Where Is the Flu?

flu this year

It’s a serious question. Every year millions of Americans are urged to vaccinate against influenza (aka the flu), and while this disease is not quite the threat that COVID-19 has become, it exacts a significant toll each year, raging most wildly from December to February. The CDC estimates that influenza results in 45 million illnesses, 810,000 hospitalizations and up to 61,000 deaths each year in the country. But not this year, baruch Hashem.

Make That 925 Cases So Far

One illness is too many. But, b’chasdei Hashem, this number is a far cry from 45 million.

The difference is staggering. Sure, COVID is gobbling up the headlines, but the flu hasn’t merely taken a back seat. Baruch Hashem, it’s literally barely there at all.

Globally, the WHO estimates a billion people are infected with flu each year, with nearly 5 million developing severe cases and a death toll of somewhere between 290,000 and 650,000. But this year all of that has changed.

Although the flu season runs deep into the winter and through the spring, and although it is possible the cases could pick up, chas v’shalom, despite the warming weather, and although it is also possible that Influenza B, which tends to circulate later in the season, may still make its mark, with all of those caveats the world’s still looking in pretty good shape, kein ayin hara, when it comes to beating back this old foe.

Data from the Southern Hemisphere, which has already passed through its winter and is currently enjoying its summer, is promising.

After the flu season of 2019-2020 ended early in the North, the South began its sojourn into winter, with Australia, Chile and South Africa identifying a grand total of 51 cases of flu out of 83,000 swabs.

And now, as the North makes its way through the dreary winter months, all seems silent on the flu front as well. In Japan there was a total of 1,000 flu cases compared to 800,000 the year before. In England, which generally sees a few thousand people in the ICU with the flu each January, zero ICU cases were reported last month.

This is especially welcome news for frontline workers and hospitals where resources are being allocated for pandemic management.

So what, exactly, is going on with the flu?

Everything Somehow Comes Back to COVID

Dr. John Loike, biology professor and bioethicist at Touro College and Interim Director of the Biomedical Ethics & Humanities Program at Touro’s New York Medical College, told Hamodia that one of the obvious explanations for a blessedly quiet flu season is the COVID-19 restrictions. Our collaborative efforts to distance and mask have been effective.

The world once considered it unavoidable that hundreds of thousands of people would die each year of the flu, but now experts are asking if our new learned behaviors may be valuable to contain future illnesses or the return of heavier flu seasons.

“Like the COVID virus, the flu virus is transmitted primarily via the air,” Dr. Loike says. “This is especially true for children who are considered as a ‘great contagious engine’ for the flu.”

While children were originally assumed to be superspreaders of COVID-19 before more data became available indicating the opposite, when it comes to other viruses — like influenza — they definitely do an excellent job of spreading their germs far and wide. Children have long been identified as vectors of travel for viruses like the flu, carrying it around to family and friends.

Dr. Niket Sonpal, professor at Touro College of Osteopathic Medicine, said in an interview with Hamodia that 2020’s new behaviors have had a drastic impact on flu transmission. “Flu is a highly infectious disease and causes morbidity and mortality every year,” he says. “This year, however, the rates are lower … entirely due to the measures in place for COVID-19. So many people are staying home; schools are closed; hand-washing, masks, and social distancing have all reduced exposure and transmission.”

While some have posited that flu cases are likely more widespread but simply aren’t being detected because they are being mistaken for COVID-19, Dr. Sonpal rejects that line of thinking. “The cases do have similar presentations, but testing for flu is available as well and is a rapid test to help differentiate.”

Although COVID-19 is a compelling explanation for flu reduction, it doesn’t seem to tell the whole story. Even in countries where fewer restrictions have been put in place and lockdown measures only loosely observed, flu rates have similarly dropped, so other factors may be at work.

The Vaccination Campaign

“The flu vaccine was pushed with more gusto and also is playing a role in keeping the rates low,” says Dr. Sonpal.

Dr. Loike similarly notes that a dramatically higher number of Americans have received the flu shot this year, a trend which seems to have helped some Southern Hemisphere countries as well. For example, Australia jabbed 7.3 million citizens for its winter season in 2020 compared to just 4.5 million in 2019. In England, around 80% of elderly people received a flu shot this season, which is 10% higher than last year. In the U.S., vaccination rates have been trending upward over the decade, with over half the population receiving the vaccine in the winter of 2019-2020. This year’s vaccination effort is not yet completed, but it appears the numbers will be even higher than that. As of November 2020, 188 million doses had been shipped out across the U.S. compared to 169 million the year before.

Some doctors are so convinced the higher vaccination rates have really stalled the flu that one virologist out of Tokyo suggested requiring future air travelers to show they were vaccinated against the flu as well as COVID-19 before allowing them entry. While this might have sounded outrageous to many just a year ago, for 2021, it seems almost probable.

COVID Trumps All — Again

“A third reason for the low incidence of flu is that there may be competition between the COVID virus and the flu virus from attacking the lung cells,” says Dr. Loike. “It appears that the COVID virus is a better attacker for the lungs than the flu virus and prevents the flu virus from attacking those cells.”

