By Budi Oetomo Narendra 
Ebola virus disease (EVD) and hantavirus infections have recently drawn significant attention, underscoring the persistent and evolving threats posed by zoonotic pathogens to global public health. While distinct in their viral families, modes of transmission, and clinical manifestations, both diseases share the critical characteristic of presenting with non-specific, flu-like symptoms in their early stages, necessitating stringent infection prevention and control (IPAC) measures to avert broader transmission and mitigate severe outcomes. The medical community, particularly healthcare professionals, has been urged to remain vigilant, with recent articles in the CMAJ (Canadian Medical Association Journal) providing essential updates and guidance on these high-risk conditions.
The renewed focus on these pathogens is a stark reminder of the dynamic interplay between human populations, animal reservoirs, and environmental factors, which continually shapes the landscape of infectious diseases. For Ebola, ongoing outbreaks in Central Africa underscore the virus’s endemic nature in certain regions and the challenges of containment, even with advancements in medical countermeasures. Hantavirus, while typically causing sporadic cases, carries a high fatality rate for specific syndromes and presents a constant, albeit usually localized, threat, especially in regions with high rodent populations. Understanding the nuances of each disease, from their origins and epidemiology to their clinical management and public health implications, is paramount for effective response and preparedness.
Hantavirus: A Persistent Zoonotic Threat with Regional Variances
Hantaviruses, members of the Hantaviridae family (within the Order Bunyavirales), are a group of RNA viruses primarily carried by rodents, which shed the virus through their urine, feces, and saliva. Humans typically contract hantavirus by inhaling aerosolized particles of these excretions, or less commonly, through direct contact with infected rodents or their bites. The disease is nationally reportable in Canada, where approximately four to five cases are confirmed annually and reported to public health authorities. These infections predominantly occur in agricultural areas of Western Canada, specifically Manitoba, Saskatchewan, Alberta, and British Columbia, aligning with the distribution of specific rodent hosts.
Historical Context and Viral Diversity
The first hantavirus, Hantaan virus, was identified in the Hantaan River area during the Korean War in the early 1950s, causing hemorrhagic fever with renal syndrome (HFRS) among soldiers. Since then, numerous hantavirus strains have been identified globally, each associated with specific rodent reservoirs and distinct clinical syndromes. In North and South America, hantaviruses such as Sin Nombre virus (carried by deer mice, Peromyscus maniculatus) are primarily responsible for hantavirus cardiopulmonary syndrome (HCPS), a severe and often fatal respiratory illness. In contrast, European and Asian hantaviruses, including Puumala virus (carried by bank voles, Myodes glareolus) and Dobrava-Belgrade virus (carried by yellow-necked mice, Apodemus flavicollis), are more commonly associated with HFRS, characterized by hemorrhagic manifestations and kidney dysfunction. The geographical distribution of these syndromes directly correlates with the habitat of their respective rodent hosts.
Epidemiology and Risk Factors in Canada
In Canada, the Sin Nombre virus is the predominant strain causing HCPS. Most exposures are linked to activities that bring individuals into contact with rodent habitats, such as farming, cleaning barns or sheds, camping, or engaging in outdoor recreational activities in rural or semi-rural areas. The sporadic nature of cases, often occurring as isolated incidents rather than outbreaks, makes early recognition challenging. The peak incidence often aligns with agricultural cycles or periods when people are more likely to encounter rodents. Public health surveillance is crucial for identifying clusters and informing targeted prevention strategies, which primarily involve rodent control and personal protective measures in potentially contaminated environments.
The Unique Case of Andes Virus
A particularly noteworthy strain, the Andes virus, found primarily in South America (Chile and Argentina), stands apart due to its documented ability to spread from person to person. This is an unusual characteristic for hantaviruses, which are almost exclusively zoonotic. Person-to-person transmission of Andes virus has been observed during close contact with infected individuals, typically within households or healthcare settings, elevating its public health significance and necessitating heightened IPAC protocols when suspected. This unique transmission pathway underscores the potential for some zoonotic viruses to adapt and pose new challenges.
