Translate the text into Ukrainian. Influenza is a common infection of the nose and throat, and sometimes the lungs

Influenza is a common infection of the nose and throat, and sometimes the lungs. The cause is a virus that passes from one person to another. The virus spreads through the air when an infected person expels air suddenly.

Influenza develops after the virus enters a person's nose or mouth. The flu causes muscle pain, sudden high body temperature, breathing problems and weakness. Generally, most people feel better after a week or two. But the flu can kill. It is especially dangerous to the very young, the very old and those with weakened defenses against disease.

The World Health Organization says the influenza virus infects up to five million people around the world each year. Between two hundred fifty thousand and five hundred thousand people die every year from influenza.

Medical experts have recognized for some time that people become infected with influenza during the winter months. But they did not really know why until recently.

American researchers say they now know why the influenza virus spreads in the winter and not in the summer. They say it is because the virus remains in the air longer when the air is cold and dry.

Researchers in New York carried out twenty experiments with guinea pigs to investigate how the virus spreads. First, they confirmed that the guinea pigs could develop the flu and pass it on to others. The researchers then placed the animals in areas where the virus was present in the air. Then they changed the temperature and humidity levels of their environments. Humidity is the amount of wetness in the air.

The researchers found the virus spread the most when the temperature was about five degrees Celsius and the humidity was twenty percent. Few of the guinea pigs developed influenza as the temperature increased. The virus stopped spreading completely at thirty degrees Celsius and eighty percent humidity. The researchers also found that the animals spread the virus among themselves nearly two days longer when the temperature was low.

The researchers say, however, that people should not stay in warm places all the time in cold weather to avoid the flu. They say the best way to prevent the sickness is to get yearly injections of a vaccine that prevents influenza.

Medical experts have identified three major kinds of influenza. They call them type A, B and C. Type C is the least serious. People may not even know they have it. But researchers study the other two kinds very closely. Viruses change to survive. This can make it difficult for the body to recognize and fight an infection.

A person who has suffered one kind of flu cannot develop that same kind again. The body's defense system produces antibodies. These substances stay in the blood and destroy the virus if it appears again. But the body may not recognize a flu virus that has even a small change.

Each year, researchers develop vaccines to prevent the spread of the flu virus. The World Health Organization holds meetings in which experts discuss what kinds of flu viruses to include in the next vaccine.

Historical records have described sicknesses believed to be influenza for more than two thousand years. The Roman historian Livy described such a disease attacking the Roman army. People in fifteenth century Italy thought sicknesses were caused by the influence of the stars. So they called it, "influenza."