There is a nice list of global health wins this year from Karl Hofmann, President and CEO of PSI, the world’s largest social marketing firm. You can see his list on the Huffington Post. Highlights include exciting progress on a malaria vaccine, “Treatment as Prevention” for HIV, and progress on the rate of vaccination against pneumonia.
December 30, 2011
December 28, 2011
NPR Highlights Two Global Health Technologies
There were two interesting global health technology stories on NPR’s All Things Considered today. The first story focuses on the Liter of Light project in the Philippines, in which a one-liter bottle of purified water diffracts sunlight and provides as much light as a 55-watt electric bulb. The second story is the second in NPR’s series of young innovators, which highlights the work of Marian Bechtel, who is working to detect landmines using sound. Listen to the story here.
September 10, 2010
Cholera pandemic continues
Did you know we are in the middle of the Seventh Cholera Pandemic? And that we have been since 1961? From 2007-2009, many countries were affected by cholera (Figure 1), which is still estimated to cause as many as 130,000 deaths a year. Cholera remains one of the most horrible ways to die, which can happen in as few as 24 hours if left untreated. And it can live especially well in brackish, warmish water, which we may well have more of if global climate change continues (see my other posts on this topic). So, what can be done?
Figure 1. Cholera outbreaks world-wide from 2007-2009. Taken from World Health Organization
There are cholera vaccines, and they are safe and effective. Two of the more routinely used are Dukoral and Shanchol/mORCVAX. Clinical trials of both have been conducted in endemic cholera regions, and have demonstrated good results. One of the possible drawbacks to their use is cost-effectiveness. Studies have shown that using simple models, even $0.50 per dose is not cost-effective. However, when herd immunity is considered, then cholera vaccines do become cost-effective. A model-based calculation of the critical immunization threshold is around 50% for Bangladesh, although local epidemiology might change this for other regions.
All this information about cholera, and yet it continues to kill hundreds of thousands of people a year. Why is this? Part of the reason is the speed – by the time information about an outbreak can travel to the people who can help, it is often too late for many. Second, vaccinations are not routine, and even the WHO suggests they not be. Rather, the solution to cholera is as simple as it has ever been: do not eat poo. This is harder than it sounds. One needs safe drinking water, good sanitation, and effective microbiological surveillance. A recent outbreak of E. coli in the drinking water of White Rock, BC had people boiling their drinking water for more than a week, and there’s currently E. coli contamination on Vancouver Island, which has resulted in a boil water advisory there. Cholera was a major problem at our latitude until 1923, and there’s no reason it can’t come back. Vigilance is the price we must continually pay for the health we enjoy here and around the world.
August 15, 2010
Old killers are new again: real-time epidemiology to the rescue
As with much in life, cycles of disease emergence and repression repeat themselves on the time scale of decades. Lately, many neglected and un-neglected diseases that we had under control have re-emerged as epidemic outbreaks again. Examples include dengue fever in the Caribbean and respiratory diseases in El Salvador, measles in southern Africa, and cholera in Pakistan. Part of the problem is that when a disease is under control, there are few cases and screening programs grow lax. Another part of the problem is that the underlying conditions for infectivity still exist. These include extreme population densities, poor sanitation, and difficult access to health care resources.
There have been designs for many years for remote monitoring stations capable of detecting disease before it becomes epidemic. These include water monitoring systems, remote biosafety and biosecurity systems that phone home if they detect something, and field-portable immunoassays for detecting disease on the spot. The major problem with most of these designs, however, is the connection between the presence of a pathogen and the likelihood of infection. Just because a pathogen is detected does not mean it will lead to an infection. Take for example the presence of fecal coliform in drinking water. Although this is a popular metric for water contamination, it does not always correlate with outbreaks of disease. In some cases, such a correlation exists, but these are usually the cases that are hardest to detect. Detection of 1-10 protozoans/mL in drinking water would certainly be helpful to indicate contamination, but at these concentrations, will anybody become sick?
These “grey areas” indicate the zones in which the minimum infectious dose (MID) is at or near the number of pathogens detected. As our analytical technology grows ever stronger, we can detect fewer and fewer pathogens, but is this useful? One often sees ridiculous detection limits cited in the literature for new analytical detection assays, but these are usually for contrived situations consisting of pure solutions or suspensions of the target of interest. A starting point, but what we really care about is relating this concentration to the risk of infection given certain criteria, like those listed above (dense population, etc.). This suggests a new line of inquiry into relating the detected concentration of a particular pathogen to the infection potential routinely in a given context. Luckily, such a real-time epidemiology is emerging. Los Alamos National Laboratory has a group working on such models, and better yet, Arizona State recently described a wearable monitor that could potentially interface with such models to provide local, real-time epidemiology data. Hopefully, in the next few years we will see a synthesis of these two data streams into a comprehensive whole, then begin the difficult task of distributing such technology to the populations at risk at a cost they can afford.
June 11, 2010
Recent advances in water purification
One of the major causes of death across the world is unsafe drinking water. Contamination with fecal coliforms (bacteria, viruses) as well as protozoans including Campylobacter and Giardia continues to be a major problem. To date, however, the methods used to detect at least some of these pathogens have been rudimentary at best. EPA Method 1623 is a protocol for testing “grab samples” of drinking water 50 L at a time and detecting protozoa through immunomagnetic capture and florescence observation. Some public safety labs then follow up with molecular methods, but at significant time and cost. Commercial Method 1623 kits cost upwards of $500 each, most of which comes in the antibodies used. This clearly is not a method that scales well.
As a result, many groups have dedicated themselves to developing technologies that are better. There have been three main approaches. The first seeks to kill everything living in the water through UV irradiation and/or chemical treatment, without regard to what the contaminants are. The second class of technologies seeks to filter out all contaminants independent of what they are. The final class of technologies seeks to identify and quantify the pathogens present, before countermeasures are taken.
The first approach, including emerging methods like advanced oxidation, is generally considered more direct and potentially quite effective. However, it can be power-intensive (~10 W-hr/L) and may not kill all pathogens present, particularly if such pathogens are recalcitrant. Certain UV methods can also suffer if the penetration of the UV is impeded through absorption by natural organic matter (NOM). The second method, filtration, also works well and can be quite cost effective. Examples here include sand filters and individual water purification filters presented by Michael Pritchard, although filters inherently become clogged over time and need replacing, giving rise to a potential supply chain problem. The third method may perhaps present an advantage in situations where routine monitoring is required, but where watersheds are protected and some sort of municipal water treatment is in effect.
This third method is still largely in the research phase, but recent progress has been encouraging. In particular, recently described methods including Dean flow microfluidics are now capable of separating particles by size at high flow rates (~L/hour) without any technology other than a simple pump. Recent work in dielectric impedance characterization also makes possible the analysis and differentiation of different cell types in a high-flow, low-power manner. It will be interesting to see if such systems can be scaled to municipal levels. A preliminary engineering analysis that I and coworkers conducted here at UBC seems to indicate that it can.
Flow rates and back pressures for Dean flow microfluidics. This analysis assumes 250 channels in parallel, each with a constant fluidic resistance sufficient to separate 5 micron from 10 micron particles.
