Navigation Links
Flu virus trots globe during off season
Date:9/20/2007

The influenza A virus does not lie dormant during summer but migrates globally and mixes with other viral strains before returning to the Northern Hemisphere as a genetically different virus, according to biologists who say the finding settles a key debate on what the virus does during the summer off season when it is not infecting people.

"Nobody really knows why flu is a winter disease in the temperate regions and more continuous in the tropics," says Edward Holmes, professor of biology at Penn State. "The big question is, Why is flu seasonal""

Flu infections in the Northern Hemisphere typically follow a familiar pattern. Some time before the start of the winter infection season, the virus evolves, changing enough to evade the previously primed immune system. Then, just before summer, the virus disappears, only to resurface the next fall with a completely different genetic makeup, ready to fool the immune system anew.

But little is known about what happens to the virus between two successive winters, or how and where it is able to sustain itself.

The key question, Holmes explains, is whether the virus settles into a dormant state waiting for the right cues of temperature and sunlight to reactivate, or whether it migrates to viral reservoirs in the tropics, from where it is later reintroduced.

It is thought that places in Southeast Asia, where humans and animals live in close proximity, might be the permanent melting pot where viruses continually circulate and exchange genetic information.

To test the migration theory, Holmes and Martha Nelson, graduate student at Penn State, and their colleagues at the National Institutes of Health, Lone Simonsen, Cecile Viboud, and Mark A. Miller, analyzed the influenza A virus genomes of 900 virus samples from New Zealand, Australia and New York state dating between 1998-2005.

Their findings, outlined in this month's issue of PLoS Pathogens, reveal that the genomes of 52 viruses from New York are closely related to viruses that circulate during the winter (April to October) in New Zealand and Australia. These mixed family trees of viruses from both the north and south suggest there is widespread viral traffic across the equator each season, which contributes significantly to new epidemics in both hemispheres, the researchers note.

"If the viruses had been dormant, samples from successive seasons in each region would only be closely related to other viruses of that same region," said Holmes, who is also affiliated with Penn State's Center for Infectious Disease Dynamics (CIDD). "The fact that they are, instead, interspersed clearly tells us that the viruses are seasonally migrating across both hemispheres."

However, it is still fully unclear where and when the viruses are evolving to beat the immune system. According to Nelson, the virus changes its entire genetic makeup somewhere during the summer off-season, and it likely does this in the tropics, where the virus is found year-round.

"But we cannot say for sure at this point. To test this theory, we need viral samples from the tropics," Nelson added. The authors anticipate that samples from these regions will become available in the next few years.

The researchers are also not sure why the virus seems to die out during summer and what exactly triggers its return.

"It could be anything from human migration, aspects of climate, levels of sunlight, seasonal susceptibility of people or a combination of all these and more factors. That is another big question," said Holmes, whose work is funded by the National Institutes of Health.

What is certain, the Penn State researcher noted, is that multiple viruses arrive in New York state each season. In a connected world where emerging viruses can spread globally very quickly, Holmes says that the best way to protect communities is to have an extremely good system of disease surveillance in place and to develop universal vaccines that can protect against all kinds of influenza virus.


'/>"/>

Contact: Amitabh Avasthi
axa47@psu.edu
814-865-9481
Penn State
Source:Eurekalert

Related medicine news :

1. Virus Level could Predict Cervical Cancer Risk
2. Ebola Virus - Outbreak Claims More Lives In Uganda.
3. Experimental treatment for Ebola Virus Shows promising results in mice
4. Virus Combats Brain Tumour
5. Virus killer
6. Minor mutations in HIV virus
7. Virus makes Hodgkin’s disease more deadl
8. Infertility in relation with virus
9. Birds breed viruses
10. Hidden influenza virus protein found
11. Pain Killers Keep the Virus Away
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:6/25/2016)... ... June 25, 2016 , ... Austin residents seeking Mohs surgery services, can now ... and to Dr. Russell Peckham for medical and surgical dermatology. , Dr. Dorsey brings ... The selective fellowship in Mohs Micrographic Surgery completed by Dr. Dorsey was under the ...
(Date:6/25/2016)... Oklahoma (PRWEB) , ... June 25, 2016 , ... ... both athletes and non-athletes recover from injury. Recently, he has implemented orthobiologic procedures ... Oklahoma City area —Johnson is one of the first doctors to perform the ...
(Date:6/24/2016)... ... June 24, 2016 , ... June 19, 2016 is World Sickle ... chronic pain and the benefits of holistic treatments, Serenity Recovery Center of ... Sickle Cell Disease. , Sickle Cell Disease (SCD) is a disorder of the red ...
(Date:6/24/2016)... ... June 24, 2016 , ... Comfort Keepers® of San Diego, ... and the Road To Recovery® program to drive cancer patients to and from their ... to ensure the highest quality of life and ongoing independence. Getting to and ...
(Date:6/24/2016)... (PRWEB) , ... June 24, 2016 , ... ... client, The Grove Investment Group (TGIG), has initiated cultivation and processing operations at ... Las Vegas and Pahrump, Nevada. , Puradigm is the manufacturer of a complete ...
Breaking Medicine News(10 mins):
(Date:6/24/2016)... , June 24, 2016 Dehaier Medical Systems ... "Company"), which develops, markets and sells medical devices and ... , signed a strategic cooperation agreement with Hongyuan Supply ... Supply Chain") on June 20, 2016, to develop Dehaier,s ... strategic cooperation agreement, Dehaier will leverage Hongyuan Supply Chain,s ...
(Date:6/24/2016)... Mass. , June 24, 2016   Pulmatrix, ... pharmaceutical company developing innovative inhaled drugs, announced today that ... Russell Investments reconstituted its comprehensive set of ... "This is an important milestone for Pulmatrix," ... will increase shareholder awareness of our progress in developing ...
(Date:6/23/2016)... Research and Markets has announced the addition of the ... report to their offering. ... failure, it replaces the function of kidneys by removing the ... the treatment helps to keep the patient body,s electrolytes such ... Increasing number of ESRD patients & substantial healthcare expenditure on ...
Breaking Medicine Technology: