Catching and spreading the flu

So today's January 11, 2013. I'm just going to circle the date on my little calendar here. And let's say I came home from work and I just felt really lousy, just awful. Fevers, sore throat, cough, body aches, you name it. This is the first day I've been feeling like this. And up until now, since the new year started, I was feeling really great. I had no symptoms. I was going to work. Feeling myself. So all these days I was feeling good. And then all of a sudden the 11th hit and I just got, all of a sudden, these symptoms. So I'm already suspecting the flu based on what we know. It started abruptly. I've got the symptoms for it. And a few questions start popping up in my head. The first question I want to know is, when can I expect to start feeling better? That's usually the first thing people want to know. So let's think about what we know about the flu in terms of how long the symptoms usually last. Because that's going to help us predict when I can expect to start feeling myself again. So we know that usually symptoms last for three to seven days. So I'm going to say, OK, all these days I'm going to expect to feel kind of the same maybe. I might start feeling a little bit better by the 16th or 17th. But that would be seven days. So these are the days I can expect to feel kind of lousy. And on average I should start feeling myself again maybe by the 18th and 19th. I should start feeling the way I normally do. So according to this calendar I would start feeling better by January 18. That would be my target date. And this isn't exact. This is just a rough idea. So what's the next thing that people usually try to figure out about the flu? They always want to know, who did they get it from? They always want to figure out who the culprit was. Who gave the flu to them. So I'm no different. I want to know who did I get it from. And so I think back and I say, well, I felt good on the 10th and I felt pretty lousy on the 11th. And your instinct might be to say, well, of course I probably got it on January 10. On Thursday. But, in fact, you have to go a little bit further back. Sometimes you can get it back as far as four days. So I'm going to circle the days that I could've potentially gotten the flu from somebody. And it turns out it could've been any time this week. So I'm going to write that down. So January 7th to January 10th. That's the window in which somebody gave me the flu. Now how do I know that I got it from somebody? Maybe I got it from the doorknob. Or maybe I got it from the remote control that someone was touching. And those kinds of environmental objects, sometimes you can get diseases from there. But with the flu you generally get it from another person. And the reason is, is because you've got this RNA that's protected by an envelope. Remember this green layer here, this double layer, is a lipid or a fat bilayer. It's got two layers of lipid or fat. And this is what we've been calling our envelope. This is the envelope. Now because it's got an envelope it means that the virus is actually more sensitive to the environment. The main way, then, that the influenza virus will get you sick is when you get it directly from another person because this envelope actually makes it very sensitive to the environment. It doesn't really do well when it's out in the environment by itself. So usually you get it directly from somebody. Maybe they cough or they sneeze. Maybe they get it on their hands and they shake your hand. Usually directly from another sick person. So really if I want to know where I got it from I need to brainstorm and think, who did I encounter between January 7 and January 10 that was sick? Now I also want to know, who could I've given the flu to? I'm a conscientious person. I don't want to give the flu to other healthy people if I can avoid it. It turns out you can actually spread the flu-- I'm going to circle it in purple here-- one day before you even have symptoms. So on the 10th of January, this is the day before I was sick, when I was actually feeling really healthy, I could have already been spreading the flu to other people. On that day. On January 10. And of course all these days when I'm sick I could also spread the flu. And that's more intuitive. Because I've got sneezing and coughing and other symptoms. But the interesting one is that on January 10 through the 17 I could have actually spread the flu around. So January 10, which is again a day before my symptoms through the 17th, I could have started spreading the flu. So to know exactly who I gave the flu to I've got a really brainstorm and think well who did I interact with on January 10th. Starting with that date. Well, of course I see my family every day. So family. And I'm a worker, an employee. So my coworkers. I would see them. And there are other folks, too. Like friends. I may, maybe not yet, but perhaps I might have dinner or meet up with some friends. Or I might actually even see some strangers. Sometimes I like to take the bus and I may see some strangers or I might shake someone's hand randomly. And so these are all the different folks