Yellow fever: diagnosis

Indications for consultation of other specialists

In some cases, consultation of a neurologist, cardiologist, and surgeon is necessary.

Indications for hospitalization

Indication depends on the medical rules of different countries.

Clinical diagnosis of yellow fever

Diagnosis of yellow fever in most patients is based on the characteristic symptoms of the disease (a typical saddle-shaped temperature curve, severe hemorrhagic diathesis symptoms, kidney damage, jaundice, enlarged liver and spleen, bradycardia, etc.). In this case, the presence of an endemic focus is taken into account; species composition and abundance, attack activity on humans and other characteristics of vectors; as well as laboratory data (leukopenia, neutropenia, lymphocytopenia, significant albuminuria, hematuria, bilirubinemnia, azotemia, a significant increase in aminotransferase activity).

[1], [2], [3], [4], [5], [6], [7], [8], [9],

Specific and nonspecific laboratory diagnostics of yellow fever

The specific diagnosis of yellow fever is based on the establishment of the complement fixation reaction, RPHA, nonspecific RIF, ELISA, and RTGA in paired sera. The result is considered positive with a fourfold increase in the antibody titer. Recommended virological tests: virus RN and virus isolation. The causative agent is isolated from the patient's blood during the first 3 days of the disease by infecting white mice and monkeys, so for fatal outcomes, the collection of sectional material should be carried out as quickly as possible. Usually, a liver sample is taken from which a suspension is prepared and, after treatment with antibiotics, is immediately injected into the brain or monkeys by mice parenterally. If the mice did not have clinical manifestations of the disease, a blind passage is carried out. With the appearance of signs of the disease, several (3-5) additional passages are carried out in mice, after which an antigen is prepared from the brain substance of the infected animals by means of which the identification of the isolated virus in serological reactions (RTGA, RSK) or PH with a specific antiserum is carried out.

In case of lethal outcome, liver tissue is examined, where foci of submissive or massive necrosis of the hepatic lobules and Kaunsilman's acidophilus bodies are detected.

Algorithm for diagnosing yellow fever

• Stage 1. An epidemiological anamnesis is carried out (the patient was in the tropical zones of South America or Africa). (With positive results, the study continues.)
• Stage 2. Study the course of the disease. The onset is acute, intoxication and high fever are expressed. (With positive results, the study continues.)
• Stage 3. Identify abdominal pain, vomiting, nausea, loose stool, headache, myalgia, agitation. (With positive results, the study continues.)
• Stage 4. Identify the presence of hemorrhagic syndrome (nasal bleeding, bleeding gums, an admixture of blood in the vomit), subic- ticity or icteric skin and sclera. (With positive results, the study continues.)
• Step 5. Diagnose the enlargement of the liver and spleen, puffiness of the face (with a purplish-bluish tinge). End of the study.

Diagnosis: yellow fever (serological diagnosis should be performed to exclude other hemorrhagic fevers).

[10], [11], [12],

Differential diagnosis of yellow fever

Differential diagnosis of yellow fever is carried out with tropical malaria, icteric form of leptospirosis, viral hepatitis, meningococcemia, and hemorrhagic fever Lassa, Marburg and Ebola and HFRS.

Differential diagnosis of yellow fever

Disease	Similarities	Differences
Leptospirosis	Acute onset of the disease, high fever, headaches myalgia, hemorrhagic manifestations, oliguria. Conjunctivitis scleritis, jaundice is possible	Yellow fever is not characterized by pain in the calf muscles: myalgia is less pronounced. In the blood, leukopenia is detected. Kidney damage often occurs, albuminuria develops photophobia, lacrimation. Less commonly, meningeal symptoms occur, there are no changes in the cerebrospinal fluid
Malaria	Headaches, a rise in temperature to high values, a sensation of aches in the body, an increase in the liver and spleen. Jaundice, oliguria	With malaria, there is no increase in peripheral lymph nodes, but in contrast to yellow fever sweating, pallor, the correct cyclic nature of temperature changes. Hemorrhagic syndrome is less common in malaria and it is less pronounced
HFRS	Acute onset of the disease, high fever, muscle and headaches, hemorrhagic syndrome. Scleritis oliguria	Yellow fever is characterized by: saddle-shaped temperature curve, marked signs of hemorrhagic diathesis, kidney damage, jaundice. Enlargement of the liver and spleen. With HFRS in the first day of the course of the disease, severe dryness and thirst are revealed, and oliguria develops against a background of subfebrile or normal temperature from the second week of the course

[13], [14], [15],