After the disease reached Pennsylvania, researchers and field workers acted to slow its spread.
Their plan relied on testing, mapping and quarantines, but they faced challenges.
Individuals could transmit the disease before showing symptoms.
There was no vaccine or treatment.
And infected deer refused to stay 6 feet apart.
Pennsylvania whitetails have been infected with chronic wasting disease, or CWD, for the past eight years, but efforts to control that epidemic are similar to those deployed against the COVID-19 pandemic.
The diseases have different causes, modes of transmission and prognosis.
But once established, the diseases move alike.
“CWD and COVID-19 appear to spread in contagious diffusion, outward from a source or initial infection,” said Courtney Colley, a Pennsylvania Game Commission employee who has spent years explaining CWD to the public.
With CWD, the spread is slower.
Wildlife biologists watched it ooze north and east from Colorado, where it began in 1967. It moved through 22 states and Canadian provinces before arriving in Pennsylvania.
Started in Adams County: The first Pennsylvania deer farm where it showed up in Adams County was quarantined by the state Department of Agriculture and the game commission set up a disease management area around the farm and in areas where the disease spread.
Now three other disease management areas cover nearly 10,000 square miles in 24 counties.
CWD affects cervids, a family of species that includes deer, moose, caribou and elk. While scientists don’t think it can pass to people, the game commission recommends that hunters wear gloves when field dressing deer and refrain from shooting deer that look sick.
Deer with CWD stagger, drool and urinate frequently.
The comparisons: Colley compared other facets of the two diseases, both of which are tracked by the U.S. Centers for Disease Control and Prevention.
Quarantines on deer farms last five years because 18 to 24 months typically pass before infected deer show symptoms.
People exposed to COVID-19 have been sequestering themselves for 14 days, the incubation period.
Most people with COVID-19, perhaps 80%, develop only mild symptoms of fever, breathing difficulty and coughing, whereas all deer that contract CWD die.
COVID-19 is transmitted through aerosols released when people cough, sneeze or even talk. People also can become infected by touching a contaminated surface such as metal and plastic on which the virus can live for three to four days and then touching their faces.
Deer pass CWD through saliva, feces and urine, whereas prions — misshaped proteins that cause the disease — can live for years in soil and withstand freezing and extreme heat.
Governments have established travel bans to slow the spread of COVID-19. Likewise, the game commission prohibited importing parts of deer like the brain and spinal cord, which can spread disease, into Pennsylvania or out of disease management areas.
“With CWD, when human behaviors are not contributing, it is slow progressing, but (with) human-related movements you can see it jump 100 miles in a month. The same with COVID-19, people flying to new countries or the type of ability we have to move great distances, we’re increasing the progression,” Colley said.
Testing: Tests help identify where the disease has spread. The game commission tests deer hunted or killed by vehicles in management areas and takes random samples of deer at butcher shops in the rest of the state. The commission had to add a second lab to handle all the tests.
Scientists tracking both diseases hope for faster tests. Deer only can be tested after death so wildlife biologists seek a test that works on living animals, whereas doctors await a COVID-19 test that shows results in minutes rather than days.
After the game commission detects CWD, it lets hunters take more deer in the area and occasionally sends in certified hunters to cull deer within a mile or two of new areas where the disease appeared.
“That may seem harsh, but actually is reducing the contact rate between infected and uninfected,” Colley said. Deer, after all, don’t keep a social distance.
Further spread possible: More than 450 wild deer have tested positive, and a response plan that the game commission has drafted predicts further spread unless management strategies improve.
“The percentage of samples that test positive will continue to increase, likely exceeding 30% in wild deer within Bedford and Blair counties over the next one to two decades based on exponential growth seen in other states,” says the plan, on which the public may comment through May 7.
But the game commission achieved one success through quarantine.
The disease management area around the first deer farm where CWD showed up in 2012 has been disbanded.