Itching bites may limit Ross River virus infection

To the Editor: Dugdale recently suggested that people who develop skin reactions to mosquito bites may be protected against Ross River virus (RRV) disease.1 He noted that seven patients with a history of RRV disease all reported no skin reaction to mosquito bites, and 18 patients with no past history of RRV disease reported reacting to such bites. We argue that this correlation is entirely to be expected, as the lack of reaction to mosquito bites illustrates that the individuals have been previously exposed to many bites. At least two studies have shown a clear inverse correlation between mosquito exposure and bite reactions.2,3 Clearly, exposure to a large number of mosquito bites increases the risk of infection.4 Thus, a reaction to mosquito bites probably does not protect against RRV disease, but is simply a marker for low exposure to mosquito bites and therefore low risk of RRV infection.