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Types of Viral Infection: How to Protect Yourself From Familiar and Emerging Threats

US News & World Report - Health logo US News & World Report - Health 5 days ago Michael O. Schroeder
a person sitting at a table with a cup of coffee: Sick woman with flu, cold, fever and cough sitting on couch at home. © (Getty Images) Sick woman with flu, cold, fever and cough sitting on couch at home.

Viruses are nothing if not diverse and dynamic – infecting people, animals and even plants. They’re made of genetic material – DNA and RNA – that can only thrive and multiply in living cells. They need us, or more broadly, living “host bodies” to spread. And spread they do, sometimes around the globe.

Certain viruses are familiar to us, even as strains change – like the seasonal flu. Others, like the novel coronavirus (COVID-19) at the heart of the current international outbreak, are new threats. The virus was first identified last year in Wuhan, the capital city of the Chinese province Hubei.

Understanding Viruses

If you look at an electron microscope picture of the coronavirus – i.e., a really magnified, roughly 1 million times, image of the virus – you would see what are called spike proteins sticking out from the surface, notes Lisa Gralinski, an assistant professor of epidemiology at the UNC Gillings School of Global Public Health. The crown-like spikes give the coronavirus its name. Corona is Spanish for crown.

The new coronavirus adds to the known family of viruses that’s linked with the common cold. Two other coronaviruses, SARS (for severe acute respiratory syndrome) and MERS (Middle Eastern respiratory syndrome), have also been the cause of viral outbreaks. Early and more detailed surveillance have allowed experts to more closely study the new coronavirus, compared with when SARS and MERS first emerged. Nevertheless, “there’s still so much that we don’t know,” Gralinski says. Namely, how much of a threat 2019-nCoV may pose worldwide still isn’t completely clear, experts say.

But experts say whether a virus is familiar or exotic doesn’t determine necessarily how much of a danger it poses. For that reason, while emerging threats like corona are taken seriously, it’s important to keep perspective, clinicians advise, and not become complacent about more common viruses like the seasonal flu.

Although it has spread rapidly within China and to other countries, just 13 human cases of the new coronavirus had been confirmed in the U.S., as of Feb. 13. The first death of an American citizen was also reported in February; the 60-year-old died in Wuhan province.

By comparison, millions of people get the seasonal flu and tens of thousands die from it annually. Although the severity varies from year to year, clinicians say the seasonal flu poses a far greater danger in the U.S. than any other virus. “The biggest threat is influenza,” says Dr. Jerry Zuckerman, an infectious disease specialist and vice president of infection prevention and control at Hackensack Meridian Health in Edison, New Jersey.

Protecting Against the Flu – and Other Viruses

It’s difficult to precisely tally the impact of the seasonal flu, as many cases aren’t confirmed or don’t result in a person seeking medical attention. But during the 2018-2019 flu season alone, the Centers for Disease Control and Prevention estimates influenza virus infection caused in the U.S.:

  • 37.4 million to 42.9 million symptomatic illnesses.
  • 17.3 million to 20.1 million medical visits.
  • 531,000 to 647,000 hospitalizations.
  • 36,400 to 61,200 deaths.

For that reason, Dr. Gary LeRoy, president of the American Academy of Family Physicians, strongly encourages people to get a flu vaccine each year. How well a vaccine is matched with a flu strain varies from season to season, increasing or decreasing its effectiveness. But it still protects many from getting the flu, reduces disease severity in those who do get it and decreases overall spread of the virus, experts emphasize.

“That can lessen the probability that you’ll have a serious illness from the virus,” LeRoy says. He adds that it’s important to be aware of who’s most vulnerable. “Children and the elderly, people that have compromised immune systems or respiratory disorders like chronic obstructive pulmonary disease or asthma are really susceptible to these viruses and can become seriously ill or die from those,” LeRoy says.

Experts say it’s important to resistant the urge to overlook the threat posed by this common condition. “Flu is definitely kind of underplayed,” echoes Rachel Graham, an assistant professor of epidemiology at the UNC Gillings School of Global Public Health. “I think people are just so used to it; they equate flu with like a bad cold. But realistically, flu can be very dangerous – especially if you’re talking about very young people or very old people or immune-compromised people.”

With wide vaccine availability, more people should be protected than are, public health experts say. But because many don’t get the vaccine, “and also because people tend to go to work with symptoms, they tend to go out to the grocery store with symptoms, things spread,” Graham says.

