What is Filovirus?

Filoviruses, from the virus family named Filoviridae, are known to cause severe bleeding diseases, or ‘hemorrhagic fevers’, in humans and primates. This family is made up of three types, or ‘genera’, known as Cuevavirus, Marburgvirus, and Ebolavirus. Within these, there are six subdivisions, or ‘species’: Zaire, Sudan, Tai Forest, Bundibugyo, Reston, and Bombali. So far, it’s believed that the Reston and Bombali types don’t cause illness in humans.

The term ‘filoviruses’ comes from the Latin word ‘filum’, meaning ‘thread’, because under a microscope, these viruses look like threadlike or ring-shaped structures. Encased in a protective outer part, or ‘envelope’, these viruses carry a genetic code composed of a single string of RNA, a molecule similar to DNA, arranged in a straight line. They also have a single spike-like structure on their surface made of a type of protein called a ‘glycoprotein’, and four structural proteins, including a virus-made, or ‘virus-encoded polymerase’. These filoviruses are highly contagious and can spread rapidly through person-to-person contact. These viruses require the highest level of safety precautions, or ‘biosafety level 4’, because they are associated with high death rates.

What Causes Filovirus?

The Ebola virus has the ability to infect a wide range of cells. It does this by attaching itself to a cell using a part of the virus called a surface glycoprotein. Once attached, the virus enters the cell through a process known as macropinocytosis, which is essentially when the cell ‘swallows’ the virus. The ability of the virus to attach to the cell is connected to certain elements within the cell called acid sphingomyelinase and plasma membrane sphingomyelin.

The attachment process from the virus side is managed by its own glycoprotein, structured as three pairs, each having a binding and fusion partner. Once the virus manages to enter the cell, it moves to a part of the cell called the late endosome. Here, a protein named cysteine protease activates a component of the surface glycoprotein, which allows the virus to blend in with the endosome membrane. This process allows the virus to release its own nucleus-like structure (nucleocapsid) into the cell’s substance (cytoplasm), leading to the creation, duplication, and release of new virus cells.

When the infection starts, the virus can spread to multiple cell types, potentially leading to generalized organ failure as many different cells can be affected.

Risk Factors and Frequency for Filovirus

The filovirus, which includes the ebolavirus, was first discovered in 1976. Since then, there have been over twenty outbreaks, mostly occurring in sub-Saharan Africa in countries like Sudan, Uganda, Democratic Republic of Congo, and Gabon. The largest known outbreak of ebolavirus happened between 2013 and 2016 in West Africa, affecting both rural and urban areas. This outbreak resulted in over 28,000 infections and 11,000 deaths, but the actual figures might be even higher due to under-reporting. Although most ebolavirus outbreaks have been in African countries, cases have also been reported in Spain and the USA due to international travel.

The filovirus was first discovered in 1976.
There have been over twenty known outbreaks mainly in sub-Saharan Africa.
The largest known outbreak occurred in West Africa from 2013 to 2016.
This outbreak resulted in over 28,000 infections and 11,000 deaths.
Cases have also been reported outside of Africa, in countries like Spain and the USA.

Fruit bats of the Pteropodidae family are currently believed to be the natural hosts of the ebolavirus. However, scientists have not been able to isolate the virus in bats under natural conditions. It is likely that the virus is transmitted to humans when they handle infected forest animals. The virus can also spread from person to person through direct contact with infected body fluids.

Signs and Symptoms of Filovirus

When trying to diagnose any illness, it’s crucial to get a detailed overview of the patient’s health history and do a physical examination. In the case of filoviruses, which are a type of virus, extra attention should be paid to any recent travel, potential exposure to the virus, and any contact with others who are ill. Doctors need to understand what symptoms the patient has, how long they’ve been experiencing them, and when they started. Some common symptoms include a fever that comes on suddenly, nausea, vomiting, diarrhea, muscle pain, fatigue, headache, stomach ache, and unexplained bleeding.

These symptoms typically start to show up anywhere from 2 to 21 days after the person has been in contact with the virus, with it usually taking about 8 to 10 days. Because the symptoms are fairly common, they might initially get mistaken for the flu or malaria. Not everyone with a filovirus will experience bleeding, but it does occur in around 30 to 50% of patients and often involves bleeding from mucous membranes, particularly those in the digestive and urinary tracts.

Fever that comes on suddenly
Nausea
Vomiting
Diarrhea
Muscle pain
Weakness
Headache
Stomach ache
Unexplained bleeding (in some patients)
Symptoms start 2 to 21 days after exposure (usually 8 to 10)

Testing for Filovirus

If you’re feeling unwell, your doctor will first take your medical history and conduct a physical examination. They may also order general lab tests that could show signs of lower than normal fluid levels in your bloodstream because of fluid loss from your stomach and intestines. The lab tests might also reveal problems with your liver and kidneys.

To know for sure if there’s a filovirus infection – which includes viruses like Ebola – your doctor will order tests to identify traces of the virus, its proteins or its RNA from your blood, serum, or plasma. RNA nucleic acid amplification testing, which helps identify the virus’s genetic material, is the preferred method. However, this kind of testing can pose a significant risk of infecting lab staff, and it must be handled with extreme caution due to the high risk of spreading the virus.

