Ebola: Does the Route of Infection Influence Disease Severity?

By Ana Espino | Published on June 15, 2026 | 4 min read

Since its discovery in 1976, the Ebola virus has remained one of the most feared infectious agents in the world. Responsible for Ebola virus disease (EVD), it causes a severe hemorrhagic fever that can progress to multiple organ failure and death. Despite recent advances in the development of vaccines and treatments, many questions remain regarding the precise mechanisms of infection and the evaluation of medical countermeasures.

Most current knowledge is based on animal studies. Historically, researchers infected animals through so-called “artificial” routes, particularly intramuscular or intraperitoneal injection, in order to precisely control the administered dose. In humans, however, infection generally occurs through contact between mucous membranes or broken skin and infected biological fluids. These differences raise an important question: does the route of infection influence disease progression? To address this, American researchers reviewed the main animal models used in Ebola virus research and compared the consequences of different routes of infection.


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When the Route of Exposure Changes Disease Progression

The authors analyzed data obtained in several animal species, including nonhuman primates, mice, hamsters, guinea pigs, and ferrets. They compared infections induced through artificial routes, such as intramuscular or intraperitoneal injection, with those produced through routes that more closely resemble natural transmission, including nasal, oral, ocular, and aerosol exposure.

The findings show that the route of infection strongly influences disease progression. In models using intramuscular injection, clinical signs appear rapidly and the disease course is generally more abrupt. By contrast, mucosal exposure often leads to a slower progression, with a longer delay before symptom onset and death. This prolonged course more closely resembles what is observed in human patients.

Researchers also identified differences in the organs affected. Mucosal infections are more commonly associated with pulmonary and gastrointestinal lesions, whereas some artificial routes cause more pronounced liver involvement. In nonhuman primates, guinea pigs, and ferrets, intranasal exposure is notably associated with significant lung involvement and earlier viral shedding, potentially facilitating virus transmission.

The review also confirms that nonhuman primates remain the reference model for accurately reproducing human disease. However, ferrets appear to be a particularly promising alternative, as they develop severe disease after infection with wild-type Ebola virus without requiring prior viral adaptation.


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Toward Models That Better Reflect Human Reality?

This review highlights that the route of exposure is a key determinant in the study of Ebola virus disease. Models based on mucosal infection appear to reproduce more faithfully the timing, clinical manifestations, and transmission mechanisms observed in humans.

However, the authors note that these models also have limitations. Natural-route infections often result in more variable mortality and are more dependent on the viral dose administered, which can complicate the evaluation of new treatments or vaccines. Conversely, artificial routes produce more consistent outcomes and facilitate preclinical studies.

Despite these constraints, the increasing use of models that reproduce natural transmission routes could improve understanding of disease mechanisms and help investigate phenomena that remain poorly understood, such as long-term sequelae and viral persistence in survivors. This represents an important step toward improving future strategies for the prevention and management of Ebola virus disease.


About the author – Ana Espino
PhD in Immunology, specialized in Virology  
As a scientific writer, Ana is passionate about bridging the gap between research and real-world impact. With expertise in immunology, virology, oncology, and clinical studies, she makes complex science clear and accessible. Her mission: to accelerate knowledge sharing and empower evidence-based decisions.