Norovirus (Norwalk) and Rotavirus

[Astronuc]

A colleague was recently very ill and the illness was attiributed by the doctor to the Norwalk virus (aka 'stomach flu'). My sister, a pediatrician, informed me that cases of norovirus/rotavirus have increased. I have to wonder with all the flooding in the midwest, Gulf Coast (Katrina and Rita), and southeast US, if the contamination of regions with agriculture waste/runoff and municpal sanitary/sewear systems dramatically increased.

http://en.wikipedia.org/wiki/Norovirus (Caliciviridae)

Norovirus, an RNA virus of the Caliciviridae taxonomic family, causes approximately 90% of epidemic non-bacterial outbreaks of gastroenteritis around the world, and is responsible for 50% of all foodborne outbreaks of gastroenteritis in the US. . . .

http://en.wikipedia.org/wiki/Rotavirus (Reoviridae)

 

[Moonbear]

Those virii can spread fairly easily via casual contact as well (hence the difficulty in eradicating them on cruise ships once a passenger or two board already infected). They're the ones people usually call "stomach flu."

Without knowing more about it, I attribute it most likely to a more virulent strain or two evolving and spreading to those who have not been exposed previously. If that's what's going on, the incidence will slow down again as people get exposed and develop immunity.

 

[Astronuc]

With respect to immunity, I was surprised to read -

After infection, immunity to norovirus is not complete nor long-lasting.* There is an inherited predisposition to infection and people whose blood type can be detected in their saliva are more often infected.

*Cellular and Humoral Immunity following Snow Mountain Virus Challenge, Lisa Lindesmith, Christine Moe, Jacques LePendu, Jeffrey A. Frelinger, John Treanor, and Ralph S. Baric
http://jvi.asm.org/cgi/content/full/79/5/2900?view=long&pmid=15709009

I wonder if this is peculiar to RNA-based virii.

My colleague, who became ill, may have been exposed on an international airline flight.