Dengue Hemorrhagic Fever

The principal symptoms of dengue are:

  • High fever and at least two of the following:
  • Severe headache
  • Severe eye pain (behind eyes)
  • Joint pain
  • Muscle and/or bone pain
  • Rash
  • Mild bleeding manifestation (e.g., nose or gum bleed, petechiae, or easy bruising)
  • Low white cell count

Generally, younger children and those with their first dengue infection have a milder illness than older children and adults.

Watch for warning signs as temperature declines 3 to 7 days after symptoms began.
Go IMMEDIATELY to an emergency room or the closest health care provider if any of the following warning signs appear:

  • Severe abdominal pain or persistent vomiting
  • Red spots or patches on the skin
  • Bleeding from nose or gums
  • Vomiting blood
  • Black, tarry stools (***, excrement)
  • Drowsiness or irritability
  • Pale, cold, or clammy skin
  • Difficulty breathing

Dengue hemorrhagic fever (DHF) is characterized by a fever that lasts from 2 to 7 days, with general signs and symptoms consistent with dengue fever. When the fever declines, warning signs may develop. This marks the beginning of a 24 to 48 hour period when the smallest blood vessels (capillaries) become excessively permeable (“leaky”), allowing the fluid component to escape from the blood vessels into the peritoneum (causing ascites) and pleural cavity (leading to pleural effusions). This may lead to failure of the circulatory system and shock, and possibly death without prompt, appropriate treatment. In addition, the patient with DHF has a low platelet count and hemorrhagic manifestations, tendency to bruise easily or have other types of skin hemorrhages, bleeding nose or gums, and possibly internal bleeding. 


There is no specific medication for treatment of a dengue infection. Persons who think they have dengue should use analgesics (pain relievers) with acetaminophen and avoid those containing ibuprofen, Naproxen, aspirin or aspirin containing drugs. They should also rest, drink plenty of fluids to prevent dehydration, avoid mosquito bites while febrile and consult a physician.

As with dengue, there is no specific medication for DHF. If a clinical diagnosis is made early, a health care provider can effectively treat DHF using fluid replacement therapy. Adequately management of DHF generally requires hospitalization.


The information in this use case was obtained from the internet and may or may not reflect current medical practice. It is for illustrative purpose only and should not be used to make any actual medical diagnosis.

The Vocabulary

This is one possible vocabulary structure:

The one-to-one associations to derivedData, symptoms and warningSigns were used to provide convenient groupings of the attributes – we could have put all the attributes at the Patient level in a single flat structure.


Alternative Vocabulary Structures

Another alternative structure is to model the symptoms (and patient vital signs) more generically with  one-to-many associations that would allow an arbitrary number of symptoms and vitals:



The advantage of this is that it allows an arbitrary number of observations and each can be dateTime stamped.  We could also add other data to the symptom – such as the severity or extent of the symptom and how rapid was the onset.

Using generic collections allows us to write rules that apply operators such as ->avg and ->max or ->min to numeric values. E.g.

Where the alias “lastFourHours” is defined by the filter:


However for the purposes of this case study we will use the flatter structure for symptoms which lists a specific boolean attribute for each symptom.

The Decision Structure

The Rule Sheets

Initial Calculations

Check for Fever

Count DHF Symptoms

Review Symptoms


Test Case


Generalizing the Solution

Accommodating additional symptoms



Rule Sheet

Test Case

Revised Rule Flow



In this rule sheet we are using a lab result to determine if the symptom “lowWhiteBloodCellCount” is present.


Notice that the Hemaglobin ranges are gender specific, whereas Trygiceride levels are age specific:


Data Model

Decision Structure


Other Nasty Viral Diseases


Ebola symptoms may include


stomach pain and loss of appetite,

cough, sore throat, and difficulty swallowing,



chest pain,

breathing problems.


Chikungunya is characterized by an abrupt onset of fever frequently accompanied by joint pain. Other common signs and symptoms include muscle pain, headachenauseafatigue and rash. The joint pain is often very debilitating, but usually lasts for a few days or may be prolonged to weeks.


West Nile Fever

West Nile is a virus capable of causing disease in humans. Symptoms and signs include feverheadache, body aches, skin rash, and swollen lymph glands. Severe symptoms may include stiff neck, sleepiness, disorientation, coma, tremors, convulsions, and paralysis. Most cases of West Nile virus are mild and go unreported.

Omsk Hemorrhagic Fever

After an incubation period of 3-8 days, the symptoms of OHF begin suddenly with chills, fever, headache, and severe muscle pain with vomiting, gastrointestinal symptoms and bleeding problems occurring 3-4 days after initial symptom onset. Patients may experience abnormally low blood pressure and low platelet, red blood cell, and white blood cell counts.

After 1-2 weeks of symptoms, some patients recover without complication. However, the illness is biphasic for a subset of patients who experience a second wave of symptoms at the beginning of the third week. These symptoms include fever and encephalitis (inflammation of the brain).

The case fatality rate of OHF is low (0.5% to 3%).

Marbugh Hemorrhagic Fever

After an incubation period of 5-10 days, symptom onset is sudden and marked by fever, chills, headache, and myalgia. Around the fifth day after the onset of symptoms, a maculopapular rash, most prominent on the trunk (chest, back, stomach), may occur. Nausea, vomiting, chest pain, a sore throat, abdominal pain, and diarrhea may then appear. Symptoms become increasingly severe and can include jaundice, inflammation of the pancreas, severe weight loss, delirium, shock, liver failure, massive hemorrhaging, and multi-organ dysfunction.

Because many of the signs and symptoms of Marburg hemorrhagic fever are similar to those of other infectious diseases such as malaria or typhoid fever, clinical diagnosis of the disease can be difficult, especially if only a single case is involved.

The case-fatality rate for Marburg hemorrhagic fever is between 23-90%. For a complete listing of the case fatality rates for previous outbreaks, please see the History of Outbreaks table

Lassa Fever

Signs and symptoms of Lassa fever typically occur 1-3 weeks after the patient comes into contact with the virus. For the majority of Lassa fever virus infections (approximately 80%), symptoms are mild and are undiagnosed. Mild symptoms include slight fever, general malaise and weakness, and headache. In 20% of infected individuals, however, disease may progress to more serious symptoms including hemorrhaging (in gums, eyes, or nose, as examples), respiratory distress, repeated vomiting, facial swelling, pain in the chest, back, and abdomen, and shock. Neurological problems have also been described, including hearing loss, tremors, and encephalitis. Death may occur within two weeks after symptom onset due to multi-organ failure.

The most common complication of Lassa fever is deafness. Various degrees of deafness occur in approximately one-third of infections, and in many cases hearing loss is permanent. As far as is known, severity of the disease does not affect this complication: deafness may develop in mild as well as in severe cases.

Approximately 15%-20% of patients hospitalized for Lassa fever die from the illness. However, only 1% of all Lassa virus infections result in death. The death rates for women in the third trimester of pregnancy are particularly high. Spontaneous abortion is a serious complication of infection with an estimated 95% mortality in fetuses of infected pregnant mothers.

Because the symptoms of Lassa fever are so varied and nonspecific, clinical diagnosis is often difficult. Lassa fever is also associated with occasional epidemics, during which the case-fatality rate can reach 50% in hospitalized patients.