Hantavirus Disease : Many diseases, oftentimes, surprise us and catch us off guard. We can do a lot of things to prepare and protect us against different illnesses like boosting our immune system or regular consultation with health experts. But some diseases will just be in front of outdoor steps knocking, or even already inside our homes.
There are many ways we can get infected by infectious diseases. One of which is through vectors. Vectors are living organisms that carry and transmit disease-causing agents into another living organism. Examples of vectors are mosquitoes, rodents, fleas, and aquatic snails.
Rodents are one of the major vectors of diseases. Worldwide, they spread and transmit over 35 diseases. Hantavirus is among the great clinical concerns transmitted by rodents.
Hantaviruses can cause infection of different disease syndromes in people. Hantaviruses can cause both hemorrhagic fevers with renal syndrome (HFRS) and hantavirus pulmonary syndrome (HPS).
Discovery Through Outbreaks
The earliest record depicting a disease that resembles HFRS was found by Dr. Ho Wang Lee. The Chinese medical recording dates back to 960 A.D. In 1913, records describing hemorrhagic fever with the renal syndrome were found in medical records in eastern Siberia, Russia.
Hantavirus pretty much evaded public attention up until the 20th century. The discovery of hantaviruses can be attributed to two major outbreaks.
The first recorded hantavirus outbreak happened during the Korean War of 1951 to 1953. Around 3,000 United Nations troops deployed in Korea fell ill with Korean hemorrhagic fever, now referred to as HFRS. Ten to fifteen percent died. In 1978, the causative agent of Korean hemorrhagic fever was isolated from infected small striped field rodents, Apodemus agrarius, near the Hantan river in South Korea. They initially named the discovered virus Hantaan, named after the river where the infected rodents were found.
They observed that hantaviruses do not have arthropods as vectors. They establish exclusive infection on certain specific hosts. In 1981, the genus Hantavirus was formed.
The second major hantavirus outbreak happened in the Four Corners region of the southern United States of America in 1993. A Navajo man with shortness of breath was rushed to the hospital but died there rapidly. Upon investigation, five similar cases were reported and all died after respiratory failure. In the next following weeks, several additional cases were reported.
Virologists were able to link the disease to an unknown type of hantavirus. In order to know more about the disease, researchers trap many different species of rodents living in the Four Corners region. They were able to isolate the hantavirus on deer mouse, Peromyscus maniculatus.
Hantaviruses and Its Transmission
Hantaviruses are spherical or oval virions around 80 to 120 nanometer in diameter. They have enveloped RNA. Hantaviruses belong to the family Bunyaviridae. This family, which consists of around 300 viruses, infects different organisms such as arthropods, humans, and plants.
Rodents are known to be the natural hosts of hantaviruses. Specific hantavirus is carried by specific rodents. Hantaviruses can be classified into two basic groups of disease. The first is the Old World hantaviruses that are found in Asia and Europe and responsible for hemorrhagic fevers with renal syndrome. And the New World hantaviruses that are found in America and the cause of hantavirus pulmonary syndrome.
The usual route of transmission for both diseases is the inhalation of the virus through the lungs. People might get infected by hantavirus upon exposure in the urine, droppings, or saliva of an infected rodent. When fresh urine, droppings, or nesting material from an infected rodent are stirred up, droplets with the virus get into the air. This is called airborne transmission.
Transmission can also happen when infected urine, droppings, or saliva has direct contact into open wounds or abrasions or into the mucous membranes of nose, eyes, or mouth.
It is also possible to get infected with contaminated food. Transmission from human to human is possible but extremely rare.
Hemorrhagic Fevers with Renal Syndrome
Epidemics of hemorrhagic fevers with renal syndrome happens mainly in Asia and Europe. Annually, about 100,000 cases are being recorded and China is the most affected.
The incubation period of HFRS is around 4 days to 49 days. Clinical manifestation occurs in 5 phases namely, febrile, hypotensive, oliguric, polyuric, and convalescent.
The initial onset of the disease is characterized by fever with severe headache, nausea, weakness, loss of appetite, and myalgia. Infected patients may also experience redness of the eyes, flushing of the face, and rash. Patients will later experience vascular leakage, low blood pressure, and acute kidney failure.
Most of the patients recover completely. The duration of recovery depends on the rate of normalization of renal function. The death rate of the disease is around 5 to 15%.
Hantavirus Pulmonary Syndrome
Hantavirus pulmonary syndrome is a rare but severe and can be a life-threatening disease. It is primarily carried by the deer mouse and the disease happens mostly in North America.
The clinical symptoms have two distinct phases. The initial or first stage appears to be flu-like symptoms. These include fever, muscle aches, and fatigue. It can also be accompanied by headaches, chills, vomiting, and abdominal pain.
After 4 to 10 days from the initial phase, the late or serious symptoms appear. Symptoms include shortness of breath, cough with secretions, low blood pressure, and fluid in the lungs.
When the lungs of the patient begin to fill up with fluid, breathing becomes difficult then organs begin to fail, especially the heart. The death rate of the disease can reach up to 30%.
At the moment, there is still no vaccine against hantaviruses. Unfortunately, there is also no specific cure and treatment for hantavirus infections. Patients may do better with supportive medical and intensive care.
The earlier the patient is diagnosed, the better. Several laboratory tests can be done to detect the infection. A serological test or even a CT scan can be used to confirm the illness.
The best way to prevent hantavirus infection is to eliminate or control its primary vectors which are rodents. We should keep rodents out of our homes and workplace. There are a lot of ways to do it like setting traps and blocking access to rodents.
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