June 13 - Marburg virus

In 1967, in the German town of Marburg, 31 people became very ill with a strange new disease - 7 of them died. Many of the people who had become ill were involved with research on polio vaccines and were exposed to monkeys that had been originally imported from Uganda. The culprit was a virus, and it came to be known as Marburg virus, after the town. Marburg was the first filovirus to be discovered and is closely related to Ebola virus. It is transmitted from primate to person or person to person via exposure to infected body fluids such as blood or saliva and can produce rather horrific symptoms, including jaundice, delirium, and liver failure, as well as hemorrhaging. Untreated, it can have a fatality rate of as high as 90%. In 2008, the first case in the U.S. was reported, though the patient acquired the virus in Uganda. Vaccines are currently being developed.

March 11 – Sputnik virus

As noted by the Jonathan Swift quote at the top of this blog, many parasite themselves are infected with parasites. These obligate parasites of other parasites are called "hyperparasites". Parasitoid wasps that infect and enslave caterpillars can themselves be impregnated by hyperparasitoid wasps, parasitic crustaceans like Sacculina are parasitized by bizarre hyperparasitic isopods, some parasitic flukes are infected by protozoan and bacterial parasites. Viruses cannot replicate on their own and must inject their genetic material into the cell of their host, hijacking its cellular machinery for its own replication, thus making them obligate intracellular parasites. In 2008, it was found that some viruses themselves can become infected by other viruses. In this case, the host is the virus you met yesterday, a strain of mimivirus, and the parasite belongs to a previously unknown group of virus that have been termed "virophages". Bernard La Scola and colleagues discovered that these hyperparasitic viruses, which they named "Sputnik". Each of these Sputnik measuring 50 nm in size, and just as more traditional virus hijack the machinery of their host cells for replication, the Sputnik commandeers the "viral factories" of the mimivirus to churn out more virophages at the host's expense. In a case of "you are what you eat" (in this case "you are what you infect"), the virophage's own genome is littered with genes from its own host, some of which are genes that the mimivirus itself had also acquired from the cells it infects, making the virophage a strange genetic chimaera.

Contributed by Tommy Leung.
Image from this source.

March 10 – Mimivirus

Mimivirus is part of the Mimiviridae, a group of "giant viruses", which compared with viruses most people are for familiar, with such as influenza virus, HIV, or Ebola virus, are unusual in many ways. In fact, mimiviruses are so different that they challenge the traditional concept of a virus and even the definition of life itself. Measuring 400 - 800 nm in diameter, mimiviruses are the giants of the virus world. Their viral particles themselves are unusually large and complex and this complexity is also reflected in their genome which is huge for a virus. Their genomes contain 1.18 million basepairs, which is more than 600 times larger than the genomes of any of the viruses named above, but also even larger than many bacteria (e.g. Treponema and Chlamydia). And unlike "normal" viruses, which only have a few genes (e.g. 9 genes in influenza), mimivirus has more than 900 genes and many are genes that otherwise have only been seen in cellular organisms. The strain of mimivirus in this context infects Acanthamoeba spp, which are free-living, bacteria-eating amoeba, commonly found in soil and freshwater habitats.

Contributed by Tommy Leung.
Image from this site.