CDC also seeing more REGULAR flu cases than normal

[Siegfried X]

Not only is the new flu spreading, but the regular seasonal flu is infecting many more people than is normal for this time of year.

U.S. health officials are seeing a surprisingly high number of cases of ordinary, seasonal flu at a time when the flu season typically peters out.

About half of people recently testing positive for the flu have the new swine flu virus, Dr. Daniel Jernigan of the Centers for Disease Control and Prevention in Atlanta said Friday.

The rest have seasonal flu, which is still causing widespread or regional illness in about two dozen states, "something that we would not expect at this time," he said. "We would be expecting the season to be slowing down or almost completely stopped."

The higher numbers of seasonal flu cases do not seem to be just because health officials are looking harder this year because of worries about swine flu...

"The [new] H1N1 virus is not going away," Jernigan said. The virus "appears to be expanding throughout the United States" and poses "an ongoing public health threat," he said.

Swine flu continues to affect more younger people ? those ages 5 to 24 ? and CDC is still seeing relatively few cases in older people.

"That may be just a matter of time" until the virus spreads to that population, or it may prove to be a difference in the virus or its effect on various groups, he said.

CDC seeing more regular flu cases

 

[wotan]

Re: CDC also seeing more REGULAR flu cases than normal

Are they typing these seasonal flus? I havent seen it yet.

 

[Siegfried X]

Re: CDC also seeing more REGULAR flu cases than normal

Information about flu types, etc. is in the CDC's weekly flu report:

Weekly Flu Report

 

[Skatman]

Re: CDC also seeing more REGULAR flu cases than normal

Dr. Niman posted on this issue yesterday and if I remember correctly he said that if they are just typing it will show up a influenza A (H1N1) and they are calling it seasonal flu.

I think if they are not running a PCR how do they know, if you look at the results from week 13 you will see that the number of seasonal influenza A (H1) and H(3) had been declining over the previous 4 weeks and think that it would be unusual for seasonal influenza A to pick back to pick back up after then.

http://www.cdc.gov/flu/weekly/weeklyarchives2008-2009/weekly13.htm

 

[AlexanderSJones]

Re: CDC also seeing more REGULAR flu cases than normal

There is a second reason why seasonal flu may spike, and that is coinfection.

A primary infection with the H1N1 flu increases the risk of acquiring a second, distinct strain of flu (H3N2 or bacteria, for example).

 

[wotan]

Re: CDC also seeing more REGULAR flu cases than normal

Are there enough differences between Influenza A and B to preclude reassortment or recombination between those two species? Or would any virion that results be, effectively, unfit for any future replication?

 

[AlexanderSJones]

Re: CDC also seeing more REGULAR flu cases than normal

Good question -- there is a paper on this coming out soon. I think a general rule would be to say the closer the strains are in homology, the more likely they are to swap genetic material. . . So swine flu recombining or reassorting with seasonal H1N1 or H3N2 would be much more likely than influenza B.

------------
1: Int J Infect Dis. 2009 May;13(3):e127-8. Epub 2008 Oct 11.Click here to read Links
Characterization of an influenza A and influenza B co-infection of a patient in a long-term care facility with co-circulating influenza A and influenza B.

------------

Also, see:

1: Arch Virol. 2008;153(4):651-5. Epub 2008 Feb 5.
Coinfection of avian influenza virus (H9N2 subtype) with infectious bronchitis live vaccine.

Abstract

Avian influenza virus of H9N2 subtype is pathotyped as a non-highly pathogenic virus. However, frequent incidences of avian influenza of high mortality that are caused by H9N2 viruses have been observed in broiler chicken farms in Iran and some other Asian countries. Coinfections or environmental factors may be involved in such cases. Infectious microorganisms have been implicating in taking part in the cases of coinfection. We studied the effect of experimental coinfection of H9N2 avian influenza virus with infectious bronchitis live vaccine, which is used extensively in chicken farms in Iran. Clinical signs, gross lesions, viral shedding and mortality rate of the experimentally infected birds were examined. Coinfection of infectious bronchitis live vaccine and H9N2 avian influenza virus led to an extension of the shedding period of H9N2 virus, increasing the severity of clinical signs and mortality rates, causing macroscopic lesions in the embryos.

http://www.ncbi.nlm.nih.gov/pubmed/18247102

 

[wotan]

Re: CDC also seeing more REGULAR flu cases than normal

Good question -- there is a paper on this coming out soon. I think a general rule would be to say the closer the strains are in homology, the more likely they are to swap genetic material. . . So swine flu recombining or reassorting with seasonal H1N1 or H3N2 would be much more likely than influenza B.

Oh I'll grant that. I was curious when I first started seeing a taxonomic classification of viruses being used. When I was in school there was no mention of such things, so I don't know if it wasn't widely adopted yet or they just didn't cover it in our textbooks.

It doesn't look like it is (widely?) taken further back the families, and even at the level there doesn't seem to be much in common across the members. So even within the three(?) species of influenzavirus I am not sure how much of the genetics is shared.