AsianScientist (Aug. 9, 2013) – Although malaria has afflicted us for more than 4,000 years, its actual cause was not discovered until the late 1800s. In medieval Europe, where the disease was widespread, it was thought for centuries to have been caused by toxic vapors from swampy marshland. In fact, the name of the disease is a reminder of this mistaken etiology: “malaria” is derived from the Italian “mala aria,” meaning “bad air.”
In 1880, Alphonse Laveran, a French military doctor working in Algeria, discovered the malaria parasite in blood samples from patients, but failed to find it in marshland air, water, or soil. He noticed, however, that the swamps teemed with mosquitoes, and suspected that the insects might harbor the disease. Soon after, Ronald Ross, a British army doctor based in India, found the parasite in the gut of a mosquito that had fed on a malaria patient, and went on to show that mosquitoes did indeed transmit the disease.
The discoveries of Laveran and Ross put to rest a medical myth that had persisted for centuries. But since germ theory, or the concept of disease being caused by infectious agents, was not put forward until the 19th century, it is not surprising that the toxic air theory made sense and took hold in medieval Europe. After all, health-related speculation, myths, half-truths, and urban legends abound even today, despite a plethora of scientific tools and expertise at our disposal to either debunk or lend credence to them.
Here’s a recent example, featuring uncannily similar actors. In June, haze from large swathes of Indonesian forest fires blanketed Southeast Asia in our own fog of “mala aria,” compounding public health woes in a region already experiencing its worst dengue fever epidemic in recent years.
As air pollution indices in Singapore and Malaysia skyrocketed to historic highs, the Internet buzzed with speculation about a silver lining to the dark cloud of haze: that it would kill off the dengue mosquito, or at least drive it into exile. And while dengue cases in Singapore spiked the week after the worst of the haze, they have been on the decline ever since – a trend that may serve to bolster this sentiment.
But is there any evidence to support this theory? A 2010 study carried out by Singaporean researchers analyzed eight years’ worth of environmental and epidemiological data, but found no association between dengue cases and air quality. In fact, the researchers noted that although Singapore experienced its worst haze in history from 1997 to 1998 (now eclipsed by the 2013 haze), dengue cases actually peaked during that period.
How then do we explain the current fall in dengue cases? Mosquitoes dying from air pollution is one hypothesis. But here are several more: The haze kept us cooped up indoors for a full week, and this reduced movement of people could have resulted in fewer opportunities for dengue transmission. Travelers may have avoided Singapore during the haze, resulting in a drop in the number of imported dengue cases, which can act as reservoirs to sustain transmission. Our herd immunity against the dengue viruses in current circulation may have improved (although how rapidly this can occur is unclear). Or, our mosquito control measures might finally be having a tangible effect.
It’s clear that no harm was meant by the online speculation. But, as the scenarios above illustrate, disease transmission is affected by the complex interplay of many factors, and pinpointing one of them without good evidence may have negative public health consequences.
The view that the haze has rid us of mosquitoes, if entrenched, may make us less vigilant about eliminating breeding sites in our homes and workplaces. In the eyes of the public, it may also belittle the mosquito control efforts of health departments, surveillance workers, and volunteers, possibly making it harder for them to do their job in the future. These issues are of concern because dengue cases have only been on the decline for several weeks, and time will tell if this is a sustained trend or merely a blip.
Perhaps the most dangerous misinformation in circulation today is propagated by the anti-vaccine movement, which claims that vaccines endanger children by causing severe conditions such as autism, sudden infant death syndrome, and brain damage. There is zero scientific evidence to support these claims; yet the scaremongering of this extremely vocal minority has made it very difficult for health authorities to convince spooked parents otherwise.
The consequences of this anti-vaccine rhetoric are already apparent. In Wales this year, health authorities struggled to stem an epidemic of measles by vaccinating some 40,000 schoolchildren who were born in the late 1990s but had not been not vaccinated as babies. This vaccine gap coincides with the 1998 release of an erroneous and now-debunked report that linked the MMR (measles, mumps and rubella) vaccine with autism and bowel disease.
Outbreaks of measles and other vaccine-preventable diseases such as whooping cough have also occurred in parts of the United States and Australia where vaccination rates have fallen to dangerously low levels. These extremely contagious illnesses can easily cross international boundaries, but at the same time are also highly preventable. The Wales outbreak has now been declared over after more than 1,200 measles cases and one death, but in fact should never have happened.
It is true that unconventional ideas can turn out to be correct, and that when they do, it can mean a huge advance for science. Laveran’s parasite and mosquito theories, for example, were initially met with widespread skepticism before he was proven right. Scientists and researchers are now better equipped than ever to put these theories to the test and to communicate the results to the public; however, keeping an open mind should not equate to letting speculation govern our way of life. In the words of Sherlock Holmes:
“It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts.”
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Copyright: Asian Scientist Magazine. Photo: acroamatic/Flickr/CC.
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