Rift Valley Fever (RVF) Virus

Written by Kristen Fischer
Medically Reviewed by Shruthi N, MD on April 24, 2025
5 min read

Rift Valley fever (RVF) is a disease animals can get when they're bitten by a mosquito carrying the Rift Valley fever virus (RVFV). Humans can get RVF if they're bitten by a mosquito infected with the virus or if they come in contact with the blood or tissues of an infected animal.

RVF is most common in animals living in sub-Saharan Africa, including camels, cattle, sheep, goats, and buffalo. To date, there have been no reported cases of people catching it from other people.

The virus gets its name from Kenya's Rift Valley region, where it was discovered in 1931. Since then, there have been many outbreaks on the African continent. But experts believe that the rise in global commerce and travel by humans, plus climate change, could spread RVF across the globe.

Animals get RVF from infected mosquitoes, but blood-feeding flies may carry it as well.

People can get Rift Valley fever if they're bitten by an infected mosquito. Humans can also get the virus if they have contact with an infected animal's blood, body fluids, or tissues during slaughtering, butchering, animal birth, veterinary procedures, or when getting rid of carcasses. This puts people like herders, farmers, veterinarians, and slaughterhouse workers at higher risk of being infected.

As long as infection control practices are in place, people don't seem to be able to spread it to each other. And if practices are followed when people come into contact with infected animals, it can reduce the chance of transmission.

Most people who have the virus don't have any symptoms. It's rarely serious in humans, but it can be fatal in rare cases. (It's often more severe in animals.)

Rift Valley fever signs in humans are usually mild and may include:

  • Flu-like fever muscle
  • Joint pain 
  • Headache
  • Neck stiffness
  • Sensitivity to light
  • Loss of appetite
  • Vomiting

About 8%-10% of people will have a more severe form of the virus. Those symptoms include:

Animals can get severely ill from RVF, but their symptoms will vary depending on the species, age, and whether the animal is pregnant. Young lambs and goats (kids) are most at risk for RVF, followed by sheep and their calves. Goats, African buffalo, domestic buffalo, Asian monkeys, and humans are among the least susceptible, though they can still get Rift Valley fever and may not have any symptoms.

Rift Valley fever signs in animals may include:

  • Fever 
  • Listlessness
  • Anorexia
  • Abortion
  • High mortality in newborns

Rift Valley fever can be very hard to diagnose; there are no specific Rift Valley fever tests, and the virus can only be detected in the blood briefly. RVF is often confused with viral or bacterial diseases such as malaria, meningitis, and cholera.

To diagnose Rift Valley fever, doctors will discuss a patient's history to check if they've been around something like animal slaughtering, births, or carcasses, or veterinary procedures where they could have been exposed to the virus. Or if they've traveled where the has been an outbreak of RVF.

An RVF diagnosis requires one of the following blood tests:

  • Virus neutralization test (VNT)
  • Indirect immunofluorescent assay (IFA)
  • IgG and IgM antibody enzyme-linked immunosorbent assay (ELISA)

Recovery from Rift Valley fever usually doesn't require any specific treatment, as most cases are mild and short. Over-the-counter medications, such as ibuprofen or acetaminophen, can help manage symptoms like fever and body aches. 

People with more severe cases are usually hospitalized and get supportive care for symptoms and complications.

A small percentage of people who have severe symptoms experience the following complications:

  • Lesions on the eyes
  • Blurred or decreased vision
  • Permanent vision loss
  • Headache
  • Coma
  • Seizures
  • Jaundice
  • Liver problems
  • Vomiting blood
  • Bloody stool
  • Death

Most people recover within two to seven days after they feel ill. Only about 1% of people with RVF die from the disease.

These are a few ways to avoid getting RVF:

  • Pay attention to travel advisories if you're traveling globally. They can help you tell if you're going to an area with an outbreak.
  • Take precautions to avoid mosquito bites, such as using mosquito repellent and wearing long-sleeved shirts and pants. Outbreaks often happen in areas that get ongoing rain, which can raise mosquito activity.
  • Use protective gear if you expect to come into close contact with animals in an affected region.

Rift Valley fever vaccine

There is an experimental vaccine for humans that's been tested on people at high risk for RVF, such as veterinarians and lab workers who treat animals. There's no commercially available form of a vaccine for the general public.

Vaccines for animals exist, which may reduce the spread of the virus. Efforts to vaccinate animals have been difficult. That's because safer vaccines require multiple dosing, and live virus vaccines can cause birth defects and lead to fetal death in livestock. Another problem is that areas often lack electricity to safely store the vaccines.

Some experts say global warming could raise the risk of Rift Valley fever and make it more widespread. As temperatures rise, it could expand where mosquitoes can spread the virus. Mosquitoes are vectors (meaning they carry the virus) and can transmit the virus more often after heavy rainfall. Climate change can shift the ecology of mosquitoes, so it can affect human (and animal) health.

The World Health Organization (WHO) considers Rift Valley fever as one of the eight diseases that pose the greatest public health risk of becoming an epidemic. This helps the organization prioritize tests and treatments, including vaccines. Researchers are looking at multiple vaccine agents in hopes to develop one that's safe and effective.

Is Rift Valley fever zoonotic?

Yes, RVF is zoonotic, which means it mostly affects animals, but it can be transmitted to humans from animals.

What is the incubation period of Rift Valley fever?

The incubation period for RVF can last between two and six days.

What is the classification of Rift Valley Fever virus?

Rift Valley fever (RVF) virus is an arbovirus in the Bunyaviridae family.