The salivary glands of Aedes aegypti were found to be damaged by Semliki Forest virus. A second arbovirus introduced into such mosquitoes replicated, but transmission rates were greatly suppressed.

After a mosquito was first infected with a noncytopathic arbovirus and then with SFV, the glands were not protected from damage. The transmission rate of SFV in these mosquitoes declined to zero as damage progressed, but there was no suppression of transmission of the noncytopathic virus. This continued secretion of virus might be attributable to clusters of histologically normal cells, which can be seen in many sections of damaged salivary glands.