Health and medicine
- What is the flu?
- Catching and spreading the flu
- When flu viruses attack!
- Three types of flu
- Naming the flu: H-something, N-something
- Testing for the flu
- Antiviral drugs for the flu
- Genetic shift in flu
- Flu vaccine efficacy
- Flu shift and drift
- Two flu vaccines (TIV and LAIV)
- Flu vaccine risks and benefits
- Making flu vaccine each year
- 5 common flu vaccine excuses
- Vaccines and the autism myth - part 1
- Vaccines and the autism myth - part 2
- Flu surveillance
Find out how many people get hospitalized and die from the flu each year, and learn how we can use the internet to keep tabs on the flu! Rishi is a pediatric infectious disease physician and works at Khan Academy. These videos do not provide medical advice and are for informational purposes only. The videos are not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read or seen in any Khan Academy video. Created by Rishi Desai.
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- I'm not saying that deaths from flu are inconsequential, but what percentage of the population is that? And to compare, what are the numbers for death from cancer, heart attacks, HIV, car wrecks?(12 votes)
- The percentage is irrelevant when a simple preventative measure has been shown time and again to prevent far more deaths related to flu than any possible risk associated with getting the shot. It would be really nice if we had such an effective preventative measure for cancer and heart attacks because as you note, the death toll from those is immense.
From John Donne:
No man is an island entire of itself; every man
is a piece of the continent, a part of the main;
if a clod be washed away by the sea, Europe
is the less, as well as if a promontory were, as
well as any manner of thy friends or of thine
own were; any man's death diminishes me,
because I am involved in mankind.
And therefore never send to know for whom
the bell tolls; it tolls for thee.
And if you like Hemingway, now you know where the title of one of his novels came from.(3 votes)
- So how does the flu kill someone? Isn't it just a sickness, like the cold?(3 votes)
- The viral infection that is the flu isn't the dangerous part of the sickness. The body's immune-system is weakened due to fighting the virus, allowing secondary bacterial infections to enter the body, reproduce and causing other more lethal complications such as encephalitis or pneumonia.(7 votes)
- Usually people who search their symptoms up on Google do it many times at different times. Sometimes people don't search symptoms on Google. What about the people who dont search up flu things on the computer. How is google supposed to have accurate data with all of these variables?(2 votes)
- The actual numbers are much less important than the trend. The strong correlation between hospitalised flu cases and increased Google searches suggests that search data may be useful for detecting outbreaks where no (or few) cases require hospitalisation.(6 votes)
- Is it just coincidence that the Google data matches perfectly with the CDC data? It rather mind boggling that such an idea would work, because there is no concrete relation that the total number of searches is related to the total number of hospital cases(considering flu searches equal to the flu cases in hospitals)(1 vote)
- They're plotting different information, but the relationship is (probably) not just coincidental. If you imagine that a percentage of people with the flu will be sick enough to be hospitalised, you'd expect that a bigger percentage will be sick outside hospitals.
It's not unreasonable to expect those figures to line up, but it's important to test those kinds of assumptions. The similarities in the timeline are important, as is the proportional change in the magnitudes (rather than the absolute magnitudes). By itself it's kind of interesting, but it suggests a possible method for the use of hospital case load data to come up with a more reliable estimate for the numbers of non-hospitalised flu cases. And if the method is valid for flu cases, it may also be valid for epidemiological monitoring of other conditions.(6 votes)
- What about the winter season makes the flu more prevalent. Obviously it has something to do with the weather but what is the reason for this? Does cold suppress the immune system? I thought viruses and bacteria don't do as well in cold weather as they do in warmer temperatures.(2 votes)
- from a December 2007 New York Times article about this exact question:
"The answer, [researchers now] say, has to do with the virus itself. It is more stable and stays in the air longer when air is cold and dry, the exact conditions for much of the flu season.
'Influenza virus is more likely to be transmitted during winter on the way to the subway than in a warm room,' said Peter Palese, a flu researcher who is professor and chairman of the microbiology department at Mount Sinai School of Medicine in New York and the lead author of the flu study."
