dr. O'Neil here would you like to learn a trick to get an extra couple of days off of work watch this video to find out how let's talk about the periods or stages of disease so as you can see here almost all diseases are going to follow this five-step process now it's not always gonna be a beautiful looking bell curve like this but let's go through each step and we'll give you some examples so first on the far left here we have the incubation period this is a period of time when you were in you're infected but you don't have a disease so you've been colonized by an organism it's increasing in number but you're not actually sick yet so this could be as short as a few hours for something like cholera it can be maybe a day or two for the common cold two or three days for influenza five years for leprosy up to 10 years for HIV so this incubation period can be very very long or very very short but during this period of time you've been infected but you don't have a disease but disease is actually when your body has having trouble maintaining homeostasis so you're gonna have signs or symptoms so incubation period just remember infected no disease the prodromal period is where you're gonna have my old signs or symptoms maybe you're just kind of tired like personally I know that if I get a couple good night's sleep and I'm still tired I know my body's fighting something maybe it's the tickle in your throat these types of things tell you that you're on the way to the period of illness it doesn't mean that you can't stop it and can't get better but that's where you are in these stages the period of illness is when you're getting very very sick you now have a disease you're as sick as you're going to get the period of decline you're still very sick but you're getting better you can tell that you've turned a corner and then we have the period of convalescence so convalescence basically means regaining your strength so you're feeling quite a bit better but you're still tired you're still wore out so one very important thing to remember here is that you can actually spread this disease during any of these periods so of course if you're super super sick right in the middle here the period of illness - the period of decline you're probably more likely to spread the disease but during the incubation period and the period of convalescence you can still spread the disease so that technically means that you can spread a disease before you're sick and after you're sick so feel free to try calling your boss and saying you know I really feel like I'm going to be sick in a day or two so I should probably stay home and rest or call your boss and say I'm feeling better around 99 percent better but I need to convalesce I need to regain my strength and see how that works for you all right you know more go be more go change the world you [Music]