What are Viral Hemorrhagic Fevers (VHFs)?
Viral Hemorrhagic Fevers are a group of illnesses, which are caused by various families of viruses. "Viral Hemorrhagic Fever" is a term used for describing a condition where multiple organ systems in the patient’s body are affected. The characteristic of this disease is that there is damage to the overall vascular system with impairment in the body's ability for regulating. Other symptoms of Viral Hemorrhagic Fever which the patient experiences include bleeding (hemorrhage); where the bleeding on its own is rarely fatal. There are some types of viruses, which cause hemorrhagic fever, which produces only mild illnesses in the patient. On the other hand, there are many viruses which can cause serious and life-threatening disease. In rare cases, other bacterial and viral infections can also cause viral hemorrhagic fever, a good example of which is scrub typhus.
Grouping of Hemorrhagic Fever Viruses
The cause of Viral Hemorrhagic Fevers is viruses, which belong to four distinctive families that are arenaviruses, bunyaviruses, filoviruses and flaviviruses. Some of the common features which are shared by these families are:
- The viruses are found in regions where their host species live.
- All these four family of viruses are RNA viruses, which are covered in a lipid (fatty) coating.
- Outbreaks of hemorrhagic fevers in human beings caused by these viruses tend to occur irregularly and sporadically due to which it is not easy to predict their occurrence.
- The survival of these viruses depends on an insect or animal host known as the natural reservoir.
- Human beings are not the natural reservoir of these viruses and humans get infected when they come into contact with the infected hosts. In case of some viruses, they can get transmitted from one person to another.
- Except in a few cases, VHFs do not have any cure or an effective established drug treatment.
Carrier of Viruses Which Cause Viral Hemorrhagic Fevers
Most of the viruses that cause viral hemorrhagic fevers are zoonotic, which means that arthropod vector or animal reservoir hosts are where these viruses normally reside. These viruses are completely dependent on their hosts for replication as well as survival. For majority of the viruses which cause Viral Hemorrhagic Fever, arthropods and rodents are the main reservoirs. Some of the reservoir hosts of these viruses include the cotton rat, deer mouse, house mouse, multimammate rat and other field rodents. Mosquitoes and ticks act as vectors for a few of the illnesses. In some cases, the hosts of some of the viruses are not known, the examples of which are Marburg and Ebola viruses.
Geographical Areas where Viral Hemorrhagic Fevers are Found
Collectively the viruses which cause viral hemorrhagic fevers are distributed all over the world. As each of the virus is related to one or more specific host species, so the virus and the resulting disease is commonly seen where the host species reside. Some of the hosts, such as rodent species which carry many new world arenaviruses reside in geographically restricted regions, which makes the risk of contracting viral hemorrhagic fevers caused by these viruses limited only to those regions. There are other hosts, which can be present all over the continents, such as the rodents which carry the viruses that cause different types of diseases such as Hantavirus Pulmonary Syndrome (HPS) in South and North America. Also viruses ranging in different parts of the world include different type of rodents, which carry viruses that cause hemorrhagic fever with renal syndrome in Asia and Europe. Some of the hosts are distributed throughout the world, e.g. the common rat which can carry the Seoul virus. In some cases, people can become infected from a host which has been exported from its native environment.
Transmission of the Viruses Which Cause Viral Hemorrhagic Fevers
The hemorrhagic fever viruses are transmitted to human beings when there is overlapping of the activities of the infected reservoir vectors or hosts and the humans. The viruses which are carried by the rodent reservoirs get transmitted to humans when they come into contact with fecal matter, urine, saliva or other excretions from the body of the infected hosts. The viruses which are carried by the arthropod vectors commonly get transmitted when the vector tick or mosquito bites a human or when a human crushes a mosquito/tick. In some cases, these vectors can also spread virus to animals which are cared by the humans, e.g. livestock, which can lead to human beings getting infected when they are looking after or slaughtering the animals.
There are few hemorrhagic fever viruses which can spread from one individual to another, after one person gets infected. Some of the examples of such viruses are Marburg, Ebola, Crimean-Congo and Lassa Hemorrhagic Fever Viruses. A person can get infected from this kind of secondary transmission of the virus directly from close contact with the infected individuals or the fluids from their body. There can be an indirect transmission also, such as occurring through contact with objects that are contaminated with infected fluids of the human body, e.g. contaminated needles and syringes that have played a vital role in spreading the infection in outbreaks of Lassa fever and Ebola hemorrhagic fever.
