Marburg virus is a filovirus that causes a life-threatening Marburg hemorrhagic fever in humans.
Marburg virus just like the Ebola virus causes an acute hemorrhagic illness associated with high mortality due to multiorgan failure as a result of abnormal inflammatory response induced by the virus, massive bleeding, and severe fluid and electrolytes loss. This disease is considered one of the most deadly infectious diseases with a mortality rate of 25-90%. What’s more, there is no etiologic treatment so only supportive and symptomatic care can be provided. Fortunately, the outbreaks of the disease are relatively rare.
The Marburg virus and his relative Ebola virus are the representatives of the Filoviridae family which in turn belongs to the mononegavirus superfamily. The virus itself looks like the filaments that are formed into different shapes like rods, 6-shaped, U-shaped particles, and a shepherd’s crook. The threads of the virus vary in length from 800 nm to 1400 nm. Filoviruses have a single-stranded RNA that encodes the production of seven proteins.
Infection was discovered for the first time in 1967 when lab workers in Marburg, Germany, developed a severe disease after they worked with some samples from African green monkeys that apparently were infected. At that time 31 workers caught the disease, 7 of which died. Since then there were reports about occasional outbreaks of the Marburg hemorrhagic fever in African countries.
Interestingly, it still unknown how the virus is transmitted from an animal host to a human, though probably it occurs during close contact with infected animals/humans and their body fluids – the virus can enter through the breaks of the skin or mucous membranes. For instance, the virus was described in bats (namely, African fruit bat species, Roussettus aegypticus) with the outbreaks of the disease occurring after people were visiting the mines or caves inhabited by these animals. Other animal reservoirs of Marburg virus remain unidentified. Thereafter, infected humans spread the disease by a person-to-person transmission with blood or any other body fluids (tears, urine, saliva, etc.). However, it is considered that the course of the disease is somewhat milder in those who got the infection from a human in comparison to those who were in contact with an infected animal.
After the virus enters the body, it invades the cells and starts to replicate rapidly within endothelial cells, monocytes, macrophages, and dendritic cells. Due to the potent immune system reaction, the parenchymal cells found in the liver, spleen, lymph nodes and lungs undergo necrosis. The ruining of the endothelia; cells result in vascular injury and massive bleeding which along with fluid loss due to diarrhea and vomiting consecutively leads to hypovolemic shock. All this process lasts from 2 to 21 days until the first symptoms of the disease become noticeable (on average incubation period lasts from 5 to 9 days).
Usually infected individuals develop flu-like symptoms including headache and muscle aches. Fever lasts from 12 to 22 days. A few days later abdominal pain, nausea, vomiting, and diarrhea as well as cough and chest pain occur, occasionally associated with the maculopapular rash on the trunk and limbs which appear around day 5 of the disease. Other symptoms may include light sensitivity, jaundice, petechiae (small purple spots on the skin due to minor bleeds in the skin) and lymph nodes enlargement. By the end of the first week, an ill person experiences severe bleeding from multiple sites – the nose, mouth, gums and digestive tract. Additionally, internal organs are also involved – liver hemorrhage, kidney injury and heart muscle infection are typical. As week 2 of the disease begins individuals either start to recover or develop multiple organ failure. Unfortunately, in up to 90% of cases the disease eventually leads to death.
The following tests can be used in clinical settings to identify the Marburg virus infection:
- Antigen-capture enzyme-linked immunosorbent assay (ELISA) testing;
- Polymerase chain reaction (PCR);
- IgM-capture ELISA;
There is neither treatment nor the vaccine for the Marburg virus infection. The only available treatment option is to maintain blood volume and electrolyte balance with intravenous infusions of blood, plasma, and minerals, control blood coagulation and provide painkillers to relieve the pain.