What Is Bunyavirales (Bunyaviridae)?

Medically Reviewed by Jabeen Begum, MD on October 11, 2022
Written by Sarah Vallie
5 min read

Viruses can make you utterly miserable, or worse. Some may be as mild as a cold, while others are fatal. Viruses in the Bunyvirales order are no exception. While some may cause only few symptoms, others can cause hemorrhagic fever, systemic infection, and even death.

Bunyavirales is an order of viruses that were formerly known as the Bunyaviridae family. Several of the families within the Bunyavirales order cause severe illness. They include:

  • Arenaviridae. Arenaviruses are spread by rodents, mainly mice and rats, and cause many types of viral hemorrhagic fevers and a condition called lymphocytic choriomeningitis (LCM).
  • Hantaviridae. Like arenaviruses, hantaviruses are spread mainly by mice and rats. Old World hantaviruses (i.e., those endemic to the eastern hemisphere) cause viral hemorrhagic fever with renal syndrome (HFRS). New World hantaviruses, those found in North, Central, and South America, cause a condition called hantavirus pulmonary syndrome (HPS). 
  • Nairoviridae. Most nairoviruses are tick-borne, but some come from rodents. The most significant nairovirus is Crimean-Congo hemorrhagic fever virus, which causes Crimean-Congo hemorrhagic fever (CCHF).
  • Phenuiviridae. Within this family, only viruses in the genus known as Phleboviruses cause diseases in humans. Rift Valley fever is the most significant illness caused by a phlebovirus and can be passed on from an infected mosquito or fly or from contact with the blood or organs of infected animals.

Many types of viruses in the Bunyavirales family cause viral hemorrhagic fever of some kind. While symptoms vary between types of viral hemorrhagic fevers, most involve bleeding, affect multiple organ systems, cause damage to your cardiovascular system, and otherwise make it difficult for your body to function. Most viral hemorrhagic fevers don’t currently have a cure or a vaccine to defend against the initial infection.

Symptoms of Bunyavirales infection depend on which Bunyaviridae virus you have. General early signs of viral hemorrhagic fever, though, include:

  • An ache in the bones, joints, and muscles
  • Diarrhea
  • Dizziness
  • Fatigue
  • Fever
  • Nausea
  • Vomiting
  • Weakness

More severe signs of a viral hemorrhagic fever may include:

  • Bleeding from the ears, eyes, or mouth
  • Coma
  • Delirium
  • Internal bleeding
  • Kidney failure
  • Liver failure
  • Nervous system malfunction
  • Respiratory failure
  • Death

Here are some symptoms that may accompany a hemorrhagic fever based on the viruses that cause them:

Hemorrhagic fever caused by arenaviruses. The majority of arenaviruses cause some type of viral hemorrhagic fever. These include:

  • Argentine hemorrhagic fever: Symptoms of viral hemorrhagic fever, plus a higher risk of bleeding, low levels of platelets in the blood, and neurological disorders
  • Brazilian hemorrhagic fever: Symptoms of viral hemorrhagic fever, plus necrosis in the epithelial cells of the liver
  • Lassa fever: Symptoms of viral hemorrhagic fever, plus abdominal pain, with a higher risk of bleeding and low blood pressure
  • Whitewater Arroyo: Symptoms of viral hemorrhagic fever with more frequent instances of liver failure

Viral hemorrhagic fever with renal syndrome. Hemorrhagic fever with renal syndrome includes the traditional symptoms of hemorrhagic fever but also is far more likely to cause renal (kidney) failure. When your kidneys don’t work properly, they are unable to filter waste from your blood. This causes waste products to build up in your blood. 

Symptoms of renal failure include:

  • Chest pain or pressure
  • Coma
  • Confusion
  • Decreased urine output
  • Fatigue
  • Fluid retention
  • Irregular heartbeat
  • Nausea
  • Seizures
  • Shortness of breath
  • Weakness
  • Ultimately, death

Crimean-Congo hemorrhagic fever. Crimean-Congo hemorrhagic fever usually comes on suddenly. Aside from the typical symptoms of hemorrhagic fever, Crimean-Congo hemorrhagic fever also includes symptoms such as:

  • A flushed face
  • Jaundice
  • Nosebleeds
  • Red eyes
  • Red spots on the roof of your mouth
  • Red throat
  • Stomach pain
  • Severe bruising
  • Uncontrolled bleeding

Rift Valley fever. Rift Valley fever may include traditional symptoms of hemorrhagic fever but may also include: 

  • Diseases of the eye, such as lesions that may cause blurred or decreased vision
  • Inflammation of the brain (encephalitis), which may cause comas, headaches, and seizures 

Bunyavirales can cause conditions other than viral hemorrhagic fever, though, and these conditions may have different symptoms: 

Lymphocytic choriomeningitis. Mild cases of lymphocytic choriomeningitis (which is caused by an arenavirus) are the most common, but severe cases may also occur and result in neurological damage. Symptoms of lymphocytic choriomeningitis include:

  • Fever
  • Headache
  • Loss of appetite
  • Malaise
  • Muscle aches
  • Nausea
  • Vomiting

Severe cases of lymphocytic choriomeningitis may also lead to:

  • Encephalitis: Inflammation of the brain that can cause fever, headache, and (in more severe cases) seizures and motor problems.
  • Hydrocephalus: Buildup of fluid within the brain that may cause headaches, vision problems, sluggishness, poor coordination, loss of bladder control, and a decline in memory and cognition.
  • Meningitis: Swelling of the protective membranes around the brain and spinal cord that may lead to fever, irritability, lethargy, headache, a stiff neck, nausea and vomiting, and sensitivity to light.
  • Myelitis: Inflammation of the spinal cord, which may cause pain, numbness or tingling, incontinence, and weakness in your arms and legs.

Babies infected with lymphocytic choriomeningitis while in utero may be born with birth defects. If a pregnant patient catches lymphocytic choriomeningitis during the first trimester, they may miscarry.

Hantavirus pulmonary syndrome. Hantavirus pulmonary syndrome is rare but has a mortality rate of 38%. Symptoms may start to develop 1 to 8 weeks after exposure. 

Early symptoms of hantavirus pulmonary syndrome include fatigue, fever, and muscle aches, but you may also experience:

  • Abdominal pain
  • Chills
  • Diarrhea
  • Dizziness
  • Headache
  • Nausea
  • Vomiting

About 4 to 10 days after the onset of symptoms, you may also experience coughing and shortness of breath.

Bunyaviridae diagnosis is performed using laboratory testing. For the most part, treatment is limited to supportive care, but some strains of Bunyavirales have additional treatment options.

You will receive a range of treatments, depending on whether you have been infected by an:

Arenavirus. Most arenaviruses can be treated with an antiviral drug called ribavirin. However, ribavirin does not treat lymphocytic choriomeningitis. Treatment for lymphocytic choriomeningitis is mainly supportive, though some patients may benefit from anti-inflammatory medications depending on their symptoms.

Hantavirus. For both forms of hantavirus, supportive care is the primary option. A hemorrhagic fever with renal syndrome, for instance, may sometimes require dialysis to sustain kidney function. If administered early in the course of the disease, ribavirin may also decrease the severity of the illness. Supportive care is the only treatment option for hantavirus pulmonary syndrome.

Nairovirus. Some patients with Crimean-Congo hemorrhagic fever have benefited from the use of ribavirin, but otherwise, treatment mainly involves supportive care.

Phenuivirus. Current treatment for Rift Valley fever is supportive, though vaccines are also in development.