A type of bacteria that infects many insects may make mosquitoes more resistant to viruses that can be dangerous to humans, researchers have found. The discovery could be helpful in the battles against two painful and sometimes fatal diseases, dengue and chikungunya. Last year, researchers showed they could take Wolbachia bacteria from fruit flies and infect mosquitoes with it, cutting their already brief life spans by half. That discovery was important because most of the malaria transmitted by female mosquitoes is transmitted late in their lives. They must pick up the parasites by biting an infected human, and it takes...