- where was central america, china and part of africa? at the global map(3 votes)
- John Lee, can you say something useful? BTW Julian, i don't know the answer :\(1 vote)
- i hear there are other deadly flus. what are they called?(2 votes)
- There are a variety of flu viruses. They often change or mutate and if your body cannot recognize a disease as a threat, either a) the virus effects the body worse because the body cannot figure out what it is fighting or b) the body overreacts to the the intruder and takes crazy measures to fight back. The body literally burns itself out fighting the disease. This is the reason that a lot of heathy people died in strange ways in the 1918 flu pandemic. Men and women at their prime died because their bodies overreacted. Flu can also be deadly to people with a preexisting condition such as HIV/AIDS or the very old and very young. It is still called flu, but it could be deadlier than other strains.(2 votes)
- What if you have all of the flu symptoms, is that bad?(1 vote)
- While having "all of the flu" symptoms aren't bad, those who are very young, very old, or immunocompromised are at greater risk from becoming dehydrated, malnourished, and unable to manage other symptoms. These people should have a lower threshold for seeking medical attention. Most healthy individuals will bounce back in a few days.(3 votes)
- why in winter people tend to be more easy to get flu ?? is it something that viruses are more stable in low temperature ? and what about "common cold"'s ? or what about bacteria cold ?(2 votes)
- How can more people die of flu in the US then of AIDS?(1 vote)
- AIDS isn't transmissible by air like the flu is so the number of people who are infected by it every year is very small. As a result the number of people who die from it every year is also small. The flu infects a large number of people every year. Not everyone with the flu dies but enough do that it makes the flu a major killer of people.(3 votes)
Let's take a step back and think about the entire planet-- the planet we live on, Earth. We've got lots of little continents and water, right? I'm going to draw that out here. And, if I was to ask you, how much flu affects this planet-- all the people that inhabit this planet-- in one year, probably the best place to go to answer that question would be the WHO. And that's exactly what I did. I went to the World Health Organization, and I wanted to know how many people on our planet, Earth, in one year-- let me write that out here so we know that we're not talking about many, many years, just one year-- how many people are hospitalized from the flu? So this is actually a pretty mind-numbing number. Look at this huge number, 5 million-- 3 million to 5 million-- end up going to the hospital, because they have severe complications of flu. This could be anything from like, pneumonia to bronchitis, to having a horrible asthma attack, something like that. So this is not how many people get sick with the flu, but how many actually end up in the hospital or have severe disease from influenza. And then, another number I wanted to look up is how many actually die of having the flu? And you know, a lot of people will say, well, you know, the flu is not a big deal. It doesn't really affect you much, and you just get kind of sick. And if that were true, then we wouldn't be having a quarter million to a half a million deaths each year from the flu. This is a really kind of a sad commentary, when you consider the fact that this is something that we actually do have a vaccine for. So in the world, we have a huge number of deaths happening. Now, whenever I hear statistics like this, my mind always kind of takes comfort. Like, I always think, well, I'm living in a developed country, and I have health insurance, and I can go to the doctor if I need to. And so, what are the numbers like in the US? I mean, I'm sure that they're obviously not as high as that. And what I wanted to prove to you is, actually, the numbers are not insignificant. So in the US, we have the CDC. And the Centers for Disease Control tells us that we have about 200,000 people going to the hospital each year because of the flu. Now you have millions of people getting the flu, right? That's another number. But this is just how many people end up going to the hospital because of it. And then this is probably the scariest thing, we have 3,000 to 49,000 people dying of the flu every single year. And I wanted to see why they had such a big range. So I actually looked at the study. And it turns out, between 1976 and 2007, they actually kept track of how many people had died of the flu. And this is not, obviously, an exact graph. But I just wanted to show you that they said, well, one year, the number was as high as 49,000. This is number of people that died because of the flu in the United States. And one year, the number was as low as 3,000. And I say as low as 3,000, but, I mean, 3,000 deaths is still a lot of deaths. So we have thousands of people dying of flu, and we have hundreds of thousands of people going to the hospital for flu. So if someone ever tells you that it's not a serious problem in the US or in developed countries, that is definitely not true. And it's a huge problem internationally. Now I want to show you some interesting data. This actually comes from the CDC. They actually put this on their website, and you can check this out. It's actually pretty neat and helpful to understand exactly how we gather information about flu. So the key word here is surveillance. You see this influenza surveillance report here. And surveillance basically means, how do we gather data around a disease, or gather data around anything, really? So let's talk through that process. The traditional way we do it was we say, OK, we have a person. Let's say this person is me. Let's say I'm feeling pretty lousy from the flu. I've got a case of sore throat, and I've got some runny nose, and maybe I've got some fevers and body aches. So I'm going to go to my doctor. And my doctor is going to be over here, in blue. And my doctor's going to be pretty smart, pretty savvy. And they're going to figure out pretty quickly that I've got the flu. They're smiling because they figured it out. And so, then they're going to take that information, and they're going to say, OK, well, I have a person here by the name of Rishi, and he has the flu. And they're going to send that information where? It's going to go to the hospital that they work in-- or the clinic, let's say. So that clinic now has a record of all the people that walk through and have the flu. So now that clinic or that hospital is going to also take that list of people-- and, you know, it's protected, confidential information, so it may, at this point, not even have your name on it, maybe they just have the total number of people with the flu-- and they're going to send that over, let's say, to the county. And I live in San Francisco. So let's say this is San Francisco County. So they send that information to my county, San Francisco County. And then, that county is going to get that information. They're going to say, well, thank you, hospital, for sending it over. And they're going to take that whole list, and they're going to add it to all the other hospitals that sent them information. And they're going to get a bigger number. And they're going to get that bigger number, and they're going to send it to the state of California. The state of California gathers information about the flu. And they're going to say, thank you so much, county, for sending it over. This is California. And California is going to gather up all the information about who's got flu in their entire state-- all the different counties that send them information. And they're going to send that information, finally, to the United States' kind of public health authority, and it's based over here in Atlanta. So eventually that information goes to the Centers for Disease Control. So this is kind of the chain of information that we traditionally use. And that's why, over here, it says, this is estimates reported by the state and territorial epidemiologists, so all the different territories and states that are encompassed by the United States. So that's what that means. And this graph is telling us that we're seeing regional and widespread flu in almost every state at the end of 2012-- so, just a couple weeks ago, since, today, the date is January 10th. Now some really smart people got together, and they said, is this the only way to actually gather information about the flu? Maybe there's another way. So some folks at Google got in touch with some folks at the CDC. And they said, let's put our brains together, and let's figure out if there are other ways that we can actually gather information. Now think about me. Now, I had the flu, right? What else might I do? Well, I might jump on my computer, because I'm a computer kind of guy, and I like to learn about what's going on. And so I might jump on my computer. And I'll say, OK, let me search in Google. Maybe I'll search in Google to find out what I might have. So I'll type into Google and say, hey Google, tell me what I need to worry about. And I'll go through, and I might find that Google tells me that if you type in sore throat-- let's say, I type in the word sore throat here-- it might give me some search results. It'll say, well, maybe you should take this medicine or that medicine. Or I might type in the word cough or fever. These are all words that I might type in the day that I get sick. And I might also go to the hospital, or I might not. Maybe I'm not that sick. So I think, let me just type in these words. And what Google gets is they get all the searches that Rishi did that day, as well as all the searches that other people in my community are doing. So maybe there are other people searching. Maybe Mr. Red is searching, and maybe Mrs. Blue is searching. So maybe all these other people are searching as well for the same kind of words. And what are these words? These are basically all flu searches, right? Kind of searches related to the flu. So I'm going to call them flu searches. And there are many other terms as well, but I'm not listing all of them, just kind of some of them, so you get a sense for what this means. So Google, what they could do is they could actually tally up the total number of searches related to the flu that are happening in a community, let's say in San Francisco, in one day. And that total I'm calling this total right here, flu searches. That's the total searches for flu-related terms in a day out of San Francisco. Now, over here, we've got other searches. So let's say we've got searches for weather in Nepal. Maybe I'm going on a trip to Nepal, or somebody in my community is going, and they search for that. Or maybe someone is searching for