Clinical Presentation: HCPS vs. HFRS
The clinical course of hantavirus infections varies significantly depending on the viral strain and the resulting syndrome.
- Hantavirus Cardiopulmonary Syndrome (HCPS): Following an incubation period typically ranging from two to four weeks (but potentially as short as a few days to as long as eight weeks), HCPS begins with a prodromal phase characterized by fever (often above 38°C), myalgia (especially in the back and thighs), headache, chills, and gastrointestinal symptoms such as abdominal pain, nausea, vomiting, and diarrhea. This non-specific phase can last for several days before rapidly progressing to the cardiopulmonary phase. Patients develop a sudden onset of cough, dyspnea, and tachypnea, progressing rapidly to non-cardiogenic pulmonary edema, hypoxemia, and severe respiratory distress. This can lead to hypotension and cardiogenic shock, with a fatality rate ranging from 30% to 50%, even with aggressive supportive care.
- Hemorrhagic Fever with Renal Syndrome (HFRS): Predominant in Europe and Asia, HFRS also starts with a febrile phase, accompanied by severe headache, backache, and abdominal pain. This is followed by a hypotensive phase, often with flushing of the face and neck, and petechiae (small red spots from bleeding under the skin), particularly in the axillae and on the palate. The subsequent oliguric phase is marked by acute kidney injury, which can be severe enough to require dialysis. A diuretic phase follows, leading to recovery in most cases, though complications like pulmonary edema or shock can occur. The fatality rate for HFRS varies considerably by strain, from less than 1% for Puumala virus to up to 15% for Hantaan virus.
Diagnosis and Treatment
Diagnosis of hantavirus infection relies on a combination of clinical suspicion, epidemiological context, and laboratory confirmation. Serological tests, detecting IgM and IgG antibodies against hantavirus antigens, are the primary diagnostic tools. Polymerase chain reaction (PCR) testing can detect viral RNA in blood or tissue samples, particularly in the early stages of illness. These specialized tests are performed by reference laboratories such as the National Microbiology Laboratory in Winnipeg, Canada, which plays a crucial role in national surveillance and diagnostic support.
Currently, there is no approved antiviral medication or vaccine specifically for hantavirus infections. Treatment for both HCPS and HFRS is primarily supportive. For HCPS, this involves aggressive management of respiratory failure, often requiring mechanical ventilation, oxygen therapy, and careful fluid management to avoid exacerbating pulmonary edema. Vasopressors may be needed to manage hypotension and shock. For HFRS, supportive care focuses on managing fluid and electrolyte balance, blood pressure, and renal function, which may include dialysis in severe cases. Ribavirin, an antiviral drug, has shown some efficacy in reducing mortality for certain HFRS strains if administered early, but its benefit for HCPS has not been consistently demonstrated.
Infection Prevention and Control for Hantavirus
Given the lack of specific treatments, IPAC measures are critical, especially for the Andes virus. Suspected Andes virus infections mandate strict isolation precautions, including airborne, droplet, and contact precautions, to prevent human-to-human transmission. This typically involves placing the patient in a negative-pressure room, healthcare workers wearing N95 respirators, eye protection, gowns, and gloves. Early involvement of infectious disease specialists in patient management and immediate notification of public health authorities are essential for rapid investigation, contact tracing, and implementation of broader public health interventions. For other hantaviruses, prevention focuses on rodent control: sealing entry points to buildings, eliminating food sources, safely cleaning up rodent droppings (using wet methods and bleach solutions to prevent aerosolization), and wearing appropriate personal protective equipment (PPE) like gloves and respirators when working in rodent-infested areas.
