Are there malaria-infected mosquitoes in North America?
North America is usually defined as including Canada, the United States and Mexico. Of these, Mexico has known regions of regular malaria transmission; specifically the regions bordering Guatemala and Belize in the south (Chiapas, Quintana Roo and Tabasco), rural areas in the tropical lowlands slightly further north (parts of Oaxaca, Nayarit and Sinaloa) and a very localised section of northern Mexico, located across the states of Chihuahua, Sonora and Durango. Travellers to these areas are recommended to take measures to prevent against malaria infection, such as minimising mosquito bites or taking prophylactic medication. Both P. falciparum and P. vivax are known to be transmitted in Mexico, so you should consult with a travel physician before deciding which form of preventative (prophylactic) medication to take, depending on the length of your stay, your budget and the type of malaria most commonly found in the area to which you are travelling.
Malaria was once also widespread in the southern USA, though a concerted public health campaign that started in 1947 (mainly consisting of reducing the number of mosquitoes through insecticide spraying and control of stagnant water bodies) greatly reduced transmission and led to the disease being considered eliminated by the 1950s. Occasionally, small pockets of transmission will be reported, though stringent diagnosis and treatment quickly places these outbreaks under control once more.
However, there are additional cases of malarial mosquitoes occasionally also reported even from northern parts of the United States and Canada; these are when mosquitoes are accidentally transported from malarial regions, for example in airplanes, in luggage or in shipping containers. These mosquitoes almost never transmit the disease to people, and in most temperate regions, do not live long enough to be a public health threat or to enable the persistance of the disease.