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The complexity of the HIV virus has increased through constant recombination. There are already many subtypes of the HIV-1 strain, and the diversity is growing. Even strains of the same subtype may now differ by up to 20 percent.
This knowledge is imperative in the quest for an AIDS vaccine. If a vaccine can be created, it's still unclear how much diversity it will be able to cope with.
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Scientists say it will be important to examine whether chimpanzee predation on smaller monkeys has led to additional SIV acquisitions, and possibly coinfection and recombination with SIVcpz, and whether the resulting chimpanzee-adapted SIVs are more likely to infect humans.
"The major difference between SIV infection of chimpanzees and HIV infection of humans is that chimpanzees are not known to develop any disease symptoms," said Sharp. "Given the very close genetic relationship between chimpanzees and humans, this prompts the question whether chimpanzees have co-evolved with their virus to reach this non-pathogenic association."
Jumping and Recombining
Many, though not all, human viruses originated by cross-species transmission. On the list of viruses that have jumped from animals to humans are measles, influenza A, Ebola, HIV, SARS, dengue, and many others.
Some appeared in the last century; others emerged thousands of years ago and stayed. A few have always been with us, infecting our ancestors before they evolved to become humans.
"Almost all the human viruses have this kind of counterparts in animals, so they must have a common origin," said Lai.
The influenza A virus jumped into humans from birds, perhaps using pigs as a "mixing vessel," to create devastating pandemics in 1918, 1957, and 1968. Ebola hides in an (as yet unidentified) animal from where it jumps to humans. SIVcpz jumped from chimpanzees to humans at least three times.
"Advances in the ease of finding and characterizing viral genome sequences are having a major impact on our understanding of the diversity of human viruses and of their relatives infecting other species," said Sharp.
After jumping species, viruses can recombine with other viruses that have made the same jump, or with divergent strains already existing in the host, sometimes creating new hybrid viruses that may in some cases increase virulence.
Measles is one virus where recombination probably did not happen. Measles infections only last about two weeks, and generally there is only one strain common in a geographic area. So the opportunity for two viruses to meet may be limited.
Exotic Pets
Another virus that jumped species is monkeypox. Health officials in Wisconsin, Illinois, and Indiana recently reported the first outbreak of monkeypox in the Western Hemisphere. This is a rare viral disease that occurs primarily in the rain forests of central Africa.
The disease is called monkeypox because it was discovered in laboratory monkeys in 1958. Studies later showed evidence of infection in ground squirrels, which may be a natural host for the virus.
Infection with the virus results in a rash similar to smallpox, but less infectious. It's usually not fatal. Symptoms include fever, headache, muscle aches, backache, and swollen lymph nodes.
The people who became ill in northern United States reported close contact with ill prairie dogs. Health officials believe the prairie dogs contracted the monkeypox virus from infected Gambian giant rats, which were imported from Africa and housed in the same animal-holding facility as the prairie dogs.
"When we expose ourselves to exotic animals, there is always a risk of being exposed to something unknown," said Lai.
Scientists believe the encroachment by humans on nature also increases the spread of infectious diseases. The SIVcpz strain jumping from chimpanzees to humans likely occurred when humans hunted and butchered chimps for "bush meat," something humans have done for centuries.
Increased human populations have increased the chances of a virus successfully propagating among humans once it has made the jump. The SIVcpz strain was probably transmitted to humans in previous centuries, but never established a substantial enough transmission chain among humans to cause a large outbreak.
"When we perturb the existing peace between human beings and nature, we are opening a Pandora box, which may contain many surprises," said Lai.
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Cards?
Travelling?
Sleepy?
Wanna play Wii?
It was a night, just like any other night...
Did you tell me to stay cool until after school?
Going down to the station? Got your suitcase in your hand...
Deal the cards, son, just deal the cards...
Call me...
I thought we could go to a film after the game...
Marianne Faithfull- As Tears Go By 1965
some cards...
Rods?