basketball news. They want to know which team won and which team lost. They want to know that. And maybe a third person is searching for cell phones. So really, these are all the other kind of searches that are happening on Google. And there are probably thousands and thousands of them. And you could tally all these searches up, and this would be the total searches in Google. And this is, again, the searches happening in one day in one community. This could be all the searches happening in San Francisco. And maybe there's a person over here, a little girl in yellow, and maybe this is a man in purple who's searching, and maybe this is a person in green. And these aren't necessarily different people, right? It could be, maybe Mr. Red searched for sore throat, and then later he was interested in basketball news. So he actually was in both groups. So really, we're not counting people, we're counting total searches. That's the key idea here. Total searches is what matters, in a day, in some community. Now you could actually take these numbers and make some sense out of them. This is where the folks at Google and the folks at the CDC did something very clever. They said, OK, let's put this number here and this number here, and let's divide by them. So let's do flu searches divided by total searches. And if you divide the two, you're going to get some fraction, some percentage. And it's going to be pretty small, because flu searches is going to be a small fraction of the total searches that are happening. And then you could take that fraction-- this is where it gets really interesting-- and you could say, OK, let's look at a whole year. This fraction we got for a given day, but you could do this every single day for a whole year. And you could say, January, February, March, April. You could go through the entire year, the entire calendar. This is June. And let's say July. This is August, September, October, November, December. And if you did this 365 times, you know, each day you did this, let's say, or you could do this weekly, however you want, you would get some fraction, some percent. And maybe the percentages would be small, but you could graph them out if you wanted to. And you'd probably notice something like this-- you'd notice that in the winter months, the numbers get bigger, and in the summer months, the numbers get smaller. Because, in the summertime, fewer people are probably searching for cough, runny nose, things like that, because those things usually happen in the winter. So you might get something like this-- this is percent, over here. So this is kind of a trend that you might see. Now, as I said, the people at the CDC and the people at Google were very clever to think of this. And they actually compared data. They said, OK, let's compare data from Google to CDC data. Let's see how they actually look side-by-side. Here, in my graph, I had done one year. This is one year, from here to here. And you can actually see that this is basically the same thing. This is from January through December. So we're seeing peaks in the wintertime, and that's understandable. But the great thing about this graph is you can see that Google flu trends actually line up really nice with the US data. And the US data, if you look down here, comes from, as we said, the CDC. So this is actually information from the CDC about influenza-like illness. And they're seeing, or we're seeing, that there's a fantastic correlation, both in the timing, because the peaks are happening basically at the same time, and also in the magnitude, so some years are smaller and some years are bigger. So it's actually pretty impressive that the data from searches that are happening on Google actually lines up really well with data, the traditional way that we get data, through surveillance in our public health system. Let me show you one more thing now. So if you look currently-- so the last graph was six years. I just want to quickly point that out. This is six years of data, 2004 to 2009. But, if you look currently, we actually have 20-- and, where's the date here-- 2012 and 2013. And here we are between December and January. In fact, today's date is January 10th, and it's 2013. So here we are, and you can see that the searches are really peaking out. This is looking at national data, but you could also change it. You could say, well, instead of the US, I'd like to look at Mexico, or I'd like to look at Canada, or some other country. Or you could say, instead of looking nationally, I want to look at some city or some state. So you could change it, and this is actually something I encourage you to play with if you're interested. Go to google.org and play around. Check out your own country, your own community, and you could see how many people in your area are searching for flu-related words. And then, finally, if you actually look at the international level, you can actually see the map that's happening internationally, globally. And here some interesting trends also appear. You can see all this activity in the northern hemisphere, and a lot less in the southern hemisphere, which makes sense, because it's our winter season, and flu is definitely a virus that affects us more in the wintertime. And you can see that some countries have really intense levels, like the US, and high levels, like Canada, and some of these countries have more moderate levels, or low levels, like Europe and Russia and Japan.