In this blog post, we will look at how cholera, which once terrorized humanity, has become a disease that can be prevented and treated with the development of modern medicine.
In the Korean novel “Toji” by Park Kyongni, there is a scene in which a scholar dies painfully from being infected with the plague. A healthy person suddenly goes crazy and visits the bathroom, only to die a few days later. Shortly after that, the villagers also died one after another in a similar manner. This catastrophe was cholera, a disease that terrified not only Joseon at the time but the entire world. Cholera took the lives of many people from the 19th to the early 20th century and continues to pose a deadly threat in the developing world.
Infection with cholera is accompanied by severe diarrhea and vomiting, which causes a rapid loss of water and mineral salts. If this condition is not treated, death occurs within a short period of time. The toxin secreted by Vibrio cholerae acts on the epithelial cells of the small intestine to cause these symptoms, and a systematic understanding of the mechanism of action of the toxin is necessary for the effective treatment of cholera. This toxin disrupts the G protein signaling system in the body, and as a result, the small intestine epithelial cells lose their normal ion concentration regulation function. This causes the water and salt balance inside and outside the cells to be disrupted, resulting in rapid dehydration.
The common route of infection for cholera is through contaminated food or water. When you eat spoiled food or drink contaminated water in the summer, a large amount of cholera bacteria reach the small intestine through the digestive system. Cholera bacteria that attach to the small intestine wall, especially to epithelial cells, synthesize a toxin protein called CT, CTX, or enterotoxin, which adversely affects the body. This toxin is a complex composed of six protein subunits, five of which are responsible for firmly binding the toxin to the epithelial cells. Once the binding occurs, the remaining one subunit enters the epithelial cell and disturbs the G protein signaling system.
The mechanism of action of cholera toxin is an important topic of biochemical research today. In particular, understanding the process by which cholera toxin prevents the inactivation of G proteins is essential for developing effective treatment and prevention strategies for this disease. G proteins play a key role in intracellular signaling, amplifying the necessary biological responses in the cell in response to external stimuli and, as a result, performing specific functions. However, cholera toxin blocks the process by which G proteins are naturally inactivated, preventing cells from functioning normally. In particular, in the case of small intestinal epithelial cells, this causes chloride ions to continue to leak out of the cells, while sodium ions cannot enter, resulting in a severe imbalance in ion concentration. As a result, water also continues to leak out of the cells, causing rapid dehydration.
Rapid loss of water due to dehydration is the main cause of death in cholera patients. Therefore, the main treatment for cholera is fluid therapy, and antibiotics are also used, but this is mainly only chosen in urgent situations. In fact, even without the use of antibiotics, our body’s immune system can produce antibodies to eliminate cholera bacteria. Thanks to these advances in treatment, the mortality rate from cholera has been significantly reduced compared to the past.
However, the best way to deal with diseases like cholera is prevention. Cholera is a disease that causes severe suffering, so it is important to prevent it in advance. The basic way to prevent cholera is to wash your hands frequently and to cook food thoroughly. This is very effective because cholera bacteria are killed by heating at 55°C for 10 minutes. In addition, a vaccine has been developed, but it has not yet been very effective. This is likely to be related to the short incubation period of cholera bacteria, which is 1-2 days, but the exact reason has not been identified and further research is needed.
If more in-depth research is conducted on the exact mechanism of cholera, there is a high possibility that a more effective vaccine will be developed. If such a vaccine is widely distributed in the third world, cholera will become a manageable disease rather than a major threat to humanity. Historically, cholera has been a disease that has left deep scars on human society, but with the development of modern medicine, its deadly impact is gradually decreasing. In the past, it was so threatening that it could devastate a community, but now it is recognized as a disease that can be systematically prevented and treated. If research and countermeasures against infectious diseases such as cholera continue to advance, we will be able to completely escape from such threats someday.
