
Treatment objective: to relieve symptoms, prevent and control severe disease, and reduce the morbidity and mortality rate.
Treatment principle: there is no specific antiviral drug in the clinic at present, and general and symptomatic treatment is the mainstay.
General treatment
In the acute stage, bed rest is required until complete recovery, and it is advisable to gradually increase the activity level.
Diet should be light, fluid or semi-fluid, frequent vomiting should be fasting, and fluid rehydration can be used at the same time.
Symptomatic treatment
When high fever occurs, physical hypothermia, or application of small doses of ibuprofen, acetaminophen and other antipyretic treatment, should avoid the use of aspirin, so as not to aggravate the bleeding.
When vomiting is obvious, metoclopramide can be injected orally or intramuscularly, and intravenous rehydration can be carried out at the same time to maintain the balance of water, electrolytes and acid-base.
When there is hepatic impairment, bisacodyl, ursodeoxycholic acid and other drugs can be applied to protect the liver.
When there is gum bleeding, skin petechiae, vomiting blood, platelets, plasma and coagulation factors can be supplemented, and blood transfusion can be used if necessary.
In acute renal failure, renal replacement therapy such as hemodialysis can be performed.
Prognosis
Cure
Patients with mild disease can usually recover successfully without significant impact on the body.
Patients with rapid progression of the disease, accompanied by renal failure, severe bleeding, disseminated intravascular coagulation, and shock, are more difficult to cure and have a high case fatality rate.
The case fatality rate of yellow fever is about 2% to 20%, but the case fatality rate of severely ill patients varies according to different races, different ages, etc., and can reach 30% to 50% [1].
Hazards
After infection, fever, malaise, headache, vomiting, diarrhea, vomiting blood and other manifestations can occur, affecting patients’ normal work and life.
In severe cases, liver failure, renal failure, hemorrhage and shock can occur, and other serious manifestations can be life-threatening.
Daily
Daily management
In the acute stage, a light diet, fluid or semi-fluid diet, small and frequent meals, and nutritional supplementation are needed. High protein, high calorie and high vitamin foods can be consumed to ensure energy supply.
Eat more fresh vegetables and fruits and drink more water to replenish vitamins and water.
In the acute stage, bed rest is needed to reduce the amount of activity and physical exertion.
Prevention
Control the source of infection
It is advisable to isolate and treat patients in situ, and at the same time pay attention to preventing mosquito bites.
Implement health quarantine for people from yellow fever infected areas.
Cutting off the means of transmission
Preventing mosquito bites is a basic measure to prevent yellow fever.
Avoid going outside at dusk and dawn when mosquitoes are most active, if possible.
In outdoor areas such as jungles, mosquito repellents such as antitetracycline and oil of lemon eucalyptus can be sprayed on the skin and clothing.
Wear long sleeves, pants and socks to minimize mosquito bites whenever possible.
When spending the night outdoors, it is recommended to stay in tents or local hotels and use both mosquito nets and mosquito coils [8-10].
Protecting susceptible people
Vaccination against yellow fever is an effective measure to prevent infection.
People entering the virus endemic areas in Africa or South America can be vaccinated in advance.
Yellow fever vaccination is not recommended for children under 9 months of age, pregnant women, or immunocompromised individuals.
The vaccine produces long-lasting antibodies that provide lifelong immunity.
In rare cases, severe allergy and respiratory distress can occur after vaccination, which can be life-threatening [6,11-12].