COVID-19 severity depends on transmission, NIH study suggests

A new study from the National Institutes of Health suggests that COVID-19 can have more of a severe impact on the lungs if the virus is transmitted through the air versus a contaminated surface.

Researchers used Syrian hamsters to highlight the difference. The scientists exposed the hamsters to SARS-CoV-2, the virus responsible for COVID-19, via aerosol droplets and contaminated surfaces, known as fomites. 

Results showed that aerosol exposure directly deposited the virus deep into the lungs. However, fomite exposure resulted in coronavirus being found in the nose. 

Scientists said, either way, the virus ended up in the hamsters’ lungs. However, lung damage was more severe in hamsters who were exposed to COVID-19 via aerosol droplets. 

RELATED: CDC COVID-19 map shows most of US under high community transmission

Another part of the study focused on the animal-to-animal transmission of the novel coronavirus through the air or fomites. Results showed airbone transmission of the virus was more contagious than fomite transmission.

An additional experiment, using air flowing from infected to uninfected animals, supported the finding: Reversing the airflow from uninfected to infected animals greatly reduced transmission efficiency.

Researchers said their results prove that airborne droplets are a key route for COVID-19 transmission.

Scientists from NIH’s National Institute of Allergy and Infectious Diseases conducted the experiments at Rocky Mountain Laboratories in Hamilton, Montana. They published their study in Nature Communications.

According to FOX 5 DC, the majority of the U.S. was under a high level of COVID-19 community transmission based off the latest map from the Centers for Disease Control and Prevention. The latest map on their website - most of which was colored red - shows data from between Tuesday, Aug. 10 and Monday, Aug. 16.

The rise in COVID-19 cases have many cities and states reissuing mask mandates, particularly in indoor settings. The seven-day average of new reported cases has topped 140,000, an increase of 64% from two weeks ago and the highest level in more than six months.

Federal officials are extending into January a requirement that people on airline flights and public transportation wear face masks, a rule intended to limit the spread of COVID-19. 

The CDC changed course in July on some masking guidelines, recommending that even vaccinated people return to wearing masks indoors in parts of the U.S. where the delta variant of the novel coronavirus is fueling infection surges.

RELATED: LA County mandates masks for 'mega events' like concerts, sports games regardless of vaccination status

Citing new information about the variant’s ability to spread among vaccinated people, the CDC also recommended indoor masks for all teachers, staff, students and visitors at schools nationwide, regardless of vaccination status.

Most new infections in the U.S. continue to be among unvaccinated people. So-called breakthrough infections, which generally cause milder illness, can occur in vaccinated people. When earlier strains of the virus predominated, infected vaccinated people were found to have low levels of virus and were deemed unlikely to spread the virus much, CDC Director Dr. Rochelle Walensky said.

According to the latest numbers from CDC, more than 169 million Americans are fully vaccinated, representing 51% of the country’s total population. 

The Associated Press contributed to this report. This story was reported from Los Angeles.