To definitely confirm filovirus infection, the virus needs to be isolated in the lab. IgM testing, which examines your body’s initial immune response, can help diagnose the illness during the recovery period. IgG testing, which monitors your body’s long-term immune response, is typically only used for tracking disease spread in a community.

The 2016 Ebola outbreak motivated the development of rapid diagnostic tests. There are now five tests approved specifically for diagnosing Ebola. These tests work in the same way as an ELISA test, which uses antibodies to identify and capture the virus antigens – the substances that trigger an immune response in the body. However, these rapid tests are designed to be simpler and quicker to use, allowing faster results with less processing. Rapid testing helps control outbreaks faster and prevents the virus from spreading further.

Treatment Options for Filovirus

The management of diseases caused by filoviruses like Ebola often involves prevention, detection, and supportive care. There are very few trials studying specific treatments for Ebola. One trial studied the use of ZMapp, an antibody-based medicine, in 72 people and compared it to standard care. The results showed a lower death rate in the group treated with ZMapp (22% compared to 37% in the standard care group). Another study compared intravenous fluid therapy to oral hydration in 424 patients, finding no significant difference in survival rates after 28 days.

Different types of treatments have been studied with unclear or limited results. For instance, convalescent plasma (blood plasma from people who have recovered from the virus) has been examined in a couple of studies. These studies reported decreased death rates with the use of convalescent plasma, but these results were limited due to factors like small sample sizes, lack of random selection of participants, incomplete data on other treatments given to the patients, and unknown levels of neutralizing antibodies in the plasma.

Another medicine studied is favipiravir, which was found to be well-tolerated in a group of 99 patients and reported a reduction in the death rate. However, this study also faced similar limitations. Another drug, Interferon beta 1-a, showed a reduction in mortality rates in a study, but again, this study was limited by a small sample size and lack of randomization.

Palliative care, focused on relieving symptoms and improving quality of life, has been suggested as a vital component in the treatment of these diseases. This is primarily due to the high fatality rate, the absence of clearly effective treatment, and the stressful nature of outbreaks. Palliative services can help manage pain and other symptoms, decrease emotional and social stress, and improve the overall quality of life for patients.

Some other scientific studies have recognized certain agents which are not specific to the Ebola virus but may assist in the treatment. Medications such as amiodarone, an ion channel inhibitor which prevents the virus from entering cells, have been investigated. However, these studies haven’t shown any improvement in treatment during real-world outbreaks. Some antiparasitic drugs like chloroquine, which is known to have antiviral properties, and some psychoactive drugs have also been considered due to their ability to inhibit viral replication. However, human studies haven’t confirmed their effectiveness in treating Ebola.

Progress has been made in vaccine development. During the 2014 to 2016 outbreak, two vaccines underwent advanced testing and showed promise against the Ebola virus, demonstrating high effectiveness and long-term antibody responses. However, there’s still no vaccine for Marburgvirus, a different filovirus.

If someone has journeyed to regions where Ebola virus or Marburg virus are common or there have been known outbreaks, it’s important to consider these as possible diagnoses. However, identifying these infectious diseases can be tough due to the vague initial symptoms of a viral infection and fever.

The similarity of these symptoms can lead to confusion with other illnesses, such as:

Malaria
Typhoid fever
Influenza (the flu)
Crimean-Congo hemorrhagic fever
Acute surgical abdomen
Cholera
Other hemorrhagic fevers like dengue, Lassa, and yellow fever

What to expect with Filovirus

The outlook for people infected with filoviruses (a type of virus that includes Ebola and Marburg) is generally quite bleak. There are few treatments available and the death rate can vary between 30% and 70%. This prognosis can worsen based on the age of the patient and their nutritional health.

On a hopeful note, during the 2014 to 2016 outbreak, vaccines were tested in advanced stages of clinical trials (phase II/III), which are important steps in ensuring the safety and effectiveness of a potential new vaccine.

Possible Complications When Diagnosed with Filovirus

In serious cases of the disease, individuals typically pass away about 6 to 16 days after first noticing symptoms. The usual reasons for this are a severe, life-threatening reaction by the body and failure of multiple vital body organs, especially the liver and kidneys. Additionally, a low platelet count in the blood (which can lead to bleeding problems) and blood clotting disorders also contribute to this issue.

Major Problems:

Severe, life-threatening body reaction
Failure of multiple vital organs
Liver failure
Kidney failure
Low platelet count resulting in bleeding issues
Blood clotting disorders

Preventing Filovirus

The goal of public health measures is to control the spread of diseases and try to limit their transmission within healthcare facilities and the larger community. This includes the work done by the World Health Organization (WHO), which coordinates a global response to outbreaks through its Global Outbreak Alert and Response network.

A great example of successful disease control is in Uganda, where strong political support has helped to establish local task forces, educate the public, coordinate effective responses, use community resources promptly, and maintain efficient laboratory systems.

When cases of confirmed or suspected filovirus infection are detected, these should be managed in isolation units within the affected communities. The filovirus family includes diseases like Ebola and Marburg, known for their high death rates.

It’s essential for patients to be aware of the high mortality rates associated with these types of infections and understand how they’re spread, including through body fluids and sexual transmission. Underscoring the importance of reporting suspected cases and discouraging home treatment should be key components of public health education efforts. This helps healthcare providers to better manage and contain these serious diseases in the community.