virology blog

About viruses and viral disease

measles

TWiV 48: Outbreaks near you

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twiv_aa_2001Hosts: Vincent Racaniello, Dick Despommier, Alan Dove, and Rich Condit

On episode 48 of the podcast “This Week in Virology”, Vincent, Dick, Alan and Rich revisit a vaccinia virus lab accident and viral vaccines produced in plants, then talk about an iPhone app to track infectious diseases, flying foxes, and an inhaled measles vaccine.

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Click the arrow above to play, or right-click to download TWiV #48 (58 MB .mp3, 79 minutes)

Subscribe to TWiV in iTunes, by the RSS feed, or by email

Links for this episode:
Laboratory acquired vaccinia infection
Medicago (investor presentation, pdf) and Fraunhofer produce vaccines in plants
iPhone app Outbreaks near me
No culling of flying foxes in Australia
Inhaled powdered measles virus vaccine
Herpesvirus latency confers symbiotic protection from bacterial infection (thanks Juliet!)
Porcine circovirus vaccine
Swine flu vaccine and Guillain-Barré (thanks Tom!)
The Great Flu and blog post (thanks Swiss compass and Allison!)
Building semiconductors with DNA (thanks Duncan!)
Email on viral classification (thanks Rodney and Eliot!)

Weekly Science Picks
Rich Stumbling on Happiness by Daniel Gilbert
Dick Eliot Porter at the Carter Museum and bookstore at Amazon
Alan Dr. Clarke’s H1N1 rap at the HHS sponsored YouTube contest
Vincent Coast to Coast Bio Podcast

Send your virology questions and comments (email or mp3 file) to twiv@microbe.tv or leave voicemail at Skype: twivpodcast. You can also send articles that you would like us to discuss to delicious and tagging them with to:twivpodcast.

TWiV 38: Measles

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twiv-200Hosts: Vincent Racaniello and Glenn Rall

On episode #38 of the podcast “This Week in Virology”, Vincent and Glenn Rall chat about koi herpesvirus, H1N1 influenza vaccine produced in insect cells, attack by a rabid raccoon, and measles.

[powerpress url=”http://traffic.libsyn.com/twiv/TWiV038.mp3″]

Click the arrow above to play, or right-click to download TWiV #38 (63 MB .mp3, 91 minutes)

Subscribe to TWiV in iTunes, by the RSS feed, or by email

Links for this episode:
Virus suspected in carp die-off: koi herpesvirus
H1N1 influenza vaccine produced in insect cells with baculovirus vectors
Outbreak of measles in Wales
Production of influenza vaccines in cell cultures: MDCK, Vero, PER.C6, EB66, insect (thanks Peter!)

Weekly Science Picks
Glenn Riddled with Life by Marlene Zuk
Vincent All the Virology on the WWW

Send your virology questions and comments (email or mp3 file) to twiv@microbe.tv or leave voicemail at Skype: twivpodcast

Emerging viruses?

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The term emerging virus was coined by scientists in the 1990s to describe the agent of a new or previously unrecognized infection. The term implies that emerging viruses are new; however this assumption is incorrect. New virus infections have been emerging for thousands of years, at least since the rise of agriculture 11,000 years ago. The development of agriculture and commerce provided the large populations needed to sustain human infections such as measles and smallpox.

Viruses probably (although we do not know for sure) appeared when living cells evolved, possibly even before. They subsequently infected multicellular forms of life and then mammals, which were present on the globe before humans. Humans then acquired virus infections from animals (an infection transmitted from animals to humans is a zoonosis). At some point the number of virus genomes and virion structures became established, and for the next millions of years, viruses evolved. It is unlikely that new viruses emerge de novo; rather they evolve from existing viruses.

Some examples serve to illustrate the origins of viruses. Comparisons of genome sequences of today’s members of the herpesvirus family has lead to the suggestion that these viruses arose 180-220 milllion years ago, possibly from ancestors of similar viruses that infect oysters and fish today. Smallpox virus may have emerged after an infection of humans with a gerbil poxvirus. Measles virus may have originated from infection of humans with an ancestor of a virus that today infects cows, rinderpest virus. It has been suggested that the virus ‘jumped’ from cows to humans about 5,000 years ago, when humans first began to domesticate cattle. Measles virus then spread throughout the Middle East and was then brought to the Americas by colonization and migration, where it had lethal effects on the Native Americans.

It is safe to say that all of the human viruses that exist today originated from a zoonotic infection. In some cases, related viruses still infect animals (e.g. measles and rinderpest virus). However, often the human virus has no known counterpart in animals. An example is the human pathogen, poliovirus. The ancestral poliovirus is not known, and there are currently no hosts for the virus other than humans. However, other members of the picornavirus family, of which poliovirus is a member, infect a variety of animals, and ancient versions of these viruses may have made the jump from animals to humans.

Two simple facts ensure that new human virus infections will continue to emerge from animal hosts. The first is the ability of viruses to produce huge numbers of progeny (billions and billions!) with a high level of diversity (mutation). The second is the fact that human and non-human animal populations continue to grow and interact. Put another way, humans are always finding new ways to acquire novel virus infections!

Viral evolution is a fascinating subject. A good place to start reading about it would be Principles of Virology, volume II, chapter 10.

TWiV #8 – HIV resistance, Google flu, measles in Gibraltar, viral batteries

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This Week in Virology #8 has been posted at www.microbe.tv/twiv.

Click the arrow above to play, or right-click to download TWiV #8

Vincent and Dick converse about warfare preventing immunization of 120,000 children in Afghanistan, bone marrow transplant curing AIDS patient, Google tracking flu, measles outbreak in Gibraltar, using viruses to make batteries, and small mosquitoes and Dengue.

Eradication of Measles in South Korea

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MMWR reports on 6 April 2007 that measles has been eliminated from South Korea. The history of measles in South Korea provides a useful example of how immunization practices need to be flexible to achieve their goals.

Measles vaccine was first introduced into South Korea in 1965, and was included in the national immunization program in 1983 as part of the measles, mumps, and rubella vaccine. Two doses were given to children at 12-15 months and 4-6 years. Despite this approach, measles continued to occur, exemplified by an epidemic in 2000-2001 of 55,000 reported cases and seven deaths. Most of these infections occurred in children, indicating that vaccination was not sufficient and that circulation of measles virus continued.

In 2001, South Korea declared a goal of establishing measles by 2005, and developed key strategies, including requiring two doses of measles vaccine for school entry by 7 years of age; carrying out vaccination campaigns among children 8-16 years to cover those who were missed at an earlier age; and including laboratory confirmation of reported cases in the surveillance program.

These strategies have been very successful. Before the eradication plan, there were multiple measles epidemics in South Korea, with annual cases ranging from two to 32,647. As of November 2006, no cases of measles have occurred, and international authorities have concluded that measles has been eliminated from the country.

Measles virus still circulates in much of the world, and therfore immunization must be continued in South Korea if the disease is to be kept in check. If there is any relaxation of immunization – likely given that the infection is no longer a problem – the virus is likely to spread again.

WHO has declared that after polio is eradicated, they will turn their efforts to measles virus. While the outcome of measles immunization programs in South Korea will surely be used to promote the global effort, it will be much more difficult to eradicate the disease globally.