The spread of gene drives in Aedes aegypti is mainly held back by the emergence of resistance alleles, fitness costs to the mosquito, and limited mosquito movement between populations. Resistance can block the gene drive mechanism, while fitness costs may reduce survival or reproduction, making it harder for the drive to persist. Also, since Aedes aegypti populations are often localized, the spread is naturally slower.

In contrast, Wolbachia spreads through maternal transmission and relies on cytoplasmic incompatibility to invade populations. It tends to be more stable once established and generally has lower or context-specific fitness costs. While gene drives can spread traits more rapidly, they are more vulnerable to resistance and instability. Wolbachia moves slower but offers long-term persistence with fewer evolutionary hurdles.