1 day ago
6
Upgrade to High-Speed Internet for only ₱1499/month!
Enjoy up to 100 Mbps fiber broadband, perfect for browsing, streaming, and gaming.
Visit Suniway.ph to learn
CLINICAL MATTERS
When legendary Hollywood actor Gene Hackman and his wife Betsy Arakawa were found dead in their home under mysterious circumstances, there were many theories as to what had happened. One of the last things people expected was that a little-known virus named Hantavirus was involved in their demise. Apparently, Arakawa had contracted the virus and had quickly deteriorated and suddenly died in their home. Hackman, who had Alzheimer’s disease and heart problems, was unable to care for himself or get help and eventually died from his heart condition. What is Hantavirus, and is it something that we should be concerned about?
Hantaviruses belong to the genus Orthohantavirus in the family Hantaviridae. These viruses use RNA as their genetic material and are primarily found in rodents, where they typically cause an asymptomatic, persistent infection. Zoonotic infection of humans can occur with exposure to infected rodents and other animal hosts such as bats, moles and shrews. Hantaviruses cause two distinct clinical syndromes: hantavirus pulmonary syndrome (HPS), which was what Betsy Arakawa was diagnosed with and died of, and hemorrhagic fever with renal syndrome (HFRS). While hantavirus-like syndromes have been described in historical texts as far back as the fifth century BCE, it was only in modern times that the causative agent was finally identified. HFRS was first suspected in a large outbreak among soldiers near the Hantan River during the Korean War. The virus was finally isolated in 1978 and named Hantaan virus after the river. Since then, other related virus species have been discovered to cause HFRS or HPS, and this group of viruses is now collectively known as hantaviruses.
HPS is the syndrome that occurs more commonly in the Americas and can kill 30 to 60 percent of infected patients. Two hantaviruses, the Andes virus and Sin Nombre virus, are responsible for most of the cases of HPS. The incubation period for the disease is anywhere from one to eight weeks from the time of exposure. Early symptoms are not specific and include fever, malaise, headaches, muscle pains, and shortness of breath. Low platelet counts also occur, along with leakage of fluid from the capillaries, similar to that seen in dengue fever. As the disease progresses, the heart and lungs become affected and the patient can develop irregular heart rhythms, and fluid can build up in the pleural cavity. Fluid leaking into the air sacs of the lungs (pulmonary edema) can cause acute respiratory distress syndrome, leading to
sudden respiratory failure and death. There is no specific treatment for HPS other than supportive care. If the patient survives, recovery can be prolonged over weeks to months. HFRS is the form more commonly seen in Europe, Africa, and Asia. It can be caused by several different hantaviruses, including Hantaan virus, Seoul virus, Dobrava-Belgrade virus, and Puumala virus. HFRS can range in severity depending on the causative virus and host factors.
The signs and symptoms seen in severe HFRS are very similar to severe leptospirosis. Patients can present with fever, jaundice, dark urine, bloody diarrhea, and low platelets. Acute kidney failure and pulmonary hemorrhage can occur just like leptospirosis, and some patients, if they survive, develop long-term kidney problems leading to the need for permanent dialysis. HFRS is less deadly than HPS, with fatality rates ranging from one to 15 percent, but can still be quite debilitating. Similar to HPS, patients can take a long time to recover as well.
Hantavirus is transmitted from infected animal reservoirs to humans through inhalation of infected body fluids, including respiratory droplets, aerosols, urine, feces, and saliva. Some hantaviruses can be acquired through tick and mite bites, ingestion of contaminated food, and through bites and scratches from infected animals. Human-to-human transmission is rare, although transplacental transmission from mother to infant has been documented. Living in
rural areas, hiking in forests, and handling rodents and other animal reservoirs can increase the risk of infection. In the case of Betsy Arakawa, she likely acquired hantavirus infection from the deer mouse, which is the usual reservoir in New Mexico, where she and her husband lived.
Diagnosis of hantavirus infection is usually made through the recognition of a clinically compatible syndrome coupled with laboratory testing. Routine laboratory tests typically show low platelets, increased creatinine associated with kidney damage, and elevated liver enzymes.
A chest x-ray in HPS can show bilateral pleural effusions (fluid in the pleural cavity on both sides) as well as signs of congestion, suggesting fluid in the air sacs of the lungs. Definitive diagnostic tests include serology, which looks at antibody titers to hantavirus (IgM and IgG), as well as, PCR. These confirmatory tests are not readily available and may need to be sent out to specialized research and surveillance laboratories. No specific antiviral treatment has been
developed, and no vaccines have been approved. Infection with one species of hantavirus is thought to confer lifelong immunity to that specific virus, although infection with other species can occur.
A serologic study in the Philippines showed that 6.1 percent of a nationally representative sample of patients were positive for hantavirus despite not having any history of specific symptoms, which suggests that infection is more widespread than previously thought. Hantaviruses have been found in animals in the Philippines, and a new species of hantavirus was discovered in 2016 in fruit bats in Quezon Memorial National Park and named Quezon virus (QZNV). No human cases of Quezon virus have been documented at this time.
In 1992, a report was published involving two Filipino patients in San Lazaro Hospital presenting with jaundice and abdominal pain, both of whom tested positive for high titers of Hantavirus antibodies. Both patients survived and had a relatively mild course. These two cases demonstrate that symptomatic hantavirus infection does occur in the Philippines and is probably just underdiagnosed. Many more cases of HFRS may be misdiagnosed as leptospirosis since there is limited testing available. The case of Betsy Arakawa demonstrates that we disregard these viruses that lurk in plain sight at our peril. With this in mind, the Philippine government and our academic centers should continue investing in surveillance systems to detect unknown and little-known viruses to protect our population from the ever-present threat of these emerging and re-emerging infectious diseases.
