A Q&A with Dr David Sack on the History of Oral Cholera Vaccine (Part 2 of 3)
Cholera persists as an important public health problem in more than one-third of the world’s countries and is endemic in approximately 69 countries. A cholera outbreak can be extremely dangerous and can cause outbreaks affecting thousands within just a few days from the first case of infection. However, the global burden of cholera is not precisely known. The lack of accurate reporting is due to limited capacity for disease surveillance in cholera-affected countries, as well as social, political, and economic disincentives for reporting cholera. Listen to the audio or read the transcripts below to hear Dr. Sack expand on cholera hotspots and issues regarding cholera surveillance.
Dr. Sack recently appeared as a guest lecturer for the online course, Current Issues in Public Health, at the Johns Hopkins Bloomberg School of Public Health. As part of the course, students had the opportunity to submit questions for Dr. Sack online.The audio and transcripts below capture the conversation between Dr. David Sack, Dr. Edyth Schoenrich, and the Teaching Assistant as Dr. Sack answers students’ questions.
Q: Are there places where cholera is more endemic? Are there certain countries or regions where it’s known to always be or does it move around?
David Sack: There are certain areas where it is high risk. Just to point out - when you’re drawing maps of the world to show where a disease occurs, you paint the picture and for example, if cholera is occurring in the Democratic Republic of Congo, you paint all of Congo in one color. So, that doesn’t show you really where in Congo the problem is. In fact, most of the Democratic Republic of Congo is free of cholera. So I think many countries have these hotspots within the country, so you need to know much more about where the high risk area is.
Q: That actually leads to the questions we had about surveillance, which can be very difficult for different types of diseases. How can we improve surveillance? Do you have any experience with systems of village-elected trackers?
DS: It’s certainly something that we talk about; the official WHO case definition is if a person over the age of five develops severe, acute watery diarrhea leading to death or shock, then this would be suspected of being cholera. Of course to be confirmed cholera, you should have a culture to confirm that. These cases can occur in parts of the world where there’s no laboratory, there’s no physician to make that diagnosis and the idea of using community health workers and a lot of people are very interested in the use of cell phones and SMS messaging. This is the new frontier – how do you do this? The other part of that is a confirmation that is do you need a culture? After looking at data from South Sudan, when a specimen was taken at the hospital and sent for a culture, the average time for a report to be returned was two weeks. That’s not a very practical situation. So, one of the activities we’ve been working on is the use of a dipstick test, which seems to be working very well.
Q: How available is that (the dipstick test) in the greater global sense?
DS: Well, it’s commercially available. It costs about $2 per test. It’s not something you could have everywhere, but certainly something you might have in the regions or districts.
Q: Is that test something that’s necessary before you treat? How distinguishable is cholera; does it look like other diseases?
DS: You do not need a confirmed diagnosis to treat. If you have a patient with severe dehydrating diarrhea, you treat the patient for dehydration. Most facilities in the developing world know the standard methods (Plan A,B,C). You do not need to know the diagnosis; you treat according to the symptoms.
Q: What would trigger a quarantine or thinking that this is something more than what is usually seen?
DS: We don’t quarantine anymore, but if you have a cholera outbreak, that should stimulate a public health response. That facility, that district needs to be aware that they have to quickly set up the facilities for cholera treatment. If you treat people properly, nobody should die, but if you don’t have the treatment facilities available, the case fatality rate could be 50%. An outbreak could spread very quickly and if you can intervene quickly, you may be able to stop the spread, stop the transmission.
Q: What are the requirements for the protection of the health workers who deal with the patients in treating their dehydration?
DS: Interesting question, because frequently we see hospitals going overboard in their protection of health workers. That is, walking through chlorine to get into the cholera treatment center. Even putting the cholera ward at a distance from the main hospital. In general, these are not necessary. You do need proper hand washing, proper care. I worked on a cholera ward for 15 years and we used to treat about 50,000 patients a year with cholera and there was never a nurse or a doctor who ever got cholera.
Dr. David Sack, M.D, is a professor of International Health at the Johns Hopkins Bloomberg School of Public Health. He has spent his career devoted to the control of infectious diarrheal diseases like cholera, rotavirus, and diarrhea due to enterotoxigenic E. coli. In addition to directing the Delivering Oral Vaccine Effectively (DOVE) project, he is also head of the Enteric Laboratory at the Johns Hopkins University Center for Immunization Research, which carries out clinical trials of new enteric vaccines.