The influenza virus is a quick-change artist.
Most viruses mutate quickly, but “flu is a master at mutating,” said Ruth Blackmon, senior director in quality resources management at Bassett Medical Center in Cooperstown and an expert in disease control. “And it mutates in small ways, in general, from season to season.”
Five to 20 percent of the U.S. population gets the flu each year, and more than 200,000 people are hospitalized as a result of flu-related complications, according to the federal Centers for Disease Control and Prevention in Atlanta.
“There have been a lot cases reported of flu from Herkimer and up in that direction,” Blackman said. “We’ve had very few reported in Otsego County so far.”
The vaccine changes from year to year because those small mutations in the genetic makeup of each virus strain usually render the previous year’s vaccine impotent.
This year, the flu strains infecting people are a good match for the vaccine that healthcare providers began administering in September, according to a report released last week by the CDC.
That’s the way it works most of the time.
“But once in a while we see a massive shift” in the virus’s genetic makeup, Blackman said.
When that happens, millions, even tens of millions, die. The Spanish flu pandemic of 1918 killed 20 million to 50 million people from January 1918 to December 1920. It is among the worst natural disasters in human history.
For most people, influenza symptoms such as coughing, sneezing, runny nose, fever and sometimes gastrointestinal distress cause a few miserable days, but little danger. Other people are not only at greater risk of contracting the disease, but they are more likely to suffer serious consequences.
“Younger children and older adults tend to be more susceptible; pregnant women,” too, Blackman said last week.
“It’s a similar reason for all three in that it’s the state of your immune system to a certain extent.”
Those people also at higher risk for complications, such as pneumonia, the CDC says. Thus, a flu vaccine doesn’t just protect a recipient; it protects people to whom the recipient may otherwise pass the virus — people who often have a lot more to lose.
How it spreads
“The flu spreads through droplets that people cough or sneeze out,” Blackman said. “Those can land on surfaces and be picked up by hands and then transmitted to eyes, nose, mouth. If you touch some other area on your skin, you’re not going to get the flu.
“But if you touch your eyes or your nose, especially, it can be transmitted that way — or if someone sneezes or coughs and doesn’t cover their mouth and you are within 3 to 6 feet of them, the droplets can actually travel that far.”
This, it’s important for flu victims to cover their mouths when they cough or sneeze, Blackman said.
She said that studies have shown that the virus can survive on a hard surface as long as 48 hours and on paper or cloth as long as 12 hours. That’s why public-health workers recommend frequent hand washing as one way to improve the odds of avoiding the flu.
Once infected, a victim’s symptoms show up in one to four days, according to the CDC, and most healthy adults may be able to infect others a day before the onset of symptoms. They remain contagious for five to seven days after becoming sick, the agency says.
You cannot get the flu from a flu vaccine, Blackman said. The most commonly administered form — injectable vaccine — doesn’t even contain the virus, she said.
Instead, it contains pieces of the virus’s code that fool the immune system into producing antibodies for an infection that doesn’t exist. A week to 10 days later, the immune system is fully armed to do battle with a real flu virus.
“The usual reaction that people have is soreness in your arm,” Blackman said. In rare cases, according to the CDC, patients develop mild fever or headache.
A newer vaccine, intranasal — a nose spray — does contain live virus, she said. But you can’t get the flu from that vaccine either. Why? Because the virus has been altered to die at body temperature. It lives long enough to provoke an immune response, but it quickly dies once it’s in the body, Blackman said.
In exceptionally rare cases, the injectable vaccine can produce a very dangerous condition called anaphylactic shock, usually because a patient is allergic to chicken eggs, which are used in making the vaccine.
Most of those people have never received the vaccine before, Blackman said.
Building a vaccine
The flu season in the Northern Hemisphere runs from September to the end of March or sometimes into early April, depending on its progress, Blackman said. It’s the opposite in the Southern Hemisphere.
“Lots of people think that they get the flu because they got cold outside, but that’s generally not the case,” Blackman said. In fact, cold kills the virus. But cold weather forces people indoors, “and so it spreads more,” Blackman said.
A unit of the CDC decides which strains to focus on during the spring preceding the next season in September.
“They take a look at the pattern of the previous season right through the whole season and look for any new or different viruses that have been detected, different flu viruses, different strains,” Blackman said.
But it’s still hard to predict which forms of the virus will be spreading six months in the future. International travel complicates the process, allowing strains of virus to jump thousands of miles in hours.
“Those patterns really affect the flu season in some ways,” Blackman said. “We’ve wondered sometimes if we might not just end up with a 12-month-a-year flu issue. ... People travel all the time.”
The CDC’s conclusions about the coming season are provided to vaccine manufacturers. If the CDC predicts correctly, the vaccine matches the prevalent viruses. This year, it does, according to the latest CDC report.