Tag: pathogens
A Public Health Detective Story: John Snow, Cholera, and the Germ Theory of Disease
It’s 1854 in London. The third major cholera pandemic was racing through the city. Spreading from the Ganges delta of India since 1837, it’s claimed over a million lives mostly among Asia, Europe, and North America.
Within the Soho district of Westminster, London, things weren’t looking good. The London sewer system had not reached Soho, but a large influx of people had. Animal droppings from cowsheds and slaughter houses lined the streets. Many cellars had cesspools underneath, formed from the sewage and filth seeping in from outside. Making matters worse, the London government was dumping waste into the River Thames and contaminating the water supply. (more…)
Secret Serratia: Then and Now
If you’re a microbiologist, the acronym HGT may have you thinking about horizontal gene transfer, the transfer of genes between microbes. But during the months of November and December, HGT takes on a different meaning: holiday gift transfer. As part of the annual #SecretSerratia holiday gift exchange, pairs of microbiologists exchange gifts, usually science and microbiology related.
I eagerly signed up to participate and my Secret Serratia and I swapped gifts and shared photos of our microbial gifts on Twitter, along with ~70 other microbiologists. (more…)
Move over flu season, there’s an entire epidemic calendar
Flu season is upon us, but there are actually “seasons” for many other infectious diseases. Chickenpox outbreaks peak each spring and polio transmission historically occurred in the summer. In fact, at least 69 infectious diseases vary seasonally.
Micaela Elvira Martinez, assistant professor in the Department of Environmental Health Sciences at Columbia University, found this out by systematically querying the data of 69 infectious diseases for seasonality. She chose the diseases to study based on those that were of public health interest (including neglected tropical diseases). She searched the literature for a disease name + season and/or disease name + season + human and collected information from the publications found. When needed, she searched for disease name + “seasonality.”
What she found was that seasons matter – but it’s more complicated than cold weather keeping everyone cooped up indoors. Martinez categorizes the impact of seasonality into four factors: environmental, host behavior, life cycle events, and exogenous biotic factors. What’s more, all of these factors can influence disease epidemiology at many levels: from hosts, to reservoirs, and to vectors. (more…)
Acute Oak Decline: A Modern Adaptation of Koch’s Postulates
In the UK, thousands of oak trees are “bleeding,” oozing dark liquid from cracks on their bark. What lies underneath are fluid-filled necrotic cavities that disrupts their life force by impeding the normal flow of nutrients and water. Taking advantage of the weakened state of the trees, are bark-boring beetles, which lay their eggs in the cracks of the bark. These are the characteristic signs of Acute Oak Decline, a disease that can kill a tree within four or five years of symptom onset.
Acute Oak Decline made its appearance in 2008. Now, scientists have found that Acute Oak Decline is caused by a polymicrobial infection – in this case, a simultaneous infection of three bacterial species: Brenneria goodwinii, Gibbsiella quercinecans, and Rahnella victoriana. With the microbes (B. goodwinii and G. quercinecans) and beetle larvae in hand, the researchers were able to replicate the characteristic signs of Acute Oak Decline. (more…)