Archive for May 16th, 2012

Measles — United States, 2011 MMWR

16 May, 2012

See on Scoop.itVirology and Bioinformatics from Virology.ca

“In 2000, the United States achieved measles elimination (defined as interruption of year-round endemic measles transmission) (1). However, importations of measles into the United States continue to occur, posing risks for measles outbreaks and sustained measles transmission. During 2011, a total of 222 measles cases (incidence rate: 0.7 per 1 million population) and 17 measles outbreaks (defined as three or more cases linked in time or place) were reported to CDC, compared with a median of 60 (range: 37–140) cases and four (range: 2–10) outbreaks reported annually during 2001–2010. This report updates an earlier report on measles in the United States during the first 5 months of 2011 (2). Of the 222 cases, 112 (50%) were associated with 17 outbreaks, and 200 (90%) were associated with importations from other countries, including 52 (26%) cases in U.S. residents returning from abroad and 20 (10%) cases in foreign visitors. Other cases associated with importations included 67 (34%) linked epidemiologically to importations, 39 (20%) with virologic evidence suggesting recent importation, and 22 (11%) linked to cases with virologic evidence of recent importation. Most patients (86%) were unvaccinated or had unknown vaccination status.

 

The increased numbers of outbreaks and measles importations into the United States underscore the ongoing risk for measles among unvaccinated persons and the importance of vaccination against measles (3).”

 

Amen!!  It is VERY revealing that so many cases were associated with imported virus infections – 90%!!  And almost HALF of those came from Europe, rather than from some developing country.

 

I thank Linda Stannard for the paramyxovirus EM

See on www.cdc.gov

Journal Virol Methods – A simple, rapid and efficient way to obtain infectious clones of potyviruses

16 May, 2012

See on Scoop.itVirology and Bioinformatics from Virology.ca

“The availability of an infectious cDNA clone is a prerequisite for genetic studies on RNA viruses. However, despite important improvement in molecular biology techniques during the last decades, obtaining such clones often remains tedious, time-consuming and rather unpredictable. In the case of potyviruses, cDNA clones are frequently unstable due to the toxicity of some viral proteins for bacteria. The problem can be overcome by inserting introns into the viral sequence but this requires additional steps in the cloning process and depends on the availability of suitable restriction sites in the viral sequence or adjunction of such sites by mutagenesis. Homologous recombination in yeast rather than in vitro restriction and ligation can be used to build infectious clones or other viral constructs. This paper describes how, by using recombination in yeast and fusion PCR, infectious intron-containing clones were obtained within a few weeks for two strains of watermelon mosaic virus (WMV, Potyvirus), whereas previous attempts using “classical” cloning techniques had failed repeatedly. Using the same approach, intronless infectious clones of two other potyviruses, zucchini yellow mosaic virus (ZYMV) and papaya ringspot virus (PRSV), were obtained in less than two weeks.”

 

I am a sucker for good techniques like this one: long ago I helped invent a technique for idiot-proof cDNA cloning of the 3′ of the genome (Pappu et a., J Virol Methods. 1993 Jan;41(1):9-20), and have kept a watchful eye on potyvirus genome cloning ever since – and it is a challenge, because they are >10kb in length.  This is an elegant solution to an old problem.

See on www.sciencedirect.com