Posts Tagged ‘cholera’

Cholera: Part two, the nearby 21st century epidemic

Tuesday, February 26th, 2013

Until 2010 I hadn't thought much about cholera in the modern era. I had considered it a disease from the past  and associated it with Dr. John Snow, the father of modern

Algae can carry cholera bugs a long ways

epidemiology , the study of the patterns, causes and effects of health and disease in defined populations (Hippocrates, the famous Greek physician is considered the ancient father of the field).

I was clearly wrong in doing so.

I had previously read parts of the science writer Laurie Garrett's first two books, The Coming Plague: Newly Emerging Diseases in a World Out of Balance published in 1994 and Betrayal of Trust: the Collapse of Global Public Health which followed in 2000. Her first book touches on cholera in Africa and then has a section on the seventh Global Pandemic starting in 1961 in Indonesia's Celebes Islands.

Now I read Chapter 16 of The Coming Plague in detail. It mentioned that Rita Colwell, PhD, an  environmental microbiologist, was convinced in the 1970s and 1980s that bacteria and viruses could be carried in algae, the world's  oldest living life form. Algae are responsible for "red tides"  (AKA Harmful Algal Blooms or HABs), episodes when those ocean plants massively increase in number then produce toxins making shellfish dangerous to eat and killing off fish.

Colwell found that the bacterium responsible for cholera could survive encysted in algae and float long distances in their "plant capsules." The El Tor strain of the bug was responsible for the 1991 epidemic in Peru. The CDC's publication Morbidity and Mortality Weekly Report, AKA MMWR, mentioned that outbreak in its February 15, 1991 editionMMWR noted this was the first appearance of cholera in South America in the 20th century and recommended exclusive use of boiled water for drinking, careful cleaning of fruits and vegetables, and avoidance of raw or inadequately cooked fish or other seafood. It stated the risk to U.S. travelers was low.

In the next eleven months cholera claimed over 330,000 victims in the Western Hemisphere, killing just over 1%. Lima, the Peruvian capital, had stopped chlorinating its water and Peruvians often ate ceviche, uncooked fish and shellfish mixed with lime juice. By the Fall of 1993, 8,000 deaths and over 900,000 cases of cholera were reported in Latin America. The El Tor strain of the cholera bacterium had become endemic in the region.

A 1994 article in the Journal of Clinical Microbiology documented the next chapter in the modern history of cholera. A new strain struck in December of 1992, first in the Indian city of Madras and then spreading to Calcutta, Bangladesh and Thailand. Even those who had previously been through a siege of cholera were not immune to the O139 strain as the Bengal cholera Vibrio was termed.

An earthquake can be both a disaster in itself and the seed for an epidemic.

The Western Hemisphere would have another cholera epidemic eight years later. In the January 10, 2010 a major earthquake in Haiti occurred. Although its magnitude on the logarithmic Richter scale was "just" 7.0, while the offshore earthquake in Japan in 2011 was an 8.9 (an 8.0 quake is 10 times as intense as a 7.0 and a 9.0 is 100 times as powerful), the depth of the Haiti quake was ~half that of the 2011 tremor in Japan and it struck a major Haitian city. The damage was immense and the local infrastructure was severely disrupted with healthcare, water and sanitation being affected.

A recent New England Journal of Medicine article (Feb 14, 2013) reviewed the surveillance efforts during the subsequent two years. Prior to the earthquake, less than two thirds of Haiti's population of 9.8 million had access to even the lowest category of an improved water source; less than an eighth drank treated water from a pipe system and only a sixth lived with adequate sanitation. The 1991 Peruvian cholera didn't reach Haiti so there was little or no prior immunity to the El Tor Vibrio strain.

The results were predictable, a major outbreak of cholera, but the government and international medical assistance markedly ameliorated the epidemic. Through October 20, 2012 over 600,000 cases of cholera were reported and 7,436 deaths resulted. The case fatality rate was initially high in some locales (4.6%), but within three months of the start of the epidemic it fall to the World Health Organizations target of <1.0%.

In comparison there were 2.8 million cases of cholera globally in 2011 with 91,000 deaths (3.25%). The CDC notes that twenty-three cases occurred in the U.S.; 22 were associated with travel to Haiti, one with consumption of food products from that country.

The treatment of cholera is relatively simple: the WHO says rehydration with oral rehydration salts is enough in almost all cases. Intravenous administration of fluids can be life-saving in especially serious cases.

But how about preventing the disease?  A Perspective column in the same journal edition (NEJM Feb 13, 2013) is titled "The Cure for Cholera--Improving Access to Safe Water and Sanitation." The three authors, all with dual MD, MPH degrees, note that the malady is still a major source of illness and mortality in the developing world with WHO estimating 3 to 5 million cases and 100,000 to 200,000 deaths a year.

