 however, it is believed that viruses with very high mutation rates are able to rapidly adapt to new hosts and thereby overcome host-specific immunological defenses, allowing their continued transmission.
<clarity>  however, it is believed that viruses with very high mutation rates are able to rapidly adapt to new hosts and thereby overcome host-specific immunological defenses, allowing their continued transmission.
 however, it is believed that viruses with high mutation rates are able to rapidly adapt to new hosts and thereby overcome host-specific immunological defenses, allowing their continued transmission.