Next, let's think about a specific surveillance system, and through that example, think a bit more about stakeholders in surveillance systems. The surveillance system we're going to talk about today is Japanese encephalitis surveillance in Bangladesh. Let me give you just a brief background on what Japanese encephalitis virus is. It's a vector-borne infection. It's transmitted to humans by mosquitoes. A major vector are Culex mosquitoes, but there are many different species that are competent vectors for Japanese encephalitis. Wading birds and pigs are reservoirs of the virus, so what that means is when a mosquito bites a wading bird or a pig that's infected with the virus, they become infected with the virus and then when they bite humans, they can pass the infection on to humans. Humans are dead-end hosts for Japanese encephalitis. What that means is that humans cannot infect mosquitoes so humans don't serve as a reservoir for continuing infection even though they themselves can and do get infected. The vast majority of people who are infected with Japanese encephalitis virus will never know it. They have asymptomatic infections. Rarely, however, they do develop clinical disease and it can be very severe. It causes brain inflammation, which is known as encephalitis. Up to 30 percent of patients who develop encephalitis caused by Japanese encephalitis virus will die. Among those who survive, the outcomes aren't very good. Many suffer from severe neurological sequelae or cognitive deficits, and this disease, in places where it's endemic, causes a substantial public health burden. It can cause devastating outbreaks, and even during times when it's not causing an outbreak, it's always an important contributor to mortality and morbidity in places where it's endemic. The best way to prevent Japanese encephalitis virus is through human vaccination. So, we have good vaccines that protect people, and if you are vaccinated, you should be protected from a mosquito bite. These public health intervention tools are being used in many parts of the world where Japanese encephalitis virus is a risk, although unfortunately, not in all places. This map shows you the global distribution of Japanese encephalitis virus infection. You'll see in red the areas of Japanese encephalitis risk, and this covers much of south and Southeast Asia up north through China, and of course Japan, where the virus was first discovered and where it got its name. You can also see that risk areas include part of the very north of Australia, and this is a relatively new development, and indeed, with climate change, we suspect that the vectors that are competent for transmitting Japanese encephalitis virus may have even more habitat where they can live very happily, so the areas at risk for Japanese encephalitis may grow. Today, we're going to talk specifically about Bangladesh. You can see Bangladesh circled here in yellow. It's clearly within the Japanese encephalitis risk area. In the 1970s, there was an outbreak of Japanese encephalitis described in Bangladesh. But other than that, there had never been any routine testing or surveillance for Japanese encephalitis there until 2003. So, 2003-2005 was the beginning of a surveillance network for Japanese encephalitis in Bangladesh. In those initial two years, there were four hospitals, you can see those marked in red here on the Bangladesh map, four hospitals participating in surveillance. The initial findings showed that up to 10 percent of patients who presented to these hospitals with encephalitis had Japanese encephalitis virus infection. This was a major finding, and in fact, it was the commonest cause of encephalitis among the patients that were included in surveillance. So, as soon as we started this first surveillance program, we saw that this was an important contributor to the burden of disease in Bangladesh, and we wondered what can we do to further investigate, to estimate the burden of mortality, to decide whether or not vaccine might also be useful in Bangladesh, was being used in many other countries, and we wondered if it would be worthwhile for Bangladesh as well. So, following this first two years of surveillance, we decided to continue this surveillance. Although, the hospitals included in that second round of surveillance changed a bit. They're shown here. So, two of the sites remain the same but two changed, and we continue to collect clinical data from patients who are presenting with encephalitis as well as biological specimens, and those were sent to the capital in Dhaka for laboratory testing to confirm human cases with Japanese encephalitis. Now, what are the data reporting within this system look like? So, basically, there were these four hospitals, and they reported to the icddr,b, which is a health and population research institute located in Dhaka, Bangladesh. They were funded and responsible for the day-to-day organization and implementation of the Japanese encephalitis surveillance program, and I had the honor of being a part of that team. Once we collected the clinical data and linked that up with the laboratory results, some of which was confirmed at laboratories in the CDC, we then pass those surveillance data onto the Institute for Epidemiology, Disease Control and Research, with the Ministry of Health and Family Welfare of the Government of Bangladesh. They then made the data publicly available. I want to give you next, just an idea of some of the important data to come out of this surveillance program. So, what this figure shows you along the x-axis are the years of surveillance. So, you can see the first bar represents data from 2003-2005, the second from 2007 when the surveillance started again, all the way through 2013. At the end, you'll see a bar that represents the total number of patients here in the figure, which is 314. Along the y-axis, you see proportions. In fact, the proportion of JE cases identified in any given year by age group. So, along the top, you see the legend for the different colors. There's a dark gray, a medium gray, and a lighter gray. The dark gray are children, zero to five years old. The lightest shade are children age 6-15. Then the middle gray color is at the top, and that represents people aged at least 15 years, and primarily represents adults. So, if we look at this figure showing the distribution of ages of JE patients in Bangladesh, we see that on average, about 50 percent or more are adults. Now, this finding was really important, because most countries that had introduced Japanese encephalitis vaccine, did so as part of the routine immunization program for children, and so, what our data showed was that even if Bangladesh did implement vaccine into its childhood immunization program, the majority of people at risk who are adults would not be protected. So, what that meant is that Bangladesh either should choose to vaccinate all people in the populations at risk, or if they started with children, had to understand that it would take many decades before the public health burden from Japanese encephalitis was reduced substantially. So, over these many years of surveillance, we collected important data. Now, next, let's think who are the stakeholders for these data and for this public health surveillance system? I want you to take five minutes to consider who the stakeholders for this JE surveillance in Bangladesh might be. Write down all the possible stakeholders you can think of. Think about who would be interested in these data, but even more importantly, who will need to act on these data for the benefit of public health? Because those are very important to include in your list of stakeholders. When you're done with your list, come back to the lecture and we will discuss further.
