Viral Disease and Pregnancy: Why COVID-19 is Worse than Seasonal Flu

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A half truth makes a great lie. Attributed both to Benjamin Franklin and, in a slightly different form, to a Yiddish proverb, this saying shines a spotlight on a misconstrued notion that has been cited as part of an attempt to downplay the danger of the COVID-19 pandemic. Essentially, the idea is that is that seasonal influenza –the flu– kills tens of thousands of people each year in the United States alone. When stated by people in positions of leadership over the past few months, the implication has been that health authorities have over-reacted to COVID-19. Now, if you look up influenza on the website of the US Centers for Disease Control and Prevention, you’ll find that, indeed, epidemiologists have calculated that the flu killed from 24,000 to 62,000 Americans between October 1, 2019 and April 4, 2020. Furthermore, if you look up coronavirus deaths on Worldometer or the Johns Hopkins Coronavirus Resource Center, as of April 14 (when I am writing this), you’ll find that the number of COVID-19 deaths has just passed 25,000, and so is getting into the range of influenza, but is not dwarfing it by any means. In place of the numbers of deaths, you can also make similar comparisons with the numbers of cases of the two classes of disease, and you can also hone in on the numbers in pregnant women in whom flu can take a harsher course compared with women of similar ages who are not pregnant. But factors that make a huge difference in the toll that a disease takes include how contagious a disease and the timing of the disease’s spread. With these things in mind, we need to unpack the story about the flu in comparison to COVID-19.

Let’s begin with a caveat that influenza is a family of viruses that potentially can be just as bad, or worse, than SARS-CoV2, the virus that causes COVID-19. The most dramatic example is the notorious 1918 flu pandemic, which struck an estimated 500 million people (one third of the humanity of that time period) and killed from 50 million to 100 million people. That pandemic differed from seasonal flu in a couple of major ways. First, the 1918 flu was more contagious and more deadly than the seasonal flu. Second, the 1918 flu was most deadly in young to middle age adults, a population that included pregnant women, whereas seasonal flu is most dangerous in people who are old and those who are weakened because they suffer from other medical conditions. In terms of who is at risk, this makes COVID-19 more like seasonal flu than like the 1918 flu, but with seasonal flu there is a way to lower your risk: get a flu shot, the influenza vaccine.

Pediatricians and other physicians have generally done an excellent job convincing patients and parents of the importance of being vaccinated against classic, highly contagious diseases, such as measles, rubella, mumps, pertussis, and polio, but it has been more challenging to get people to get their flu shots every year. This is partly related to the fact that you need a yearly shot, a fact that reminds people that flu vaccines are not nearly as effective as the vaccines against measles and polio. Additionally, the effectiveness of flu shots varies from season to season.

The reason for the effectiveness being variable and less than what we want from a vaccine is that influenza viruses easily undergo mutations of the genes that carry instructions for making proteins that sit on their surfaces. Vaccines teach your immune system to make antibodies that attach to such proteins, and in doing so neutralize the virus. Each flu season, there are several different versions of influenza virus circulating and vaccine researchers must predict which flu viruses will dominate and create a vaccine that will work against them. While getting such a seasonal flu vaccine will not guarantee that you won’t come down with the flu, it actually does reduce your risk of catching the most serious flu viruses of the season, plus the flu shot tends to reduce the duration and severity of your disease, if you do catch the flu. Whether you are pregnant or not, by getting a flu shot, you are less likely to need hospitalization, less likely to require admission to the intensive care unit (ICU) if you do get hospitalized, and less likely to die from the flu.

Thus, one thing that makes flu “better” than COVID-19 is that, for the time being, there is vaccine that you can get against the flu. Scientists are working on a universal flu that vaccine that would work better and not need to be updated every year, but for now the seasonal vaccines, though not perfect, are all that we have. If there were a vaccine against COVID-19 that could reduce your chances of getting infected in the first place and also of getting severely ill if you do get infected would you not welcome that vaccine? The same reasoning should apply to getting your flu shot.

The other phenomenon that we must discuss is timing. Projections for COVID-19 place the death toll at approximately 60,000 at minimum before the current US outbreak ends to as many as 100,000 or even 200,000. In other words, the best-case scenario is that COVID-19 deaths will equal the high end of the flu death projection of 24,000 to 62,000 for the bulk of the current season (October 1 to April 4). Importantly however, the 24,000 -62,000 deaths are spread out over many months. Comparatively, even considering only the 25,000 Americans who have already died from COVID-19, most of those deaths have occurred in the past few weeks and the number of new infections continues to rise, especially in hot spots, such as New York and New Jersey. Consequently, health facilities are overwhelmed, which is why various temporary treatment centers have been set up. Hospital beds that would otherwise be for flu patients, for heart attack patients, and for patients with bacterial pneumonia are needed for COVID-19 patients. The fact that COVID-19 is dangerous for health care workers adds to the problem, because the needed precautions –the donning and doffing of personal protective equipment takes up a lot of time and requires additional personnel.

Given all of this, it’s not a good time to have to go to the hospital. When it comes to the delivery room, many precautions are in place. Depending on your location, your partner may or may not be allowed to join you for the birth, but one way or another measures are being taken to protect you and your baby against COVID-19. In contrast, while there are also efforts to keep flu patients who are negative for COVID-19 separate from COVID-19 patients, flu uses the same types of hospital facilities as COVID-19 uses. It depends on internal medicine wards, and, for those who become very ill, it depends on ICUs. Additionally, if you arrive at the emergency department of a hospital with flu symptoms, you will look like a COVID-19 patient until you are tested for both COVID-19 and the flu and come out to be negative for COVID-19.

While a lot still needs to be learned about the interaction between pregnancy and COVID-19, what is very clear is that the interaction between the flu and COVID-19 is not good. Patients who suffer from both flu and COVID-19 simultaneously tend to suffer more serious disease, more complications, and are more likely to die compared with patients with COVID-19 without the flu. Consequently, you should take all available precautions against getting the flu. Some of these precautions are the same precautions that you take against COVID-19, namely social distancing (we stay away from one another, go out for only essentials, such as grocery shopping, and wear masks and gloves when doing that shopping. But another precaution is not the same, and that’s getting vaccinated, since there is a flu vaccine but not yet a COVID-19 vaccine.

This brings us to the answer to the question posed as the title of this post, namely why COVID-19 is worse than flu. Part of the answer is that the seasonal flu is less contagious and also less likely to produce life-threatening complications, like the kind that put people on ventilators. But the rest of the answer is that, right now, there is more that we can do to prevent the flu. You can get your flu shot, so make sure that you do that, even now when it’s late in the season. Then, continue to get your shot each year until there is both a COVID-19 vaccine as well as a universal flu vaccine.

David Warmflash
Dr. David Warmflash is a science communicator and physician with a research background in astrobiology and space medicine. He has completed research fellowships at NASA Johnson Space Center, the University of Pennsylvania, and Brandeis University. Since 2002, he has been collaborating with The Planetary Society on experiments helping us to understand the effects of deep space radiation on life forms, and since 2011 has worked nearly full time in medical writing and science journalism. His focus area includes the emergence of new biotechnologies and their impact on biomedicine, public health, and society.

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