In the treatment arena, they note that antibiotics should be given to those with even moderate dehydration, that all patients should receive zinc, which can decrease the duration of diarrhea, and a newer variant of the two-dose vaccine should get wider usage.

Safe drinking water and modern sewage disposal is still a major issue for many in 2013: two and a half billion live without adequate toilet facilities and nearly 40% in the least developed regions of the world don't have bacteria-free water to drink.

More than a billion of the poor and marginalized need help. But estimates of $50 billion needed per year are daunting in these tough economic times.



Cholera: Part 1 background and history

Sunday, February 24th, 2013

An 1882 monument to victims of cholera

Cholera is an infectious illness, found only in humans, caused by a bacteria in contaminated water, leading to severe diarrhea and dehydration and capable of killing its victims in a matter of hours if untreated. When I read about the disease for the second time in decades (the first time was after a 21st-century epidemic in Haiti), I was amazed at how quickly a victim can lose 10% or more of their body weight in severe cases; e.g., eight quarts between my normal bedtime and when I usually wake up. Many people who ingest the bacteria don't develop any symptoms, but if they do and lack modern re-hydration therapy, their chance of dying is 40-60%.

In all likelihood it is an ancient disease with writings from the lifespan of Buddha  (563-583 BCE) and from the time of Hippocrates (460-377 BCE) revealing diseases that presumably were  cholera. It has, over the last several hundred years, been a major killer of mankind, causing millions of deaths in the 19th century.   Those numbers place it among the deadliest of infectious illnesses, in the company of smallpox, the Spanish flu, bubonic plague, AIDS and malaria.

A CBC News article online with the title "Cholera's Seven Pandemics," starts with a major outbreak in India near the Ganges River delta. Between 1817 and 1823 there were 10,000 deaths among the British soldiers stationed in that country, estimates of hundreds of thousands of fatal cases among native Indians and 100,000 dying in Java in the year 1820. The second pandemic began in 1829, again in India, and spread to Russia, Finland, Poland, England, Ireland, Canada, the U.S. and Latin America, before another outbreak in England and Wales that killed 52,000 over two years. The sixth pandemic killed more than 800,000 people in India alone and, over the next 24 years swept over parts of Europe, Russia, northern Africa and the Middle East.

The National Library of Medicine's website entry on cholera associates it with crowding, poor sanitation, famine and war. India has remained a source as the disease is endemic (ever present) there. People get cholera by eating or drinking either contaminated food or water; the medical term is the fecal-oral route.

In the summer of 1854 London was the epicenter of a deadly outbreak. Dr. John Snow, a famous British physician born March 15th, 1813, had been noted as a pioneer in anesthesiology, using chloroform to assist in Queen Victoria's delivery of her eighth child in 1853.

Then, as documented in the book, The Ghost Map by Steven Johnson, Snow turned his investigative talents and keen mind to cholera, becoming in the process the modern father of epidemiology.

London's population had grown immensely and its sewage system was antiquated. In addition to basements filled with excrement, cesspools and drainage into water sources were rampant. A major concept of disease causation was the miasma theory. The term means "bad air" and the assumption was illness was caused by the presence in the air of a miasma, a ill-smelling vapour containing suspended particles of decaying matter .

Snow, on the other hand, felt cholera was caused by something ingested, most likely by drinking water contaminated by waste products.

In a painstaking and extremely clever investigation, Snow had, in a prior cholera outbreak in 1849 which was responsible for a dozen deaths in flats in a slum area, shown that two separate  sets of milieu had markedly differing death rates. All environmental parameters were essentially identical in the two groups with one exception; where they obtained their water. The group who suffered a much higher rate of illness got theirs from a company whose river source was in the same area where many sewers emptied.

Vibrio cholerae, the cholera bacteria

Five years later a much larger cholera epidemic provided an opportunity to more closely examine the water sources of the victims. One particular pump, seemingly providing clear water, proved to be the culprit. The Broad Street pump's output was examined by a Snow's colleague, a skilled microscopist Dr. Arthur Hassall, and found to contain what Hassall believed to be decomposed organic matter with oval-shaped tiny life-forms felt to be feeding on that organic substance. Snow was not aware then of the 1854 work of an Italian scientist, Filippo Pacini, who had examined the intestines of patients dying from cholera in Florence and found a comma-shaped bacillus he termed a Vibrio.

The proponents of the miasma theory did not yield easily, but Snow's map of the location of deaths from cholera eventually let his hypothesis of a water-borne illness prevail.  Then an assistant curate (church figure in charge of a parish) named Henry Whitehead who had read Snow's papers on the epidemic eventually found the index (first) case, a baby Lewis. As a result, the Broad Street pump was excavated and a direct connection to a cesspool was found.

The juxtaposition of Snow's scientific data and Whitehead's work as a beloved neighborhood figure led to the local Vestry Committee's report endorsing the water-as-culprit theory.

The city subsequently launched a major project to carry waste and surface water away from Central London.





Five years later, he