# 3610
As if the H5N1 virus, with a CFR (Case Fatality Ratio) in humans of 60% wasn’t bad enough already, now a study indicates that it may induce some forms of brain damage in some of the survivors.
The study cited in today’s article was conducted on mice, but it showed that the H5N1 virus was neurotropic – or capable of infecting and damaging nerve cells.
First the report from Maggie Fox of Reuters, then a little more background information.
Bird flu causes Alzheimer's-like brain damage, study says
Tests on mice infected with H5N1 virus show lasting damage to nerve cells, including the brain
Maggie Fox
Washington — Reuters News Agency Last updated on Monday, Aug. 10, 2009 05:13PM EDT
Survivors of bird flu, and perhaps other influenza viruses, may not be out of the woods once the fever and cough are gone: Animal studies suggest the virus may damage the brain and cause Alzheimer's and Parkinson's disease.
The tests on mice show that the H5N1 virus can get into the brain, causing damage that resembles Parkinson's and Alzheimer's in humans, the researchers wrote in the Proceedings of the National Academy of Sciences.
“Our results suggest that a pandemic H5N1 pathogen, or other neurotropic influenza virus, could initiate central nervous system disorders of protein aggregation including Parkinson's and Alzheimer's diseases,” Richard Smeyne of St. Jude Children's Research Hospital in Memphis, Tenn., and colleagues wrote.
There have been rumors over the years of occasional neurological manifestations accompanying H5N1 infection, with the most famous case being that of Jones Ginting – the only survivor of the Karo cluster in Indonesia in 2006.
We’ve seen precious little in the way of long-term follow up of bird flu survivors. Something that would be of considerable interest, I should think, to researchers.
During the 1918 pandemic, and the decade that followed, more than a million people around the world were afflicted by a mysterious neurological disorder called Encephalitis Lethargica (EL), which some researchers believe may have been precipitated by the influenza virus.
Other scientists have linked EL with a post-streptococcal immune response, or believe it was an autoimmune response, and dismiss the link with the 1918 pandemic. The cause remains a mystery.
Other forms of neurological symptoms were also reported in the years (and decades) following the 1918 pandemic, leading some researchers to question whether or not it might be a part of some long-term sequelae of the virus.
And just last month the CDC’s MMWR (July 23rd issue) reported on 4 pediatric patients with the novel H1N1 virus who presented with neurological symptoms including unexplained seizures and altered mental status.
Neurologic Complications Associated with Novel Influenza A (H1N1) Virus Infection in Children --- Dallas, Texas, May 2009
Neurologic complications, including seizures, encephalitis, encephalopathy, Reye syndrome, and other neurologic disorders, have been described previously in association with respiratory tract infection with seasonal influenza A or B viruses (1--2), but not with novel influenza A (H1N1) virus.
On May 28, 2009, the Dallas County Department of Health and Human Services (DCHHS) notified CDC of four children with neurologic complications associated with novel influenza A (H1N1) virus infection admitted to hospitals in Dallas County, Texas, during May 18--28.
And it should be noted that even seasonal influenza has been linked to very rare neurological symptoms. The editorial note from the MMWR stated that:
Considering that clusters of influenza-associated encephalopathy in children have been reported during previous community outbreaks of seasonal influenza (1--2) and that children appear to be infected with novel influenza A (H1N1) virus more frequently than adults (3), additional neurologic complications in children are likely to be reported as the pandemic continues.
Clinicians should consider influenza associated encephalopathy in the differential diagnosis of children with ILI and seizures or mental status changes, and remain aware of the potential for severe neurologic sequelae associated with seasonal or novel influenza A (H1N1) virus infection.
The incidence of neurological involvement with most influenza viruses appears to be quite low, although it is likely that some strains of the virus (such as the H5N1 virus) are more capable of infecting nerve cells than others.
Obviously, this is area where a lot more research is needed.
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