Yellow fever - Diagnosis

Indications for consultation with other specialists

In some cases, consultation with a neurologist, cardiologist, or surgeon is necessary.

Indications for hospitalization

Indications depend on the medical regulations of different countries.

Clinical diagnosis of yellow fever

The diagnosis of yellow fever in most patients is based on the characteristic symptoms of the disease (typical saddle-shaped temperature curve, pronounced symptoms of hemorrhagic diathesis, 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 numbers, activity of attack on humans and other characteristics of carriers; as well as laboratory test data (leukopenia, neutropenia, lymphocytopenia, significant albuminuria, hematuria, bilirubinemia, azotemia, significant increase in aminotransferase activity).

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Specific and non-specific laboratory diagnostics of yellow fever

Specific diagnostics of yellow fever is based on the complement fixation reaction, RPGA, non-specific RIF, ELISA and RTGA in paired sera. The result is considered positive with a fourfold increase in the antibody titer. Recommended virological tests: virus pH and virus isolation. The pathogen is isolated from the patient's blood during the first 3 days of the disease by infecting white mice and monkeys, so in case of fatal outcomes, autopsy material must be collected as quickly as possible. Usually, a liver sample is taken, from which a suspension is prepared and, after treatment with antibiotics, immediately injected into the brain of mice or parenterally into monkeys. If no clinical manifestations of the disease are detected in mice, one blind passage is carried out. When signs of the disease appear in mice, several (3-5) additional passages are carried out, after which an antigen is prepared from the brain matter of infected animals, with the help of which the isolated virus is identified in serological reactions (HI, RSC) or RN with a specific antiserum.

In case of death, liver tissue is examined, where foci of submassive or massive necrosis of the liver lobules and acidophilic Councilman bodies are detected.

Algorithm for diagnosing yellow fever

• Stage 1. An epidemiological anamnesis is conducted (the patient was in the tropical zones of South America or Africa). (If the results are positive, the study is continued.)
• Stage 2. The course of the disease is studied. The onset is acute, intoxication and high fever are pronounced. (If the results are positive, the study is continued.)
• Stage 3. Abdominal pain, vomiting, nausea, loose stools, headache, myalgia, and agitation are detected. (If the results are positive, the study is continued.)
• Stage 4. The presence of hemorrhagic syndrome (nosebleeds, bleeding gums, blood in vomit), subicteric or icteric skin and sclera are identified. (If the results are positive, the study is continued.)
• Stage 5. Diagnose enlarged liver and spleen, puffiness of the face (with a purple-bluish tint). End of the study.

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

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Differential diagnosis of yellow fever

Differential diagnosis of yellow fever is carried out with tropical malaria, icteric form of leptospirosis, viral hepatitis, meningococcemia, as well as with 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, possible jaundice	Yellow fever is not characterized by pain in the calf muscles: myalgia is less pronounced. Leukopenia is detected in the blood. Kidney damage occurs more often, albuminuria, photophobia, and lacrimation develop. Meningeal symptoms occur less often, and there are no changes in the cerebrospinal fluid.
Malaria	Headaches, high fever, body aches, enlarged liver and spleen. Jaundice, oliguria	With malaria there is no enlargement of the peripheral lymph nodes, but unlike yellow fever there is sweating, pallor, and a regular cyclical nature of temperature changes. Hemorrhagic syndrome with malaria is detected less often and is less pronounced.
HFRS	Acute onset of the disease, high fever, muscle and headaches, hemorrhagic syndrome. scleritis oliguria	Yellow fever is characterized by: a saddle-shaped temperature curve, pronounced signs of hemorrhagic diathesis, kidney damage, jaundice. enlarged liver and spleen. With HFRS, severe dryness and thirst are detected in the first day of the disease, and oliguria develops against the background of subfebrile or normal temperature from the second week of the disease.

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