Health officials around the world are concerned about rising numbers of new coronavirus cases. But another highly infectious virus will soon be returning to Earth's Northern Hemisphere. That virus is influenza, commonly called the flu.

The United States Centers for Disease Control and Prevention estimates that about eight percent of Americans get influenza each year. The flu season takes place during the winter months. During that time, hundreds of thousands of people are sick enough with the flu to be admitted to hospitals.

This year, with the U.S. health system already dealing with COVID-19, medical experts are concerned about the return of the flu.

"We really, really want to emphasize the potential for disaster," said Jeanne Marrazzo. She directs the Division of Infectious Diseases at the University of Alabama at Birmingham and is a member of the Infectious Diseases Society of America's board of directors.

Experts are urging Americans to get the flu vaccine in an effort to ease the pressure on healthcare workers and hospitals.

The Centers for Disease Control (CDC) estimates that as many as 61,000 people die from influenza in the United States each year. It adds that U.S. hospitals treat as many as 810,000 Americans infected with the flu. People older than age 65 or those who have other health conditions are at greatest risk.

But the United States and much of the world is already fighting the novel coronavirus. The Johns Hopkins University Coronavirus Resource Center reports that nearly 200,000 Americans have died from COVID-19.

"We still are on what we think of as a razor's edge with regard to COVID," Marrazzo noted.

As summer comes to an end, "I expect it to get worse," said Michael Mina. He is an assistant professor of epidemiology at Harvard T. H. Chan School of Public Health.

Rates of many respiratory diseases, including flu and the common cold, increase in autumn and winter. The reasons are not entirely understood, but the viruses that cause the diseases may spread more easily in colder, drier air than in warmer, wet weather.

Also, people spend less time outside the home in the winter and more time close to each other, often breathing the same air. Children may pass around viruses more readily in schools than when they are home for the summer and spending time outside.

It remains unclear how much the weather affects the spread of the coronavirus. Scientists are actively studying the question. The coronavirus is related to other viruses that cause the common cold. Mina noted, "what we see with those viruses is that come October, November, December they skyrocket."

"I hope that for some reason this virus behaves differently, but I don't anticipate that it will," he added.

Officials: flu shots are very important

While a safe coronavirus vaccine is in the future, U.S. health officials are urging everyone to get a flu shot as soon as possible.

In most years, not even half of all adult Americans get vaccinated. The rate is even lower among minority groups. That is in part because getting a flu shot does not guarantee protection against the virus.

"Influenza vaccine in a good year is generally between 40 and 60 percent effective," said Walter Orenstein associate director of the Emory University Vaccine Center in Georgia. "Not perfect, but it's a lot better than zero percent effective, which is (what you get) if you don't get vaccinated."

The vaccine helps, even if it does not stop the infection, noted William Schaffner. He is an infectious diseases expert at Vanderbilt University in Tennessee.

"Even if you get influenza after you've had the vaccine, that illness is likely to be less severe," he said. "You're less likely to need to go to the emergency room, less likely to be hospitalized, less likely to die."

That is good news for patients, and it also helps the health care system. "The last thing we need is a huge surge of flu cases now," he added.

Vaccine manufacturers are expecting to produce a record supply of nearly 200 million doses of flu vaccine this year. However, the conditions making flu shots so important are the same conditions that make them harder to provide to everyone, Schaffner noted.

Fewer people will get flu shots at work this year because more people are working from home. Many public health centers are closed or are working on COVID-19 cases. Many people are avoiding doctor's offices completely out of fear of getting infected there.

Drug stores and supermarkets are still good places to get vaccinated, noted Jeanne Marrazzo of the Infectious Diseases Society of America. "People will probably need to be perhaps a little bit more creative," she said.

The steps taken to limit the spread of the coronavirus, such as covering one's face, hand washing and social distancing, all seem to work against the flu.

The World Health Organization says these measures are likely to have led to the mild flu season currently coming to a close in the Southern Hemisphere.

I'm Ashley Thompson.

And I'm Mario Ritter Jr.

Steve Baragona reported this story for VOANEWS. Mario Ritter Jr. adapted it for Learning English. George Grow was the editor.

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hemisphere – n. a half of the Earth, usually divided between the northern and southern halves

emphasize –v. to give special importance or attention to something

razor's edge –n. a dangerous position in which two different things are carefully balanced

respiratory –adj. related to breathing and the lungs

humid –adj. when there is a lot of gaseous water in the air

skyrocket –v. to go up or increase at a very fast rate

anticipate –v. to expect something to happen in the future

dose –n. an amount of a medicine needed to give a good result

mild –n. not severe or strong