Multistate Outbreak of Seoul Virus: Implications for the One Health Movement and Pandemic Preparedness

(See the Major Article by Knust et al, on pages 1311–9.)

The One Health movement recognizes the inherent interconnection between humans, animals and their shared environment. The first historical references to the One Health concept date to Rudolph Virchow in mid-1800s Germany, with the quotation: “Between animal and human medicine there is no dividing line—nor should there be. The object is different, but the experience obtained constitutes the basis of all medicine” [1]. Today, evidence suggests that >60% of emerging infectious diseases are zoonotic in origin, and emerging, epidemic, and endemic zoonoses cause a tremendous burden of disease, death, and economic hardship across the globe [2, 3].

In this issue of The Journal of Infectious Diseases, Knust and colleagues [4] describe a multistate outbreak investigation of Seoul virus (SEOV) infections among humans and rats. SEOV is a globally endemic Old World member of the Orthohantavirus genus; however, zoonotic infections among humans were rarely reported in the United States before 2017 [5]. The outbreak spanned 11 states, and extensive trace-forward and trace-backward investigations were conducted to assess spread between home-based ratteries, local pet stores, and personal homes. Extensive laboratory testing, including immunoglobulin (Ig) G and IgM serology, traditional and novel quantitative reverse-transcription polymerase chain reaction, and whole-genome sequencing, was conducted on human and rodent samples; whole-genome sequencing results were used for phylogenetic analysis.

Knust et al [4] found evidence of 31 facilities with infected rats or people, and 17 people with evidence of recent SEOV infection. Notably, this is the first description of SEOV in pet rats in the United States, which had previously only been described in wild Norway rats. Serologic analysis suggested a recent introduction of the virus into the pet rat population, because most infected persons had IgM antibodies, implying recent SEOV exposure (<6 months) despite longer durations of rat contact. Although infections with SEOV are described as hemorrhagic fever with renal syndrome, and the mortality rate is estimated at approximately 2%, the majority of case patients identified through this investigation (10 of 17; 59%) were asymptomatic. Among the 7 (41%) with acute symptoms, only 3 required hospitalization, and all recovered with supportive care.

In this outbreak, virus transmission was largely centered among home-based pet rat breeding operations, with complex and difficult-to-document distribution networks, including households with pet rats, small pet stores, and sales via the internet. The authors recommend that rattery owners can reduce the risk of SEOV infection by implementing comprehensive biosecurity measures, such as quarantine and serologic testing of new animals before comingling, cohorting animal groups, regular cleaning and disinfection of enclosures, and systematic record keeping. These and other biosecurity recommendations are not unique to rat owners and SEOV risk but are widely applicable to many other domestic human-animal interactions.

In recent decades, an increasing number of live poultry–associated salmonellosis outbreaks have been identified in the United States, associated with backyard poultry flocks [6]. From 1990 to 2014, 53 such outbreaks were recorded, with 2630 associated illnesses, 387 hospitalizations, and 5 deaths; most human-animal contact occurred in patients’ homes. In 2018, an outbreak of multidrug-resistant Campylobacter jejuni caused 118 cases of illness in 18 states and was linked to puppies sold through the commercial dog industry [7]. These, and many other examples, demonstrate that the risk of zoonotic disease acquisition is not limited to wildlife exposures and international travel. Zoonotic disease risks from domestic animals traditionally kept as pets and nontraditional pets are increasingly described within the United States.

More broadly, this report highlights the importance of a comprehensive One Health approach to health security and outbreak preparedness and response, both domestically and globally. Recent initiates have made advances in formalizing this approach. Globally, the Food and Agriculture Organization, the World Organization for Animal Health, and the World Health Organization have established a tripartite memorandum of understanding, renewed for 2017–2020, committing to multisectoral cooperation on disease risks at the human-animal-environment interface [8]. There is also a growing emphasis on One Health concepts through the Global Health Security Agenda (specifically the Global Health Security Agenda Zoonotic Disease Action Package) and the International Health Regulations [9, 10]. In the United States, a bipartisan bill, the “Advancing Emergency Preparedness Through One Health Act of 2019,” was introduced in the 116th Congress to implement a coordinated One Health approach to better prevent, prepare for, and respond to zoonotic disease outbreaks, and establish a national One Health Framework under a One Health Program [11].

Despite these important steps, the ongoing coronavirus disease 2019 (COVID-19) pandemic has illustrated the critical need for even more intentional work in this area. As with severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome, evidence suggests a bat origin of the SARS–coronavirus 2 (CoV-2), with a possible reservoir host [12–14]. Emerging data suggest that SARS-CoV-2 can infect a variety of animal species, including tigers, mink, and domesticated cats and dogs, with evidence of transmission both from animals to humans and from humans to animals [15–19]. Although ongoing zoonotic transmission is unlikely to be a substantial contributing factor to continuing community spread of SARS-CoV-2, it is an important feature that must be acknowledged and understood.

The COVID-19 pandemic has demonstrated the devastating impact that a zoonotic infection can have on the global community, in terms of both human disease and death, as well as economic devastation. The ongoing global response has reemphasized the need for a definitive One Health approach to pandemic preparedness and response to effectively detect and rapidly respond to threats to human or animal health. It is clear, however, that additional collaborative efforts are needed to implement more effective downstream response and upstream preparedness and prevention measures. In the United States, formalization of a national One Health Program and integration with established or fledgling state and local One Health initiatives is crucial for effective early detection and response efforts. As clearly summarized by McCloskey et al[20], “a one health approach could, with sufficient goodwill, trust, and political support, substantially improve the situation and reduce the threat from future incidents.”

The multistate outbreak investigation described by Knust and colleagues [4] reiterates the ongoing, and often undetected, threat of rare or emerging zoonotic pathogens among humans and animals in the United States. In this instance, astute clinicians elicited a history of rodent exposure in the index case, leading to hantavirus testing and a rapid and robust public health response. This and other aspects of the investigation highlight the importance of a collaborative One Health approach to many emerging, epidemic, and endemic public health threats. Engagement between experts in human, animal, and environmental health within academia, government, and industry at the local, national, and international levels is fundamental to build essential knowledge and partnerships. Whether it is SEOV in ratteries, Campylobacter in puppies, or the current COVID-19 pandemic, a multidisciplinary One Health approach to health security will ensure more comprehensive, collaborative, and coordinated pandemic preparedness and response efforts in communities across the globe.

Note

Potential conflicts of interest. Author certifies no potential conflicts of interest. The author has submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed.

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