Why viruses sometimes disperse in groups?^†.

Area of Science:

• Virology
• Evolutionary Biology
• Microbiology

Background:

• Organismal group dispersal is common, but viral collective spread is understudied.
• Collective viral units deliver multiple genome copies, promoting co-infections.
• Mechanisms include virion aggregation, lipid vesicle cloaking, protein matrices, cell surface binding, and cell-to-cell spread.

Purpose of the Study:

• To investigate the selective advantages of collective viral dispersal.
• To understand the trade-offs between short-term benefits and long-term costs of group spread.
• To clarify the implications of collective dispersal for viral fitness, pathogenicity, and evolution.

Main Methods:

• Review of recent findings on collective viral infectious units.
• Analysis of potential benefits: overcoming antiviral responses, preventing stochastic loss, complementing defects.
• Consideration of costs: mutation accumulation, evolution of cheater viruses, dependence on genetic relatedness.

Main Results:

• Collective dispersal offers potential advantages like shared transmission vehicles and enhanced infection establishment.
• Group spread can overwhelm host defenses and compensate for viral genome defects.
• Potential long-term disadvantages include increased mutation rates and the rise of defective or cheating viral strains.

Conclusions:

• The fitness consequences of collective viral dispersal depend on the balance of costs and benefits.
• Genetic relatedness among viruses within a collective unit influences these costs and benefits.
• Further research, including controlled experiments, is needed to fully elucidate the evolutionary implications of collective viral spread.