Signs & Symptoms of Viral Hemorrhagic Fevers
Symptoms of Viral Hemorrhagic Fevers depend on its type. Patient’s initial symptoms commonly comprise of significant fever, dizziness, fatigue, loss of strength, muscle aches and exhaustion. Patients suffering from severe cases of Viral Hemorrhagic Fevers can also have signs of bleeding beneath the skin, in the internal organs or from orifices of the body, such as eyes, mouth or ears. Blood loss is rarely the cause of death even if the patient is having bleeding from different sites of the body. Symptoms seen in severe cases, where the patient is extremely ill, include shock, malfunction of the nervous system, delirium, coma and seizures.
Treatment of Viral Hemorrhagic Fevers
Currently, there is no established cure or specific treatment for Viral Hemorrhagic Fevers. Supportive therapy is given to the patient, which includes anti-viral drugs, such as Ribavirin which is known to be effective in treatment of patients having HFRS or Lassa fever. Convalescent plasma is also known to be successful in few of the patients suffering from Argentine Hemorrhagic Fever.
Prevention & Management of Viral Hemorrhagic Fevers
Vaccine is present for Argentine hemorrhagic fever and yellow fever. Other than these, there are no vaccines present, which can protect a person from Viral Hemorrhagic Fevers. Therefore, it is important to try to prevent from contracting Viral Hemorrhagic Fever by avoiding any contact with the host species. If the prevention modalities fail and a person does develop Viral Hemorrhagic Fever, then all serious efforts should be undertaken for preventing further transmission of this disease from one person to another in cases where the transmission of the virus is done in this manner, as rodents are the majority of the hosts which carry hemorrhagic fever viruses. Some of the prevention efforts are:
- Controlling the populations of the rodents.
- Making sure that the rodent droppings and nests are cleaned properly.
- Discouraging the rodents from living or entering homes or workplaces.
- Prevention efforts for hemorrhagic fever viruses which are spread by arthropod vectors should concentrate on community-wide control of arthropods and insects. Other than this, it is important to wear proper clothing, use insect repellant, window screens, bed nets and other insect barriers.
- Prevention efforts for hemorrhagic fever viruses, which are transmitted from one person to another comprise of preventing close physical contact with infected individuals and their body fluids.
- Infection control techniques and barrier nursing include wearing protective clothing and isolating the infected patient.
- Further infection control includes disinfection, proper use and disposal of the equipment and instruments, such as thermometers, needles etc. which are used for caring or treating the patients suffering from Viral Hemorrhagic Fevers.
Important Facts about Viral Hemorrhagic Fevers
- Viral Hemorrhagic Fevers (VHFs) belong to a class or a group of illnesses, which are caused by viruses that cause vascular damage resulting in symptomatic hemorrhage (bleeding).
- Viral hemorrhagic fevers are commonly associated with only one specific type of species due to which this disease is often contained within geographically limited regions; however, this disease becomes prevalent if the virus enters the humans.
- Hemorrhagic fever viruses are primarily zoonotic diseases, which are caused by viruses residing in arthropod or animal hosts.
- The common mode of transmission of hemorrhagic fever viruses is often animal or arthropod hosts. However, sometimes, the viruses which are carried by the arthropod or the animal can get transmitted to humans when they come in contact with the feces, urine, saliva and other body fluids of infected arthropods or animals. In some cases, person-to-person transmission can occur when an uninfected individual comes in contact with body fluids of the infected person.
- Some of the common symptoms of viral hemorrhagic fevers include: Fever, fatigue, weakness, muscle aches, dizziness. In cases of severe infections, patients will have bleeding under the skin, in the internal organs and sometimes from orifices of the body, such as mouth, ears or eyes. Sometime, patients can suffer from severe diarrhea, which can also be bloody. More serious symptoms consist of shock, seizures, delirium, kidney failure and coma which usually results in death.
- There is no cure for viral hemorrhagic fevers and only supportive treatment can be done for the patients. Antiviral medicines, such as Ribavirin, is effective in treating some patients who are suffering from Lassa fever. Convalescent plasma treatment is also effective in some patients.
- There are no vaccines for viral hemorrhagic fevers except for Argentine hemorrhagic fever and yellow fever. Prevention and control comprises of avoiding contact with the host vectors, species and humans who are infected with these viruses.
- Lot of studies and research is going on to deal with the menace of viral hemorrhagic fevers to human beings by trying to develop molecular, immunological and containment methods for preventing this disease.