#106-Amesh Adalja, MD: COVID-19 vs. past pandemics, preparing for the future, & reasons for optimism

KEYPOINTS

• 01

  This is an April 2020 snapshot

  This 40-minute conversation was recorded early in the pandemic. Amesh Adalja, an infectious-disease physician at the Johns Hopkins Center for Health Security since about 2008, works on pandemic prediction, H1N1, Ebola and bioterrorism agents. His estimates reflect what was known then, and some were later revised. Read it as expert reasoning under uncertainty, not as final numbers.

• 02

  He knew early that it couldn't be contained

  When 41 patients in Wuhan were linked to one market, he found it worrying even before human-to-human spread or deaths had been confirmed. Once human-to-human transmission was confirmed, he expected the virus to reach the US, as H1N1 did after it surfaced in Mexico in 2009. He thought it possible the virus was in the US before 31 December 2019, which was controversial. He credits China with publishing the viral sequence very quickly, which let work on diagnostic tests and vaccines start almost immediately.

• 03

  Comparing it with 1957, 1968 and 1918

  The 1957 and 1968 flu pandemics each killed roughly 100,000 Americans. The worst recent flu season, 2017–18, killed about 80,000, and a typical year kills 30,000–60,000. COVID deaths would come on top of flu deaths, not instead of them. A shutdown of society on this scale last happened in 1918, beyond living memory. He also stresses that pandemics hit cities very differently. H1N1 in 2009 infected about 61 million Americans and strained hospitals, but its fatality rate was lower than seasonal flu, so people took it in stride.

• 04

  It will likely become a fifth endemic coronavirus

  Four common coronaviruses cause about 25% of colds. Adalja expected SARS-CoV-2 to join them, with intermediate severity: milder than SARS (about 10% case fatality) but harsher than the other four. Unlike SARS and MERS, it would never go away. He didn't expect full seasonality at first, since so many people were susceptible. Instead he expected successive waves that would ebb and flow as social distancing changed, until a vaccine arrived.

• 05

  His estimate of the fatality rate

  Testing was biased towards severe cases, so the true denominator was unknown. He placed the overall fatality rate at about 0.3–0.66%, citing Imperial College's 0.66% and Germany's roughly 0.37%, and said it could drift either way as antibody surveys arrived. Risk is steeply age-dependent: perhaps around 15% for those over 80, and very low for children.

• 06

  Early models overshot

  February models projecting 200 million US infections and 2–4 million deaths didn't account for undercounted mild cases. Adalja believed cases were undercounted by at least tenfold. Westchester County, which tested heavily after the New Rochelle outbreak, had a hospitalisation rate just under 5%, compared with the 15–20% often assumed. That changes ICU and ventilator planning dramatically.

• 07

  In the US, public health is largely local

  Most public health powers sit with states and localities, not the CDC, NIH or HHS. Rigid early testing criteria, such as travel to China in the previous 14 days, missed spread. New York's virus came mainly from Europe.

• 08

  Testing failures set back the response

  Adalja believes case finding and contact tracing would have been much better with early, broad diagnostic testing. Patients with symptoms overlapping colds and flu went untested. He looked forward to new rapid tests helping to define a 'new normal'.

• 09

  Mass gatherings may drive spread

  Density and prolonged contact at stadiums and similar events make them powerful amplifiers. He expected them to be hard to hold until a vaccine arrived, while acknowledging that lockdown policy might reasonably differ between New York City and less-affected areas.

• 10

  Masks were an early messaging problem

  Early guidance told the public not to wear masks because they wouldn't protect the wearer. N95s were in short supply and uncomfortable to wear for long periods. The guidance was shifting at the time of recording.