Besides vaccination for the flu, hand-washing is strongly encouraged to protect against the spread many different infectious diseases, including coronavirus and rhinovirus, the virus responsible for most common colds.

What’s become clear with the new coronavirus is that the risk of transmission is highest when people are sick, and that it’s transmitted person to person mainly via respiratory droplets: so coughing, sneezing, wiping a runny nose and touching another person. Just as with the flu, hand-washing is an important way for individuals can decrease their risk of getting coronavirus, says Dr. Albert Ko, chair of the department of epidemiology of microbial diseases at the Yale School of Public Health.

In fact, hand-washing thoroughly with soap and water is perhaps the single-most important safeguard against getting viral infections, clinicians say. In addition, stay home when you’re sick with any infectious disease.

Comparing Viral Threats

It can be difficult to gauge the danger from an emerging threat, like the coronavirus. But the initial estimate by the World Health Organization is that about 2% of people who contracted the new coronavirus died from it.

Whether this case fatality rate will change as more cases are detected isn’t clear. But already more people have died from coronavirus than SARS. And coronavirus is continuing to expand its reach. “We can delay perhaps the spread, but it’s not clear whether we can actually prevent the spread,” Ko says.

Here’s how the tolls compare for several coronavirus outbreaks, according to WHO:

  • 2019-nCoV: the latest coronavirus threat: As of Feb. 13, around 60,000 cases had been reported, most in China, with over 400 cases confirmed in 24 other countries and more than 1,300 deaths worldwide.
  • SARS (SARS-CoV): 8,098 cases in 26 countries, with 774 deaths. There haven’t been any known cases of SARS reported since 2004.
  • MERS (MERS-CoV): New cases still being reported; 2,499 lab-confirmed cases in 27 countries since April 2012 through December 2019; 861 deaths.

There have only been two confirmed cases of MERS in the U.S., according to the CDC. Both were health care workers who’d lived and worked in Saudi Arabia, where the disease was first reported. Both individuals were hospitalized in the U.S. and fully recovered.

In total, 75 probable cases of SARS and no deaths were reported in the U.S.

By comparison, the swine flu, or H1N1, pandemic that spread across the country and globe in 2009 and 2010 led to an estimated 60.8 million cases, 274,304 hospitalizations and 12,469 deaths in the U.S. alone, according to the CDC. Originating in pigs, the virus spread rapidly from person to person. Globally, the vast majority of deaths occurred in people under 65. That differs from the typical seasonal flu, for which most deaths involve older adults.

The H1N1 flu virus still circulates today with the seasonal flu, but it doesn't sicken as many people as it did when it first emerged. It's also covered by the flu vaccine – yet another reason to get the vaccine.

Viral threats vary considerably just as the microscopic organisms themselves do. Three that illustrate the wide range and variability in how they’re spread are:

HIV continues to be an epidemic – and a top viral threat, Zuckerman notes. Spread by coming in contact with body fluids, most commonly through unprotected sex or sharing needles, this virus attacks the body’s immune system.

Improvements in treatment have also helped reduce spread of HIV, where more than 1 million people have the virus – including 1 in 7 who don’t know it – according to federal data. More than 16,000 died from the disease in 2017, the latest government numbers.

While a concerted effort has been made to reduce the spread of HIV, another viral threat, measles, is reemerging due to declining vaccination rates in some places. “We’ve seen a large resurgence of measles in the U.S.,” Zuckerman says.

In total, 1,282 individual cases of measles were confirmed in 31 states from Jan. 1 to Dec. 31, 2019, according to the CDC. That resulted in well over 100 hospitalizations and reported complications including pneumonia and inflammation of the brain called encephalitis.

That’s the most cases reported in the U.S. since 1992, according to the agency. The CDC notes that close to three-quarters of the cases were linked to recent measles outbreaks in New York, and that most of the cases involved people who weren’t vaccinated against measles.

Another viral threat that we now deal with annually is West Nile Virus, which first appeared in the U.S. in 1999. This is spread by infected mosquitoes, and can cause symptoms such as a fever, headache, skin rash and vomiting. Less than 1% will develop a serious neurological condition like encephalitis.

According to the CDC, in 2019, there were 917 total confirmed and probable cases of West Nile, leading to 51 deaths. It’s one more reminder that when it comes to protecting yourself and your family against viral threats, the approach – like the viruses themselves – must be dynamic.

“For things that are mosquito-borne, like we see during the summer, then the protection is using mosquito repellants, using clothing that covers the skin,” Zuckerman says. “So it depends on the season and the virus as to what are some the protective steps that you can take.”

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