Jan. 25 (UPI) -- Cases of seasonal viruses in northern California fell by roughly two-thirds in the spring and early summer of 2020 compared with years past, even as the COVID-19 pandemic raged through the region, a study published Monday by JAMA Network Open found.
Just under 10% of nose and throat samples tested for bugs such as the flu, as well as coronavirus and rhinovirus, the viruses behind the common cold, came back positive during April, May and June 2020, the data showed.
During the same period in 2014 through 2019, just under 30% of collected samples tested positive for these viruses.
Stay-at-home orders instituted in the region last spring due to the COVID-19 pandemic most likely contributed to the decline, researchers said.
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"The data are clear and not surprising, [because] public health measures like shelter-in-place, frequent hand washing, respiratory etiquette, including masking, and social distancing prevent the spread of respiratory viruses," study co-author Dr. Elizabeth Partridge told UPI.
"We know what to do to curb the spread of [COVID-19], [and] we need the support of government, community leaders and the personal commitment of our citizens to practice these public health strategies," said Partridge, an assistant clinical professor of infectious diseases at the University of California-Davis.
There have been "lower-than-usual" numbers of flu cases nationally so far this winter, with just 136 people across the country hospitalized due to the seasonal virus through Jan. 16, according to the U.S. Centers for Disease Control and Prevention.
That figure typically numbers in the tens of thousands, and is likely down because measures taken to reduce the spread of COVID-19 also help contain the flu and other seasonal viruses, experts have said.
For this study, Partridge and her colleagues analyzed data on more than 46,000 samples collected for viral testing between 2014 and 2020.
From March 25 through July 31, 2020, 9.9% of samples tested came back positive for seasonal respiratory viruses, down from 29.9% during the previous five years, the data showed.
However, 30.4% of samples tested between Jan. 1 and March 24, 2020 -- or prior to the implementation of COVID-19 control measures -- came back positive, down slightly from the 33.7% of prior years, the researchers said.
"These are lessons we already know but are brought into stark relief with the emergence of a novel respiratory virus: [that] these basic public health strategies can curb the spread of all organisms that are transmitted by droplets, including seasonal influenza," Partridge said.
"Perhaps after the pandemic, mask-wearing in public during the respiratory viral season will become routine in the U.S., as it is in many Asian countries," she said.
