Characteristics of a Pandemic—The Devil is in the Details


What makes a germ more likely to cause a pandemic? A new report poses a novel framework for addressing this question.

Preparing for pandemics is challenging to say the least. There are a multitude of sectors, agencies, professions, and avenues that need to be considered when we work to prevent a pandemic from occurring. Aside from the reality that the United States is just not ready for the next pandemic, especially if it’s influenza, how can we go about strengthening our response?

Global health security programs seek to do this through efforts that range from strengthening laboratory capacity to infection prevention to epidemiological response, and more. Part of this preparedness puzzle is understanding the characteristics of pandemic pathogens. A new report from the Johns Hopkins Center for Health Security (JHCS) took aim at this very issue, asking the question, “What are the characteristics of naturally occurring microorganisms that pose a global catastrophic biological risk (GCBR)?”

The JHCHS sought to bring clarity to the complex and often overwhelming notion of preparing for a GCBR by stepping away from the pathogen list model and establishing a framework that would identify those characteristics likely to result in such an event.

The team established this framework through a review of published biomedical literature and reports on emerging infectious diseases characteristics, interviews with more than 120 technical experts who work across academia, industry, and agencies, and lastly, a pandemic pathogens meeting to discuss their findings and gain additional insight into the assumptions they were making.

Although there are several findings within the report, I'm going to break down some of the key items. Mode of transmission is, of course, vital, and those pathogens that are transmitted through the respiratory route are more likely to lead to pandemic spread. The timing of transmission will also play a key factor and viruses, especially RNA viruses, are most likely to have the capacity to cause a pandemic. Human factors or complex disasters can elevate pathogens to GCBR levels, as issues were identified in hospital preparedness, medical countermeasures, availability of critical workforce, etc. The report authors also note that increasing specific diagnoses of infectious diseases in clinical environments would provide the means to increase our chances of identifying an emerging pathogen with pandemic potential. Especially in light of the limited diagnostic or laboratory capacity that is rampant, as well as the practice of syndromic diagnosis (ie, nonspecific diagnosis of sepsis or pneumonia).

Their recommendations focused on flexibility of an approach, introducing fluidity to the historical pathogen list-based approaches to pandemic preparedness, surveillance of humans with respiratory-borne RNA viruses as a higher priority, etc. Moreover, they underlined the importance of prioritizing RNA respiratory virus vaccines, including a universal flu vaccine, and pursuing microbiologic-specific diagnoses of infectious disease syndromes in all locations as a routine practice.

I had the opportunity to pose some questions to one of the authors of the report, infectious disease physician Amesh Adalja, MD, FIDSA, as I was curious about what he would identify as the most challenging aspect of establishing this framework. He noted that “One of the most challenging aspects of the project was to conceptually distinguish global catastrophic biological risk level pathogens from those that could cause devastating outbreaks that fell below this threshold. For example, the 1918 influenza would be a GCBR-level risk while SARS (2003) and Ebola (2014) are better characterized as pathogens of critical regional importance. It was also challenging to determine what aspects of severe GCBR-level infectious disease outbreaks in other animal species (eg, bats, frogs, salamanders, etc) are applicable to the understanding human GCBR-level threats.”

I was also curious as to what he felt was the most important thing for physicians to take away from this report. Dr. Adalja noted that he hoped that physicians reading the report would gain an appreciation for the power of infectious disease and be much more apt to pursue diagnostic tests that reveal the etiologic agent of an illness and do away with the wastebasket diagnosis of ‘viral syndrome’.

Overall, this report is an important and critical read for all who would play a role in pandemic response or preparedness (which, truly is all of us). The CHS findings pose critical questions as to how we handle global health security and pandemic preparedness, as well as what inherently makes a microorganism likely to cause a pandemic. Moreover, the report speaks to medical providers and those working on the frontline, which is a breath of fresh air for so many of us who are all too often given non-specific guidance that fails to meet the true demands of preparing for pandemics.

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