Rolling Stones- Angie
女子高生
What is going on in the music scene?
Cut the cards, Sharpie!
Last Gasp Cafe 14...
Get up and go? Where to?
Gwen Stephani- The Great Escape...
Coffee? Orange juice only from 10.30, Dude...
Last Gasp Cafe 13...
I have GOT to lose weight...
Bob Dylan- Like a Rolling Stone 1966
SERIOUSLY, I HAVE to lose weight...
Requiem for Erika Ortiz :^: Broken Road
Have to DO something about my skin...
Pink Floyd: The Mind's Eye
who is buying?
Lady so Far :-: for Tyra Banks
better make some money...better call home...
C.C.Catch - Backseat of your Cadillac
puffshop
just then the computer started to play up...
Last Gasp Cafe 8
Good morning...
Jim Carrey - Standup Routine - Comedy Store (1996)
I've got this, like, really oily skin...
What was that?
Last Gasp Cafe 4...
Good deed done for the day... every day...like a roller coaster...
Last Gasp Cafe 15: Concert for Donnie Darko
I tried to lose weight in a New York minute and nearly got lost...
She read the cards slowly...
Last Gasp Cafe 2...
I went to bed with a book...
女子高生
To sleep perchance to...
Cheltenham is on...
BQ on B :-: Brazilian Queen on Beale St
The Lady was talking to Tee about opportunities on the net...
but Throg was dreaming about a back rub...
Throgmorton woke up and thought about an ipod...
Colin for Mark...
Last card, Freddie, Last card...
Chickenman woke up thinking about Bob Greene and Oprah...
Rolling Stones, Gimme Shelter(Pop Go the Sixties) 1969
I thought about my business opportunities...don't count your money till the dealings done...
Sweet Miss Jay- Angelina Jolie...
I attended to what was left of the business and did my Sporting Index chores...
I was bored so I called my business advisor on Dialaphone...
she mentioned Zwinky...
I was like,lol, what about Zylom...
Rolling Stones- Sympathy for the devil. Live in Rio 2006
cards,money,cards,money...
things got serious and we talked about Finance Box Houses...
and Finance Box Student Loans...
Showbuzz rox she shouted...
I told her about Bonprix, classy? well yes...
don't forget Anona, Big Sun, Barstow, San Bernadino...and don't forget Yves...
we talked about lost souls we shared and she told me how we might find them on Reunion...
skimming cards on the Riverboat?
Voip? for sure I said...
then we climbed the Lending Tree together...
take a chance on Coral?
me, I'm lost in space...SATNAV for space cowboys like you, she murmured...
we played at the Red Casino...
we flew Siesta...
we met each other again on Yahoo Personal...
Dating?
just having fun on Gameplay actually...
we listened to Attic Jam...
we got right into The Hedrons...
and how about the new album from da Red Hot Chilli Peppers...
you can buy these with a Post Office Credit Card she told me over lunch...
and in the afternoon we flew away on HLX...
I noticed that she wore Nikes...
we booked a lovely place to stay through Cottages...
Radio Story aka The Story Continues...
she looked stunning in her Contessa gear...
Deftones at Taste of Chaos - RX Queen w/ Street Drum Corp
a card up your sleeve, one in your cuff...
we listened in the dark to Beck...
she declared that she would vote for Hilary Clinton...
me, I want more of Mate-dating...
we discussed our bodies and Hoodia...
then she told me about another way to lose weight...
Phentrazine - Now Available Without a Prescription
me being more of a car person I clicked on Auto Loan...
Changing Chairs
she wanted money for other things so she clicked on Ocean Financial...
We both decided that discretion was the better part of valour and we looked at the Privacy Credit Card...
Sweet Killer Love
thought about Global Travel...
and looking good the French way...
U2 and Mary J Blige- One, Madison Square Garden 10-8-05
we talked a little about a career in Criminal Justice...
but what really got us going was the thought of a Bahamas Cruise- the Anna Nicole Smith Tour? Well...
very last card...
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