Quantifying viral pandemic potential from experimental transmission studies.

Area of Science:

• Virology
• Epidemiology
• Mathematical Modeling

Background:

• Two major pandemic respiratory viruses, H1N1 and SARS-CoV-2, emerged from animal reservoirs in recent decades.
• Current surveillance for zoonotic viruses faces challenges due to viral diversity and limited tools for pandemic risk assessment.
• Existing methods like in vitro assays and animal transmission studies offer limited resolution for population-level viral dynamics.

Purpose of the Study:

• To develop an analytical framework for quantitative risk assessment of emerging zoonotic viruses.
• To extend the utility of experimental transmission studies for population-level viral dynamic projections.
• To improve the assessment of pandemic risk for viruses with pandemic potential.

Main Methods:

• Developed modeling approaches to estimate transmission parameters and population-level emergence risk.
• Utilized within-host viral titer data from index and contact animals in experimental transmission studies.
• Applied the framework to influenza A virus (IAV) ferret transmission experiments involving H1N1pdm09 and H3N2 strains.

Main Results:

• The H3N2 virus demonstrated lower transmissibility than the H1N1 virus when controlling for viral titers.
• The H1N1 virus exhibited more robust replication in ferrets, resulting in a higher projected reproduction number.
• H1N1 showed a higher projected epidemic growth rate compared to H3N2, indicating a greater likelihood of epidemic spread.

Conclusions:

• The presented analytical framework enables more quantitative risk assessments of emerging viruses.
• Findings suggest H1N1 poses a greater immediate epidemic risk than H3N2 based on transmissibility and replication.
• This approach can enhance the quantitative risk assessment of other viruses of pandemic concern.