Figure 1.

The immune response against zoonotic viruses in natural reservoirs compared to humans. Top: Zoonotic viruses can directly pass from natural hosts (e.g. bats, mice, monkeys) to humans, or be transmitted through intermediate hosts or vectors (e.g. mosquitoes, cattle). Middle and bottom: Some natural reservoirs have evolved enhanced interferon responses while reducing pro-inflammatory mediators. Increased NKR complexity and diversity, and improved NK cell responsiveness may also contribute to viral persistence while keeping the host asymptomatic. When zoonotic viruses jump to novel hosts such as humans, a slower interferon response and impaired early NK cell activation may lead to poor virus clearance, aberrant immune responses, heighten inflammation, and profound pathology.