Just when you think it's over, it pulls you back in
MICHIGAN STATE UNIVERSITY
THIS GRAPH SHOWS THE FOUR DISTINCT WAVES. WAVE #1 MARCH 1918 (SPRING 1918 WAVE), #2 OCTOBER 1918 (FALL 1918 WAVE), #3 DECEMBER 1918 (WINTER 1918 WAVE) AND #4 FEBRUARY 2020. CREDIT: SIDDARTH CHANDRA
The 1918 influenza pandemic provides a cautionary tale for
what the future may hold for COVID-19, says a Michigan State University
researcher.
After
a decade studying a flu virus that killed approximately 15,000 Michigan
residents, Siddharth Chandra, a professor in MSU's James Madison College, saw
his research come to life as he watched the spread of the COVID-19 pandemic.
"It
was so surreal," said Chandra, who has a courtesy appointment in
epidemiology and biostatistics. "All of a sudden, I was living my
research."
Using influenza infection and mortality data on Michigan from 1918-1920, Chandra identified four distinct waves. The first large peak was in March 1918. "After a second spike in cases in October 1918, the governor instituted a statewide ban on public gatherings," Chandra said. "Much like the restrictions that were put in place during the COVID-19 pandemic."
After
three weeks, the number of cases decreased and the ban was lifted, which led to
another peak in December 1918. "The ban didn't stop the spread of the flu.
It just delayed the spike in cases," he said.
Chandra
mapped the data showing the peaks and spikes in cases from October 1918 and
December 1918 and tracked flu virus case growth by county over time. In
October, counties in the southern part of the state and near the Mackinac
Straits had the highest numbers but by December, the highest numbers of cases
were in the heart of the state.
The
most surprising piece of data came 18 months later in February 1920, when a
statewide explosion of cases created a massive spike even larger than the one
in October 1918. For Chandra, it is an educated guess as to the reasons for
this delayed increase.
"Assuming
it's the same influenza virus, World War I ended in 1918 and the men were
coming home to their families," he said. "We had a mobile agent that
brought the virus home to infect family members, which would explain the
increase in cases among children and the elderly."
Unfortunately,
there is not a way to confirm this, Chandra noted. "We would need samples
from patients in 1920 from across the state. Then, we would need to compare
those with samples from patients in 1918 from across the state, and that's not
likely to happen."
The
weather may have also been a factor since cool temperatures with low humidity
likely provided optimal conditions for the virus to live and spread. Another
factor that played a role was the absence of a vaccine.
"In
1918, there was no hope for a vaccine. In 2021, we have a vaccine
available," he said.
One
of the key insights from the 1918 pandemic that can inform the public health
response to the 2020 COVID-19 pandemic is the number of people who are
susceptible to the virus. Which means that it is possible that a spike like the
February 1920 one will occur in late 2021 or early 2022.
"So
many people will remain susceptible until they get vaccinated," Chandra
said. "Bad things can still happen a year or two from now even if we see a
decrease in the number of cases now. We still have over 200 million people
walking around who are susceptible to the virus, including myself."
Chandra's research is published in the American Journal of Public Health with co-authors Julia Christensen, a graduate of James Madison College; Madhur Chandra, Senior Community Epidemiologist with the Ingham County Health Department and graduate of the Department of Epidemiology and Biostatistics at MSU; and Nigel Paneth, professor of epidemiology and biostatistics and pediatrics at MSU.
Read the study here: https://ajph.aphapublications.org/doi/10.2105/AJPH.2020.305969)