who I've got to brainstorm and think about in terms of who I might give the flu to. Or who I might have already given the flu to. Maybe yesterday, January 10. Now let me actually bring up a little bit more canvas. Make some space. And think about these groups of people who I may interact with. In terms of family, for me, my closest family is my fiance. So I live with my fiance and I'm going to draw a picture of my fiance here. And my fiance is generally healthy. And so that's her right there. And then of course there are some other folks. Let's say some coworkers. Maybe I have a coworker-- I'm going to do in a different color-- who is over here also feeling pretty good. And looks healthy. But actually has diabetes, which is an important medical condition. And let's say I have some family friends. I'm going to draw a friend here. Here is my friend. And my friend happens to be pregnant right now. So this is my friend and she is pregnant. Over here. And she's got, of course, then, a little fetus inside of her. So this is my pregnant friend. And my pregnant friend has a two-year-old daughter. So a little two-year-old daughter over here. Two-year-old and my friend herself is pregnant. So I've got my coworker with diabetes. I've got a pregnant friend and a two-year-old daughter. And finally, let me actually go to strangers. Let's say I was actually on the bus. Or maybe I'm going to ride the bus. And here's a stranger on the bus. And this stranger is in a wheelchair. This is a wheelchair here. So this is a stranger who is riding on the bus with me one day and perhaps I help her off. And she thanks me by shaking my hand. So perhaps this elderly lady shakes my hand. And she's a stranger to me, but now I've potentially given her the flu as well. So while I had the flu I actually came into contact with some people that we would consider high risk. I've drawn for you now someone with a comorbidity, which is diabetes, meaning they have some medical condition; someone who is pregnant; a young child; and someone who's very old. And of course over here we have my fiance. And she's healthy and has no medical conditions. But do you think she's going to be too happy if she finds out that I gave her the flu? Probably not. So she's not going to be too happy with me either. So it's really important for me to keep all these different people in mind and know that I don't want to give other people the flu. Especially people that are high risk. These are high risk individuals. So why do we care so much about these high risk individuals? Well, it's because they develop complications of flu. And this is what it really boils down to. You remember we initially talked about all the hundreds of thousands of people in the US and around the world that get hospitalized for the flu. And then the numbers of people that die from the flu. Well, overwhelmingly it's people in this group. This high risk group. And the things that they get, the kind of complications they get, are many. Actually, flu leads to many different types of complications. And I'm going to draw out just a few of them for you. I don't want to give you an exhaustive list. But I want you to at least get an appreciation for the kinds of things we're talking about. So, for example, let's say these are your lungs. I'm drawing two branches of your lungs. And this is going to your left lung and the other branch is going to your right lung. So this is your trachea splitting up. And you know that the flu, the influenza, is going to affect the cells in your respiratory tree. So it's going to affect these cells and it's going to cause inflammation. You're going to get a big immune response. And if that response is really big, let's say you have a big response, and if it's around these airways here, these bronchioles-- let me actually extend this out a little bit, so you can at least appreciate where the arrow's going. If the response is really strong in the bronchioles, we call that bronchitis. So someone might actually develop bronchitis as a result of getting the flu. Now someone else might actually have a big inflammatory reaction in these little air sacs. Your lungs end in thousands and thousands of little air sacs. And if that happens, then you might call that pneumonia. You might say, well, this person has pneumonia. Finally, you have smooth muscle. Actually, lots and lots of it. Smooth muscle that wraps around the bronchioles. And sometimes with the flu you actually can trigger twitichiness of that smooth muscle. It starts spasming. And when that happens we know that sometimes as an asthma attack. So you can actually get an asthma attack related to the flu. So all sorts of things like this can happen. And it's awful. These are things that can actually land you in the hospital. Or can cause death, as well. So these are the kinds of complications. And there are other ones. Things like ear infections and sinus infections and many, many other things as well. But here I just wanted to show you a few of the complications that people get. And show you and remind you that it's usually the high risk people that you have to worry about.