Posted on 21st July 2008 by Judy Breck in biology | ecology | health
biodiversity, birds, dilution, transmission, virus, west_nile
The illustration for this learn node is from a Tufts University on “Emerging Infections and Agents of Biological Warfare.” The West Nile Virus transmission cycle is also illustrated in a chart at the Centers for Disease Control and Prevention (CDC). An interesting angle on the transmission is that protecting biodiversity of birds slows it down, as described in a Public Library of Science article:
We found there is lower incidence of human WNV in eastern US counties that have greater avian (viral host) diversity. This pattern exists when examining diversity-disease relationships both before WNV reached the US (in 1998) and once the epidemic was underway (in 2002). The robust disease-diversity relationships confirm that the dilution effect can be observed in another emerging infectious disease and illustrate an important ecosystem service provided by biodiversity, further supporting the growing view that protecting biodiversity should be considered in public health and safety plans.
Posted on 3rd September 2007 by Judy Breck in biology | health | molecules, cells
cells, polio, poliomyelitis, virus
Polio invasion is seen in this learn node illustration. The little purple ball – lower center in this image – is a very scary thing. It is polio entering a person’s gut. Good public health can prevent polio and many other human miseries. Superb learning materials for public health practitioners are available as open education resources OER at Johns Hopkins Bloomberg School of Public Health. The image above combines slides 26-28 from an OPENCOURSEWARE course on Public Health Biology. The exact location for these OER lectures, which are open for you to download, is: Module 2: Pathogens and Host Immunity > Lecture 3: Pathogens: Nature and Transmission. This is the text that accompanies the illustrations above:
Poliovirus Viron (left image):
30 nM diameter virion contains 60 copies each of four proteins (encoded in the viral RNA) – Viral RNA is a single strand mRNA (+) polarityi, is about 8000 bases long, and encodes 11 proteins – Viron is non-enveloped and contains no enzymes
Poliovirus: Intracellular Replication (right image):
1. Attachment to cell via specific receptor (Vpr) on cell membrane 2. Virus entry (endocytosis); extrusion of RNA into cytoplasm 3-5. Translation of viral RNA; processing of polyprotein; formation of RNA replicase protein 8-10. Replication of viral RNA 11. Continued translation and processing; formation of virion proteins 12. Assembly of (+) RNA and rivon proteins into new virions 13. Virion release into the gut
MORE POLIOVIRUS LEARN NODES:
For more about the ongoing fight against polio, the Stony Brook University School of Medicine published an open access article in Virology Journal: “Epidemics to eradication: the modern history of poliomyelitis.”
For a look at sleuths who are tracking the polio viruses as they invade our cells try this open access article from the Public Library of Science BIOLOGY: “Imaging Poliovirus Entry in Live Cells.”
More learn nodes at: learnodes.com
