An Early Warning System to Help Fight Cholera
June 14, 2011
A scanning electron micrograph of Vibrio cholerae, the bacteria that causes cholera.
Across the developing world, cholera—which hasn’t seriously threatened the U.S. for a century—is a major problem. That’s not likely to change soon. In fact, it is likely to become an even greater scourge. People are still going to suffer.
But today, a new early warning system is promising to reduce suffering and deaths from the disease by predicting outbreaks before they start.
Scientists from the International Vaccine Initiative in Seoul, Korea are developing the framework for a cholera warning system based on data from cholera-endemic areas of Tanzania. The IVI scientists found that a one-degree Celsius increase in temperature above the average monthly minimum signaled that cholera would double in the region within four months. Similarly, a 200-millimeter increase in monthly rainfall totals provokes a spike in cholera cases within two months.
The model sorts these key factors out of the noise: IVI found that other factors, like humidity and sea-surface temperature fluctuations were not as closely associated with cholera outbreaks.
Cholera bacteria thrive in warm water where sanitation is poor, spreading mainly through fecal contamination of food and water. So it makes sense that hotter, wetter conditions should prompt communities to start preparing for an outbreak, the scientists noted in a paper recently published in the American Journal of Tropical Medicine and Hygiene. (The journal is published by the American Society of Tropical Medicine and Hygiene, a Burness client.)
The findings represent a definite advance over common practice. Today, public health officials look only for clinical signs of a cholera outbreak: people getting sick. At that point, it’s too late for the cholera vaccine to have maximum effectiveness. By then, a large portion of the population is likely already carrying the bacteria, even if they aren’t exhibiting symptoms.
With an advance warning from IVI’s system, though, authorities could quickly launch a public health campaign – including an emergency vaccination effort to helping stem the spread of the disease before it spreads through the population.
This model comes at a critical time. In 2009, cholera sickened more than 220,000 people around the world, and killed 5,000, according to the World Health Organization. Outbreaks of the disease, common in sub-Saharan Africa and parts of southeast Asia, are increasing in frequency and severity – in large part due to climate change. And the Intergovernmental Panel on Climate Change reports that average global temperatures could rise more than four degrees Celsius by the end of the century.
The result of these changes? If every one-degree Celsius increase doubles cases of cholera now, the situation might get eight times worse. This will pose a massive public health challenge. But with an early warning system, officials, caregivers and citizens will have a chance to prepare, and the knowledge to act.
