CHARLESTON, SC (WCSC) - At their core, the flu and a cold are very similar. Both are respiratory illnesses but are caused by different viruses.
The flu is worse than a cold and tends to have more intense symptoms according to the Center for Disease Control. Someone with a cold is more likely to have a runny nose and it doesn't result in serious health problems.
The onset of symptoms for the flu is usually more abrupt, the CDC says. A fever is often more common with flu patients while its rarer for those with a cold. Headaches also often occur in flu patients while they're not as common for people with a cold.
The flu also tends to make existing medical issues such as asthma worse than normal. Special tests that usually must be done within the first few days of illness can tell if a person has the flu according to the CDC.