Data: WHO, NEJM and CDC; Chart: Naema Ahmed/Axios

The COVID-19 pandemic is caused by a virus humans haven't encountered before — meaning our bodies have no built-in immunity to it and researchers are frantically working to learn more about it.

Why it matters: While there are important lessons to be learned from other pandemic flus and even seasonal flu outbreaks, the coronavirus pandemic is new and not exactly comparable, making predictions, policies and treatments all the more difficult.

The latest: The coronavirus is spreading throughout the U.S., with at least 35,224 confirmed cases and 471 deaths early Monday morning, per Johns Hopkins' Center for Systems Science and Engineering.

  • Meanwhile, the Centers for Disease Control and Prevention estimates the 2019-2020 seasonal flu has caused at least 38 million illnesses, 390,000 hospitalizations and 23,000 deaths so far this season.

What they're saying: Anthony Fauci, who's served as director of the National Institute of Allergy and Infectious Diseases since 1984, told a JAMA podcast he's worked on multiple infectious disease crises "but nothing of the magnitude of this."

  • One of the problems, he said, is that without strong containment and mitigation efforts, it hits society and its health care system "all of a sudden — boom! It starts to skyrocket."
  • The World Health Organization on Friday warned against dismissing the coronavirus as just a bad outbreak of the flu, saying overwhelmed health systems are "collapsing" around the world.
  • “This is not normal. This isn’t just a bad flu season," WHO's Mike Ryan said.

While both seasonal flu and COVID-19 cause similar respiratory illnesses, there are key differences between the viruses.

  • Influenza has an incubation period of roughly 2-3 days, whereas the coronavirus incubates longer (5-6 days on average) before symptoms appear, possibly allowing more people to unknowingly spread the virus.
  • On average, 1.3 people catch the flu from an infected person versus 2-3 for the coronavirus.
  • There's a flu vaccine and multiple effective treatments, so many exposed to the flu will have lessened symptoms. There's no vaccine or treatment yet approved for COVID-19.
  • Children appear to be more susceptible to severe complications from this seasonal flu than from COVID-19, with the CDC reporting the highest number of influenza-associated deaths (149) at this point in the season, with the exception of the 2009 flu pandemic.
  • But, the overall mortality rate for COVID-19 is between 10 and 40 times higher than the average 0.1% mortality rate for the seasonal flu.

The U.S. can learn from both Asia and Europe, which experienced cases of COVID-19 earlier than the U.S., Julie Fischer of Georgetown University's Center for Global Health Science and Security tells Axios.

  • China is providing data showing what measures are working better than others, and is conducting treatment tests on patients, which will be valuable, she said.
  • In South Korea, robust diagnostic testing using creative measures like drive-thrus combined with strong health care followup shows the importance of isolating the right people early enough to limit the spread, Fischer says.
  • Italy tried to do a widespread but unfocused social distancing. There's been some success in stemming the outbreak in certain areas that tested a large number of people, tracing and quarantining those who have been in contact with positive cases. But, it wasn't early enough or sufficiently extensive, and many parts of Italy are now overwhelmed.

Longer term lessons can be drawn from prior pandemics, like the Spanish flu of 1918, Fischer says.

  • Comparing Philadelphia's response with that of St. Louis is quite striking, Fischer says. Philadelphia decided to hold a 200,000-person parade to boost morale — but this led to widespread infections. In contrast, St. Louis rapidly battened down the hatches and reported a smaller epidemic.
  • Another lesson from the Spanish flu was that closing schools early on was "one of the most beneficial" non-pharmaceutical interventions.

The bottom line: "This is not an 'abandon all hope, ye who enter here,' scenario," Fischer says. "We can focus our strategy and become much more aggressive" in diagnostics testing and social distancing measures until scientists make advancements on vaccines and treatments.

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Coronavirus dashboard

Illustration: Eniola Odetunde/Axios

  1. Global: Total confirmed cases as of 7:30 p.m. ET: 11,565,541 — Total deaths: 536,658 — Total recoveries — 6,258,697Map.
  2. U.S.: Total confirmed cases as of 7:30 p.m. ET: 2,922,000 — Total deaths: 130,208 — Total recoveries: 924,148 — Total tested: 36,032,329Map.
  3. Public health: Case growth outpacing testing in hotspots.
  4. States: West Virginia becomes latest state to mandate facial coverings in public.
  5. Politics: Atlanta Mayor Keisha Lance Bottoms tests positiveCuomo accuses Trump of "enabling" the coronavirus surge — Sen. Chuck Grassley opts out of attending GOP convention over coronavirus concerns.