The start of West Nile virus transmission in some U.S. states has come earlier than usual, with the highest number of cases in early summer since 2004, according to the U.S. Centers for Disease Control and Prevention (CDC). In response, Delaware has been using sentinel chickens as an early warning system for mosquito-borne diseases, such as West Nile virus and Eastern equine encephalitis (EEE). These chickens are not infected by the viruses they detect but can carry antibodies after being bitten by infected mosquitoes, making them useful for monitoring disease activity. By tracking the presence of these antibodies in the chickens, officials can determine where infected mosquitoes are active and take targeted measures to protect the public. Delaware’s program involves maintaining flocks of four chickens at 20 different locations across the state. The initiative, which started in the early 1980s, is a relatively simple and cost-effective method of monitoring disease trends. While some states have shifted to testing pools of mosquitoes, which can be faster, Delaware continues using chickens because they can detect viruses in areas where mosquito testing might miss them. Chickens also stay in place, giving officials confidence that the infected mosquitoes are active in that specific location. Typically, cases of mosquito-borne viruses like West Nile and EEE begin appearing from north to south as migrating birds pass the viruses to mosquitoes. In Delaware, the season usually starts in early August. The sentinel chickens have also proven useful in detecting new or emerging mosquito-borne illnesses. For example, when West Nile first appeared in Delaware in 2000, officials initially tested dead wild birds but later switched to using the chickens they already had for monitoring. Other states also use similar methods to detect diseases like St. Louis encephalitis. The long-term data collected from sentinel chickens has helped researchers create models to predict the severity of disease seasons. Scientists like Lindsay Campbell, an associate professor at the University of Florida, have used this data along with environmental factors like temperature, rainfall, and bird migration patterns to better understand the conditions that lead to outbreaks. These models can help officials prepare for future risks by identifying patterns that correlate with more or less severe virus seasons. While sentinel chickens show what has already happened, the goal is to use this information to predict future trends and better manage public health responses.