Cardiovascular and Lymphatic System Diseases

Nonhemorrhagic and Hemorrhagic Fever Diseases

Bacterial Nonhemorrhagic Fever

Common nonhemorrhagic fever diseases result from bacterial infections and include brucellosis, caused by foodborne Brucella; Q fever, caused by the zoonotic Coxiella burnetii; and Rocky Mountain spotted fever, caused by the tick-borne Rickettsia.

Nonhemorrhagic fever diseases result from bacterial infections and are associated with high fever. In contrast, hemorrhagic fevers occur from contact with animals or other people and can cause problems with the blood’s ability to clot. Some examples of nonhemorrhagic fever diseases are brucellosis, Q fever, and Rocky Mountain spotted fever. Brucellosis and Q fever use livestock as animal reservoirs, and Rocky Mountain spotted fever is spread by tick bites.

Brucellosis is caused by various species of bacteria within the genus Brucella. Humans most often acquire this disease by eating unpasteurized milk or undercooked meat. People can also acquire brucellosis if they inhale aerosolized Brucella bacteria. Inhalation exposure is rarer than exposure by ingestion but can occur in certain laboratory or slaughterhouse settings. A third means of exposure occurs when wounds in the skin or the mucous membranes are exposed to Brucella-contaminated items. Flu-like symptoms are paired with extreme muscle pain, night sweats, and a fever.

Q fever is caused by Coxiella burnetii, which naturally infects goats, sheep, and cattle. Humans become infected by breathing in dust that has been contaminated by infected animals' bodily fluids. Symptoms are flu-like and can be mild or severe. Both brucellosis and Q fever are treatable with doxycycline antibiotics.

Rocky Mountain spotted fever is caused by bacteria from the genus Rickettsia. Symptoms include fever, headache, and a rash. The rash gives the patient's skin a dotted and mottled appearance, which is where the name spotted fever originated. Rocky Mountain spotted fever can be life-threatening, but early treatment with doxycycline antibiotics can result in full recovery in the majority of cases.
Coxiella burnetii (scanning electron microscope) can lead to Q fever, which is characterized by flu-like symptoms. Rickettsia rickettsii (light microscope) is among various bacteria of the Rickettsia genus that cause Rocky Mountain spotted fever.
Credit: NIAID (left), CDC/Billie Ruth Bird (right)

Viral Hemorrhagic Fever

Hemorrhagic fever diseases result from viral infections spread from animal reservoirs.

Hemorrhagic fever is a disease caused by a specific viral infection from one of five families of RNA viruses. Early symptoms of hemorrhagic fever are cold-like and flu-like, which lead to more severe symptoms, including high fever, extensive internal bleeding, swelling, low blood pressure, and shock. Hemorrhagic fevers are spread via animal reservoirs. Hemorrhagic fevers caused by viruses include yellow fever, chikungunya, dengue, Marburg hemorrhagic fever, and Ebola.

Ebola virus and Marburg virus are well-known examples of viruses that cause hemorrhagic fevers. Due to their filamentous shapes, both Ebola virus and Marburg virus are classified in the viral family Filoviridae, known as the filoviruses. Bats are the known animal reservoir of Marburg virus and a suspected animal reservoir of Ebola virus. Both viruses are capable of person-to-person contact via bodily fluids. Supportive treatments such as fluids and rest are currently the only treatments. The mortality rates are 50% or higher regardless of treatment.
The Ebola virus and Marburg virus can both lead to hemorrhagic fever.
Credit: CDC/Cynthia Goldsmith (left), CDC/Frederick Murphy (right)