Ebola Virus Disease: A Persistent Global Health Challenge
Ebola virus disease (EVD), caused by viruses of the Filoviridae family, is one of the most severe and deadly viral hemorrhagic fevers. First identified in 1976 during two simultaneous outbreaks in Sudan and near the Ebola River in what is now the Democratic Republic of Congo (DRC), EVD has since caused periodic outbreaks, primarily in Central and West Africa. Researchers widely believe that fruit bats (family Pteropodidae) serve as the natural reservoir for Ebola viruses, with spillover events to humans occurring through contact with infected bats or other infected wild animals (e.g., chimpanzees, gorillas, monkeys, forest antelope, porcupines) found ill or dead in the rainforest.
Transmission Dynamics and Viral Strains
Ebola virus spreads through direct contact with the blood, secretions, organs, or other bodily fluids (such as vomit, diarrhea, urine, saliva, sweat, semen, breast milk) of infected symptomatic people or cadavers. It can also be transmitted through contact with objects and surfaces contaminated with these fluids. Healthcare workers are particularly at risk if appropriate IPAC measures are not rigorously followed. Traditional burial practices that involve close contact with the deceased can also facilitate transmission. It is crucial to note that Ebola is not typically airborne, unlike diseases such as measles or tuberculosis.
There are six known species of Ebola virus, three of which are primarily responsible for human outbreaks: Zaire ebolavirus, Sudan ebolavirus, and Bundibugyo ebolavirus. The Zaire ebolavirus is historically the most lethal and has caused the largest outbreaks, including the devastating 2014-2016 West Africa epidemic.
A Timeline of Major Ebola Outbreaks
- 1976: First identified outbreaks in Zaire (now DRC) and Sudan. The Zaire outbreak near the Ebola River recorded a fatality rate of 88%.
- 1995: Kikwit, Zaire, outbreak (Zaire ebolavirus), with 315 cases and 250 deaths (79% fatality rate).
- 2000-2001: Gulu, Uganda, outbreak (Sudan ebolavirus), 425 cases, 224 deaths (53% fatality rate).
- 2014-2016 West Africa Outbreak: The largest and most complex EVD outbreak to date, primarily affecting Guinea, Liberia, and Sierra Leone. Caused by Zaire ebolavirus, it resulted in over 28,000 cases and more than 11,300 deaths. This outbreak highlighted significant gaps in global health preparedness and response.
- 2018-2020 North Kivu, Ituri, and North Kivu outbreaks, DRC: A prolonged and challenging outbreak in conflict-affected regions of the DRC, caused by Zaire ebolavirus. Despite significant challenges, this outbreak saw the first widespread use of an experimental vaccine and therapeutics.
- Current Outbreaks: The Democratic Republic of Congo has faced numerous EVD outbreaks, including recent ones. The strain currently attracting attention involves Bundibugyo ebolavirus, which typically has a reported fatality rate ranging from 30% to 50%. The persistence of outbreaks underscores the need for continuous vigilance and robust public health infrastructure in affected regions.
Clinical Features and Diagnosis of EVD
The incubation period for EVD ranges from 2 to 21 days, with an average of 8-10 days. Initial symptoms are non-specific and can mimic other common tropical diseases, making early diagnosis challenging. They typically include a sudden onset of fever (38°C or higher), intense weakness (fatigue), muscle pain (myalgia), headache, and sore throat. These are often followed by vomiting, diarrhea, rash, impaired kidney and liver function, and in some cases, both internal and external bleeding (hemorrhage). It is important to emphasize that while EVD is often associated with severe bleeding, hemorrhagic symptoms are not universally present and occur in fewer than half of all patients.
Diagnosis is confirmed through laboratory testing, primarily using reverse transcription polymerase chain reaction (RT-PCR) to detect viral RNA in blood samples. Other diagnostic methods include antigen-capture enzyme-linked immunosorbent assay (ELISA), IgM and IgG antibody tests, and virus isolation. Early and accurate diagnosis is critical for initiating prompt IPAC measures and appropriate patient care.
