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COVID vs. Flu - Getting Closer?

Volume 6, Issue 8 | October 5, 2022 Mara G. Aspinall and Liz Ruark Oct 5

ALSO IN THIS ISSUE California schools required to publish COVID testing plans Another pandemic will come. How will we prepare? COVID in big hairy armadillos (yes, that’s their real name) New and Noteworthy California schools required to publish COVID testing plans - with user-friendly reporting Per legislation that California’s governor signed last week, all school districts in the state are now required to have a COVID testing plan that follows state department of public health guidelines. They also have to publish their plan online. These plans don’t have to include on-site testing, but the districts do have to make sure that their testing data is in a format that makes it easy for families and districts to report results. Of note: The department of public health also has to expand its guidance to include pre-K and childcare centers. Commentary: This is great news, and we’d love to see other states following suit. But there are caveats. 1) Given the lack of integration in public health data across the country, it would be great if California schools could pick one best-in-class test-reporting technology, which then could become the industry standard across the nation. If we want good national public health data, we need to be able to compare apples to apples. 2) The state isn’t required to approve these plans, so districts are on the honor system to make sure what they publish actually follows the guidelines. And, of course - 3) Plans are only good if they get used when they need to be. If the schools are to implement testing when needed, they’ll need support from the state - which can’t happen until the legislature approves funding. Food for Thought It’s still not “just like the flu” - but it’s getting a lot closer Over the course of the pandemic we heard a lot of questions about how COVID is or is not “just like the flu.” As the 2022 /23 flu season gets underway, we share our analysis for the US. Baseline: Over the last two and a half years of the pandemic, COVID has been much worse than influenza. Today, however, there’s great news: COVID’s short-term health impact, with some exceptions, is now equivalent to the flu. Ground Rules: We compare COVID to the last two flu seasons combined. We use only reported numbers from the CDC. We know that there is undercounting on both diseases, but we don’t want to make assumptions on either in this analysis. We also assume that all deaths occur in hospitals. Case Numbers: Reported COVID cases now total 96 million. The number of reported cases from the last two pre-COVID flu seasons combined was 91 million. Deaths: COVID deaths have now reached almost 1.1 million people. Flu deaths for two seasons combined are 95,000. Mortality Rate: Overall, since the beginning of the pandemic, 1.1% of the people who have contracted COVID have died. When you say it that way - that 99% recover - maybe it does not sound too scary. But compare that to flu, which has a 0.1% death rate. COVID has eleven times the influenza mortality rate of flu overall. But during the Omicron BA.5 era, mortality rate for COVID has declined. During the time that that variant has been dominant, COVID’s mortality rate has been essentially equivalent to the flu - about 0.1%. That’s the best news yet. The mortality rate of hospitalized COVID patients, which is now solidly in influenza territory, provides strong evidence for this statement. A confounding factor is that, in the last year, as many as half of “hospitalized COVID patients” have been patients who were admitted for other reasons and were incidentally found to have COVID. However, given that this is more true of COVID than influenza, that only strengthens the case that the current burden of COVID approximates that of flu.


Looking into the future, there are still three important points of differentiation between the two viruses.

  1. COVID’s superpower has been its ability to spread before those infected realize they are ill, both from presymptomatic patients (during the two to three days before symptoms appear) and from completely asymptomatic cases (variously estimated as 10-40% of cases). Influenza can’t do that. Symptom onset is a consequence of our innate immune system swinging into action. In 2020 we were nearly all immune-naive, so viral infection was in full swing long before our inflammatory systems woke up to mount a response. There is some (anecdotal) evidence that the pre-symptomatic transmissible period is declining under Omicron, at least partly because the majority of us are no longer immune-naive, thanks to natural infection and/or vaccination.

  2. SARS-CoV-2 has mutated further and faster than influenza. There are several factors driving this, but the major one is that this virus has only just moved into humans, allowing rapid exploration of available mutation space. Then there’s the sheer scale of the pandemic, giving the virus billions of shots on goal to find advantageous mutations. By contrast, influenza has been in humans for thousands of years, and its current mutation profile reflects that: gradual evolution in humans with occasional major breakouts due to new jumps from animal reservoirs (especially birds and swine).

  3. Long COVID appears to be far more prevalent than the aftereffects of influenza (10-33% of COVID cases vs. few if any from flu). However, this may be yet another case of not finding things because we’re not looking for them. We do not yet know much about the landscape and drivers of post-acute infection syndrome, and it may be higher for flu than has previously been realized.

Our hope now is that we can manage COVID as effectively as we have been able to for seasonal influenza. This requires ongoing surveillance, regular testing, and masking to protect the vulnerable. We cannot let our guard down as we have in the past. We need to prepare for the next pandemic - but how? As The Atlantic’s Ed Yong described in “We created the ‘Pandemicene’,” the 21st-century world has an ever-increasing potential to produce zoonotic infections that could bring the world to a halt. Climate change and habitat erosion have pushed more species (including humans) into closer contact with each other - one model presented in Nature offers predictions as to where this will happen as the world warms. Human transport networks allow infections that spill into our species to swiftly spread worldwide. (If you want a real-world example that will keep you up at night, read up on primate hemorrhagic fever-causing arteriviruses in Cell (October 2022). These are a real and present threat, since they readily infect humans, and we have no immunity to them.) But evidence from the past shows that we as a nation are hopeless at pandemic preparedness. We’re only willing to pay significant attention to infectious disease when we ourselves are in the midst of a crisis, and the moment that crisis subsides, we believe it’s over and won’t come back. We don’t like to pay attention to warnings that happen in other parts of the world, either. SARS-CoV (2002/2003) was a close call that was largely ignored in the West. MERS, with its Ebola-like 50% mortality rate, was discounted because it was mostly transmitted by infected camels. Commentary: So what now? Going back to our touchstone, Ed Yong, unless something changes, “The pandemic’s legacy is already clear - all of this will happen again,” because our nation refuses to repair what’s broken. As Yong sees it, that includes not just its chronically underfunded public health system, but prisons, nursing homes, for-profit health care, its “convoluted supply chains and just-in-time economy,” its frayed social safety nets, and last but perhaps most important, its deeply entrenched racism, with the disproportionate health burdens that entails. Clearly, preparedness is the only option, but what exactly will that look like? High-cost but relatively rare events are very hard to evaluate. We know our natural intuition about probabilistic events is deeply flawed (see any behavioral economics text, e.g., Daniel Kahneman’s “Thinking, fast and slow”). Governments want (need?) to breathe a sigh of relief and move on to other issues, but we must have a plan in which the costs are carefully weighed against the benefits - it is just not possible to be fully prepared for anything or everything that might happen. That being said, we can’t forget that the cost of being unprepared for COVID-19 was immense. We do not yet have a full accounting of the cost of shutting down the global economy for two years, but we urgently need a consensus on what we must do (and not do) for the future. Quick Hits A preprint published at the end of August described a March outbreak of the Gamma variant of SARS-CoV-2 in big hairy armadillos three months after that variant was no longer detectable in humans in the region. The animals were being bred at the University of La Pampa, in Argentina, for use in neuroscience research, when they developed COVID symptoms. (What does an armadillo sneeze even look like?)

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