instruction:
Generate an explanation for the given claim using the provided supporting material from the paragraph. Please consider the following points while generating an output. 1) The claim will always have supporting proof in the paragraph, and the paragraph will have a clear point of view supporting the claim. 2) There can be instances where direct correlation to the claim is not available. Make use of the sentences in the paragraph to provide a corresponding output supporting the claim. 3) The explanation should be at least one and at most twelve sentences long.
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Paragraph: News outlets report the Centers for Disease Control and Prevention says it was notified on Oct. 1 that a flight attendant had a confirmed case. The Mecklenburg County Health Department says it contacted 18 Charlotte-area passengers who were on the American Airlines flight Sept. 21 from San Francisco to Charlotte. Spokeswoman Rebecca Carter says those passengers have since been vaccinated. American Airlines released a statement saying it's in close contact with the CDC and public health officials and will coordinate with them on any required health and safety related measures. Hepatitis A is a liver disease caused by contaminated food or water. Claim: Flight attendant may have exposed passengers to Hepatitis A.
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Health officials in North Carolina say more than a dozen people may have been exposed to hepatitis A on a recent flight.

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Paragraph: An early barrage of illness in the South has begun to spread more broadly, and there's a decent chance flu season could peak much earlier than normal, health officials say. The last flu season to rev up this early was in 2003-2004 a bad one. Some experts think the early start may mean a lot of suffering is in store, but others say it's too early to tell. "It really depends on what viruses are circulating. There's not a predictable trend as far as if it's early it's going to be more severe, or later, less severe," said Scott Epperson, who tracks flu-like illnesses for the U.S. Centers for Disease Control and Prevention. There are different types of flu viruses, and the one causing illnesses in most parts of the country is a surprise. It's a version that normally doesn't abound until March or April. That virus generally isn't as dangerous to older people good news, since most flu hospitalizations and deaths each winter occur in the elderly. However, such viruses can be hard on children and people younger than 50. Louisiana was the first state to really get hit hard, with doctors there saying they began seeing large numbers of flu-like illnesses in October. Children's Hospital New Orleans has already seen more flu cases this fall than it saw all of last winter, said Dr. Toni Gross, the hospital's chief of emergency medicine. Last month was the busiest ever at the hospital's emergency department. Officials had to set up a triage system and add extra shifts, Gross said. "It is definitely causing symptoms that will put you in bed for a week," including fever, vomiting and diarrhea. But the hospital has not had any deaths and is not seeing many serious complications, she said. Health officials tend to consider a flu season to be officially underway when for at least three weeks in a row a significant percentage of U.S. doctor's office visits are due to flu-like illnesses. That's now happened, CDC officials said this week. The agency on Friday estimated that there have already been 1.7 million flu illnesses, 16,000 hospitalizations, and 900 flu-related deaths nationally. The most intense patient traffic had been occurring in a six states stretching from Texas to Georgia. But in new numbers released Friday, CDC officials said the number of states with intense activity rose last week to 12. Flu is widespread in 16 states, though not necessarily at intense levels in each, the CDC said. Last flu season started off as a mild one but turned out to be the longest in 10 years. It ended with around 49,000 flu-related deaths and 590,000 hospitalizations, according to preliminary estimates. It was bad, but not as bad as the one before it, when flu caused an estimated 61,000 deaths and 810,000 hospitalizations. Those 2017-2018 estimates are new: The CDC last month revised them down from previous estimates as more data including actual death certificates came in. In both of the previous two flu seasons, the flu vaccine performed poorly against the nasty predominant virus. It's too early to say how well the vaccine is performing right now, Epperson said. Epperson said there's a chance the flu season will peak this month, which would be unusually early. Flu season usually doesn't hit fever pitch until around February. The early start suggests a lot Americans may be sick at the same time, said Dave Osthus, a statistician who does flu forecasting at Los Alamos National Laboratory. "This could be a precursor to something pretty bad. But we don't know," he said. Gross is pessimistic. "I, personally, am preparing for the worst," she said. ___ The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute's Department of Science Education. The AP is solely responsible for all content. Claim: US flu season arrives early, driven by an unexpected virus.
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The U.S. winter flu season is off to its earliest start in more than 15 years.

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Paragraph: Scientists said on Wednesday many Tibetans possess a rare variant of a gene involved in carrying oxygen in the blood that they likely inherited from an enigmatic group of extinct humans who interbred with our species tens of thousands of years ago. It enables Tibetans to function well in low oxygen levels at elevations upwards of 15,000 feet (4,500 meters) like the vast high plateau of southwestern China. People without this variant would be apt to develop thick blood, leading to high blood pressure, heart attacks, strokes, low-birth-weight babies and higher infant mortality. This version of the EPAS1 gene is nearly identical to one found in Denisovans, a lineage related to Neanderthals - but is very different from other people today. Denisovans are known from a single finger bone and two teeth found in a Siberian cave. DNA testing on the 41,000-year-old bone indicated Denisovans were distinct from our species and Neanderthals. "Our finding may suggest that the exchange of genes through mating with extinct species may be more important in human evolution than previously thought," said Rasmus Nielsen, a computational biology professor at the University of California, Berkeley and the University of Copenhagen, whose study appears in the journal Nature. Our genome contains residual genetic fragments from other organisms like viruses as well as species like Neanderthals with which early modern humans interbred. The researchers called their study the first to show that a gene from an archaic human species has helped modern humans adjust to different living conditions. "Such exchange of genes with other species may in fact have helped humans adapt to new environments encountered as they spread out of Africa and into the rest of the world," said Nielsen. Asan Ciren, a researcher with China's BGI genomics center, added, "The genetic relationship or blood relationship between modern humans and archaic hominins is a hot topic of the current paleoanthropology." The researchers said early modern humans trekking out of Africa interbred with Denisovans in Eurasia en route to China. Their descendants harbor a tiny percentage of Denisovan DNA. Genetic studies show nearly 90 percent of Tibetans have the high-altitude gene variant, along with a small percentage of Han Chinese, who share a common ancestor with Tibetans. It is seen in no other people. The researchers conducted genetic studies on 40 Tibetans and 40 Han Chinese and performed a statistical analysis showing that the gene variant almost certainly was inherited from the Denisovans. The gene regulates production of hemoglobin, a protein in red blood cells that carries oxygen. It is turned on when blood oxygen levels drop, stimulating more hemoglobin production. At elevations above 13,000 feet (4,000 meters), the common form of the gene boosts hemoglobin and red blood cell production, causing dangerous side effects. The Tibetans' variant increases hemoglobin and red blood cell levels only modestly, sparing them these effects. Claim: Gene from extinct human species fortifies high-altitude Tibetans.
answer:
How do Tibetans thrive in high-altitude, low-oxygen conditions that would make others wither? Well, they may have received some help from an unexpected source.