Screening and Exposure Risks
Due to the severity of EVD and its potential for rapid spread, comprehensive screening and evaluation protocols are essential for individuals presenting with compatible symptoms and possible exposure risks. This includes travelers who have recently visited countries experiencing EVD outbreaks, individuals who have had close contact with confirmed or suspected EVD cases, and those who have handled bats, primates, or game animals from affected regions. Public health authorities issue travel advisories and recommendations based on the epidemiological situation in outbreak zones.
Advances and Limitations in Ebola Treatment
Significant strides have been made in the prevention and treatment of certain forms of EVD, particularly those caused by Zaire ebolavirus.
- Vaccines: The rVSV-ZEBOV vaccine (marketed as Ervebo), targeting Zaire ebolavirus, has proven highly effective. Developed during the West Africa outbreak and subsequently deployed in ring vaccination strategies in the DRC, it received regulatory approval in 2019 and has been instrumental in controlling outbreaks. A second vaccine, Ad26.ZEBOV/MVA-BN-Filo, has also been approved.
- Therapeutics: Two monoclonal antibody treatments, Inmazeb (atoltivimab/maftivimab/odesivimab) and Ebanga (ansuvimab), have been approved for treating Zaire ebolavirus infection. Clinical trials have demonstrated their ability to significantly reduce mortality rates, from approximately 50% to as low as 6-35% when administered early in the disease course. These breakthroughs represent a paradigm shift in EVD management, moving beyond purely supportive care.
However, a critical limitation exists: these approved vaccines and treatments are specific to Zaire ebolavirus. Currently, there are no approved vaccines or specific antiviral medications available to prevent or treat infections caused by other Ebola virus species, such as Bundibugyo ebolavirus or Sudan ebolavirus. For patients infected with these strains, supportive care remains the cornerstone of treatment. This includes aggressive fluid and electrolyte management, maintenance of blood pressure and oxygen status, treatment of secondary infections, and pain management. The lack of strain-specific countermeasures highlights an ongoing research and development gap in global health security.
Rigorous Infection Prevention and Control for EVD
Suspected and confirmed EVD cases necessitate the most rigorous infection prevention and control procedures. Health Canada, alongside international bodies like the WHO and CDC, recommends detailed screening and assessment protocols, alongside extensive personal protective equipment (PPE) for healthcare workers. This typically includes a fit-tested N95 respirator (or higher-level respiratory protection), a full-face shield or goggles, double gloves, fluid-impermeable gowns or coveralls, and boot covers. Strict adherence to donning and doffing procedures, hand hygiene, environmental disinfection, and safe waste management are paramount to preventing nosocomial transmission. Isolation facilities with specialized biosafety measures are often utilized for patient care. Safe and dignified burial practices, which minimize contact with the deceased, are also crucial community-level IPAC interventions.
Broader Implications for Global Health Security
The renewed attention to both hantavirus and Ebola virus disease serves as a potent reminder of several critical aspects of global health security. Firstly, it underscores the persistent threat of zoonotic spillover events, driven by factors such as ecological changes, human encroachment into natural habitats, and increased global travel. Secondly, the initial non-specific symptoms of both diseases highlight the universal challenge of early detection and differential diagnosis, particularly in resource-limited settings or where exotic diseases are not routinely encountered.
The disparity in available treatments and vaccines between different Ebola strains, and the complete absence of specific therapies for hantavirus, illustrates the uneven progress in infectious disease research and development. This calls for sustained investment in broad-spectrum antivirals, platform vaccine technologies, and rapid diagnostic tools that can be adapted quickly to emerging threats.
Finally, the emphasis on strict IPAC measures for both diseases underscores the foundational role of strong public health infrastructure, trained healthcare workforces, and effective risk communication strategies. Public health authorities, medical journals like CMAJ, and international organizations continue to play a vital role in educating professionals and the public, promoting preparedness, and coordinating responses to these enduring public health challenges. The lessons learned from past outbreaks of Ebola, and the ongoing vigilance against hantavirus, inform a proactive approach to infectious disease management, aiming to prevent localized threats from escalating into broader health crises.
