Category: Infectious Diseases
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…)
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…)
Mosquito-borne illnesses may increase due to global warming
Mosquito bites are such a nuisance. They itch intensely for days, you can't help but scratch them, and you are left with a scar to remember them by. For much of the world, this is the aftermath of a mosquito bite. But in warm tropical climates, mosquitos are carriers of a variety of microbes pathogenic to humans. Dengue, malaria, West Nile, yellow fever, and Zika are all examples mosquito-borne illnesses. (more…)
Tricking the Immune System: Antigenic Variation and Host Molecular Mimicry
Halloween has finally arrived and everyone around you has been busy working on their costumes in anticipation for this glorious day of tricks and treats. Come Halloween night, you may not even recognize the faces behind the costumes. How would you tell apart friends with a sweet tooth from foes ready for some tricks?
For some bacteria, putting on costumes is an everyday event when it comes to tricking the immune system. The immune system distinguishes the body's own cells from those of invading bacteria and viruses. Since the microbe's outer membrane is usually the first thing the immune system sees, the body takes advantage of molecules found on the outer membrane to generate an immune response. This seems like a wise defense mechanism but microbes have several tricks up their sleeves; they disguise themselves from the immune response by changing molecules on their outer membrane (antigenic variation) or by turning on and off expression of genes encoding for surface molecules (phase variation). (more…)