Saturday, October 17, 2009

Simultaneous infections with multiple viruses - why are there so few studies?

For the past several years I’ve wondered about the clinical presentation of patients with multiple simultaneous infections.

The H1N1 outbreaks has brought this to mind again. We assume bad outcomes are the result of some odd combination of immune system and viral mutation, but what about the impacts of co-infection?

I’ve asked academic physicians about this question. I usually get a started look, then a statement that “common wisdom” is that the enhanced immune response to one infection makes a co-infection less likely*.

Turns out, though, that this question was researched 21 years ago ...

Am J Dis Child -- Abstract: Simultaneous Infection With Respiratory Syncytial Virus and Other Respiratory Pathogens, August 1988, Tristram et al. 142 (8): 834

… The presentation and subsequent course of respiratory syncytial virus (RSV) bronchiolitis may be atypical and unusually severe when simultaneous infection due to other pathogenic agents is present. During the past two years, nine of the 189 pediatric patients hospitalized with documented RSV infection were found to have the following simultaneous isolates from initial respiratory tract specimens: four adenovirus, four pneumococcus, one cytomegalovirus, and one Pneumocystis carinii. Noted complications attributable to the second pathogen included thrombocytopenia and anemia (cytomegalovirus), hepatitis and disseminated intravascular coagulation (adenovirus), and sepsis and osteomyelitis (pneumococcus). Three of the four patients with RSV and adenovirus died of severe respiratory failure despite mechanical ventilation; two of these patients received ribavirin therapy…

So 21 years ago it was shown that children with co-occurrent viral infections, such as adenovirus and RSV, could have more severe disease progression.

You’d think this study would have been widely cited, but you’d be wrong. A pubmed search on “simultaneous infection virus” returned no strong hits.

I’d love for someone who knows this area to explain why this hasn’t been studied further.

See also: Defining a disease: how often are atypical presentations due to multiple agents? (Feb 2006)

* When smart people say this they immediately get a worried look. In medicine “conventional wisdom” is often shorthand for “something that got into textbooks in the 1960s but, really, on inspection, has never been studied”.

Update 11/1/09: If one viral infection really prevented another, one could manage dangerous epidemics by giving everyone a cold.


Robbie said...

I'm from Missisippi, thus confused.
Where are the published long term safety studies of this H1N1 vaccine?
Peer Review?
My 10 year old daughter is suffering from multiple viral infections induced from our exposure during Hurricane Katrina. We were trapped, could not escape, and were thus swimming for our lives when our Gulfport, MS home imploded. She ingested copious amounts of sea water teaming with all mannor of exotic pathogens.
To date, 8 other children with similar exposures have presented with exact symptoms.
No one knows what to do.
Your Friend from the DarkSide

John Gordon said...

Hi Robbie,

There's a vast amount of undiscovered medicine, sometimes I think we've identified less than half the infections that afflict humans.

As for vaccine research -- I can't imagine a way to do long term studies on a vaccine that goes from creation to extinction in a matter of months. This makes vaccine surveillance very critical.