This is SCIENCE IN THE NEWS in VOA Special English. I'm Bob Doughty. And I'm Faith Lapidus. Summer is a busy time for travel. Today, we discuss ideas about how to stay healthy on a long trip.For years, people have wondered whether they are safe from germs when they travel in small, enclosed areas. They worry about close contact with others who may be sick.
The current spread of a swine influenza virus has added to these concerns. Recently, the World Health Organization raised its warning about the new H1N1 virus to its highest level. W.H.O. Director-General Margaret Chan declared the sickness a pandemic – a disease that has spread to many nations. Given this information, many people want to know how safe is it to travel?
The answers people are getting may seem conflicting. For example, a W.H.O. statement urged nations not to close their borders or limit trade and travel. Director-General Chan said cases are generally mild for most people. Still, W.H.O. officials continue to report new cases across the world.
In the past, the W.H.O. and experts with America's Centers for Disease Control and Prevention noted guidance for disease spread on airplanes. The experts said you could get infected only if you sit within two rows of someone who is sick. That would be a distance of up to three meters from the sick person. And this was true only if you sat there for more than eight hours.
But a travel-health expert says this guidance may not be helpful for swine flu. Mark Gendreau works at the Lahey Clinic Medical Center in the American state of Massachusetts. He suggests steps that could help prevent getting swine flu on an airplane.
His advice includes keeping the airflow over your seat on the "low" position. The doctor says you should point the device so the flow of air is just in front of your face.
Infection can spread through touching an infected surface and then touching your eyes, nose or mouth. Doctor Gendreau suggests cleaning your hands with soap and water, or using hand-sanitizer wipes. These products should contain at least fifty percent alcohol. In addition, he said you may want to cover your face with a mask. Most importantly, avoid traveling when you are sick.
Clearly, most people do not get sick while taking long trips. But something else might interfere with your travel plans. You could be placed in medical isolation if someone you traveled with on a plane is suspected of having swine flu.
The top official of an American city recently had this experience. New Orleans Mayor Ray Nagin, his wife and a security guard spent several days in a hospital-like center in Shanghai, China. At the time, they were on their way to Australia. Mayor Nagin was preparing to speak there. But they were detained because of someone who sat near them on their arriving flight. The person was suspected of having swine flu. The Nagins did not get sick.
Students from a high school in Maryland had a similar experience. On a recent visit to China, the students had to spend several days in hotel rooms in the city of Kaili. They were barred from leaving their rooms because someone on their flight was suspected of having the flu. Tests later proved that the suspicion was wrong.
The students lost several days of sight-seeing. But one girl said she was still glad she made the trip.
Many other people share her feeling. One man from Maryland says he has planned a trip to Ireland for many years. He wants to visit the burial places of his grandparents. He says it will take more than a pandemic to keep him from making his trip.
Technology on most airplanes might make you feel safer about air travel. The United States Federal Aviation Administration says most large passenger planes now use HEPA filters. The devices are designed to remove dangerous particles from the air.
The letters H-E-P-A represent the words High Efficiency Particulate Air. HEPA filters capture almost all particles in the air that are zero point three microns in size or larger.
America's Atomic Energy Commission developed HEPA filters many years ago. The goal was to protect workers who were developing the atomic bomb. The first HEPA filters removed radioactive particles from the air. Today, the filters clean the air in planes.
The Centers for Disease Control says HEPA filters are effective in clearing the air of many particles that cause disease. Makers of the devices say they kill bacteria and viruses because they help to remove the wetness that germs need to survive. But HEPA filters cannot remove disease-causing particles smaller than zero point three microns. These will continue to move around in the air and can infect people.
On a passenger cruise ship, fresh air is available on decks and in other places above sea level. A spokesperson for the Cruise Lines International Association says other air quality depends on the requirements of the nation where a ship was built.
Experts say people should know about other health concerns that can strike when traveling by air. One of these is hypoxia. It results from a lack of oxygen to the brain. Experts say the body begins losing oxygen minutes after an airplane leaves the ground.
The air pressure in a plane during flight is lower than at sea level. This makes it more difficult for the body to effectively use the same amount of oxygen as it would on the ground. Fewer oxygen molecules cross the tissues in the lungs and reach the bloodstream.
The result is a five to twenty percent drop in the amount of oxygen in the blood. This reduces the amount of oxygen that reaches the organs of the body.
One effect of this lack of oxygen to the brain is a headache. When this happens, the heart attempts to fix the situation by beating harder and faster. This can make the traveler feel tired.
These signs of hypoxia are not dangerous in a healthy person. But a drop in oxygen levels can cause a health emergency in people with heart or lung problems. They might lose consciousness or even suffer a heart attack.
Experts say use of cigarettes and alcoholic liquids also reduces the body's ability to use oxygen. So they suggest that people not drink alcohol or smoke cigarettes either before or during a flight. They also say persons with heart or lung problems should seek advice from their doctor before flying.
Another problem for travelers can be a condition called deep vein thrombosis. A thrombosis is a blood clot -- a condition in which some blood thickens and blocks the flow to the heart. Blood clots can kill if they move to the heart and lungs and stop needed oxygen from reaching those important organs. This is known as a pulmonary embolism.
The World Health Organization says passengers who sit still for four or more hours face a greater risk of developing blood clots. But it says only one in six thousand people develop deep vein thrombosis.
Last week, Harvard University researchers reported that people who travel are three times more likely than others to develop deep vein thrombosis. The researchers examined information from fourteen earlier studies. They found the longer the trip, the greater the threat of deep vein thrombosis. They even found a measurable increase in the condition for every two hours sitting in a car.
Experts say the chance of a clot also increases if a person does not drink enough water. They say passengers who sit for hours need to drink plenty of water -- not liquids that contain alcohol or caffeine. Passengers should also increase blood flow to the legs. The doctors suggest covering your legs with support stockings and walking every hour or so during the trip. Or, at least move your legs and feet.
Doctors say anyone with pain, swelling or red skin on a leg during or after a long trip may have a blood clot. Anyone with such signs should see a doctor as soon as possible. The condition many times can be treated with drugs that thin the blood and stop the clot from moving through the body.
This SCIENCE IN THE NEWS was written by Nancy Steinbach and Jerilyn Watson. Our producer was Brianna Blake. I'm Bob Doughty. And I'm Faith Lapidus. Read and listen to our programs at voaspecialenglish.com. Join us again next week for more news about science in Special English on the Voice of America.