One hypothesis out there is that SARS-CoV-2, the virus that causes COVID-19, may be increasing people’s immunity against other viruses. One study put out this past spring found that people testing positive for COVID-19 were less likely to be carrying other common viruses. Still, the research into this theory is in its infancy.

“A fourth possible reason is that there is a principle in immunology called ‘cross-over’ immunization,” says Dr. Loike. “When you contract a virus like the one that causes COVID, your immune system can potentially generate an immune response that will also help protect you against other viruses, like the flu. What is really important in analyzing flu and COVID outbreaks is that as we collect data from the CDC we will gain a better understanding on the critical behavioral and therapeutic actions, such as vaccines, [that] people take to protect themselves against respiratory viruses as well as the repercussions of these actions for future viral outbreaks.”

Travel

While many may be mourning their vacations, lack of travel might well illuminate why flu is so sparse. Influenza typically makes its way around the globe each year, maintaining a low-key but year-round presence in the tropics. The profit nosedive that airline companies have suffered over the past many months highlights just how little international travel is being undertaken. Presumably, the flight of flu is also affected.

That having been said, no one really understands why flu moves around. Weirdly, Australia can have high rates of flu for a few years while its neighboring country, New Zealand, can have low ones.

Flu of the Future

Regardless of the reason, it’s a welcome relief to get a flu vacation. Some are hopeful that this trend may stick around.

“The decrease in the cases of flu this season may affect future flu epidemics because there is less virus around to mutate into the next season,” says Dr. Loike with an optimistic tone. Less mutation may mean fewer new strains to go around.

Conversely, other experts have argued that the lack of flu may just cause a serious uptick in years to come. A Johns Hopkins researcher believes the lack of exposure this year may mean less immunity down the road.

Another consequence of a quiet flu season may make predicting and designing next year’s flu vaccine more difficult. Since researchers rely on the study of strains from the Southern Hemisphere to predict what will infect the rest of the world in the coming months, this year the Southern Hemisphere hasn’t been very accommodating.

A possible positive outcome is that the less dominant strains of flu may die out. Permanently. Which would make the flu picture a whole lot simpler. And because every optimist comes along with a pessimist, other experts warn that the lack of viral competition in human hosts may just pave the way for new swine-flu variants. One of the things holding back those variants is the natural immunity people build because of circulating flu.

The prediction market is always robust with colorful doomsayers and utopians, but for now, we can all just appreciate the very welcome respite from influenza. When it comes to the virus circus all around us, in the year 2021, having a little less circus to go around is a breather for which we can all be grateful.

An RSV Reprieve

Interestingly, flu isn’t the only virus on the decline this year. There are hundreds of infections which cause respiratory symptoms and some of them have also been going underground. Again, data from the Southern Hemisphere which has completed its winter season is helpful in following the trends.

One of the viruses to take a dip is respiratory syncytial virus (RSV), a common virus that typically infects young children and which can occasionally lead to pneumonia. It generally causes about 5% of deaths globally in children under age 5.

In Australia, RSV in children declined by 98% this year, despite schools remaining open.

The RSV halt may, unfortunately, be short-lived. One region in Australia has already reported an increase in this infection, with some experts predicting a bigger wave ahead.

Influenza Fact Sheet

Influenza A and B are responsible for the yearly flu. Within both categories are a number of subcategories and strains.

The flu viruses are always changing. They can do this in one of two ways. A) Antigenic drift is when small mutations occur. B) Antigenic shift is when a major mutation occurs.

Influenza A is found in many different animals, including ducks, chickens, pigs, whales, horses, seals and cats. Influenza B is found only in humans. While it is unusual for humans to pick up flu from animals, there are some cases of this occurring.

Cough, sore throat, runny or stuffy nose, muscle or body aches, headaches and fatigue are the most common symptoms of the flu.

Children are most likely to get sick from flu while older people are least likely. Median incidence values (or attack rate) by age group were 9.3% for children 0-17 years, 8.8% for adults 18-64 years, and 3.9% for adults 65 years and older.

You’re most contagious on days 3 and 4 of your illness.

Those most at risk of developing flu complications are: young children, especially those under six months; adults over 65; residents of nursing homes; expectant women; those who are immunocompromised, people with chronic illnesses such as asthma, heart disease and diabetes; and those who are severely overweight with a BMI of 40+.

The Common Cold Is Sticking Around

Rhinoviruses, one of the major causes of the common cold, especially in kids, haven’t been as kind. With over 100 strains of this virus in existence, generally a dozen or so circulate in any given community.

One study out of the U.K. revealed a lower rhinovirus rate during the summer but a quick increase once school started in September. (It is possible that detection of rhinovirus is higher because people are testing more in general now.)

No one is quite sure why other viruses have backed off while the common cold is still going strong. Unlike the flu and coronaviruses, rhinoviruses do not have an outer lipid coat which is vulnerable to soap, making it more difficult to kill. It’s possible rhinoviruses are also more likely to cling to surfaces and stick around, making transmission via toys, desks and door handles more likely.

In better news, one study of 800,000 participants found that adults who had sustained a cold sometime during the year were less likely to test positive for COVID-19. And, like most things relating to COVD-19, no one knows why that is, but if the cold is helping in the fight against the global pandemic, then maybe no one is complaining about those annoying runny noses.