Infectious diseases such as influenza attack the respiratory system - the nose, throat, and lungs. A stomach virus that causes diarrhea and vomiting is not the same as influenza, commonly known as the flu. In most cases, flu symptoms resolve on their own. There are times, however, when influenza and its complications can prove highly serious. Young children aged 5 and younger, especially those under 6 months old, or older adults aged 65 and older are among those at high risk of serious flu-related complications. Residents of long-term care facilities such as nursing homes, individuals with weakened immune systems, and pregnant or recently pregnant women are at high risk of complications. The flu may also disproportionately pose risk to those with previously existing chronic conditions like kidney disease, heart disease, asthma, diabetes, and liver disease, or those who are obese. There are a number of factors that increase the risk of contracting influenza in the first place. Seasonal influenza tends to target seniors and young children, and those in certain working or living conditions such as those leading to being in close proximity with others. Weakened immune systems, chronic illnesses, and pregnancies, also increased the risk of contracting influenza.