Airborne SARS-CoV-2 more efficient than SARS, MERs viruses, study shows

Aerosolized SARS-CoV-2, the virus that causes COVID-19, remained infectious for as long as 16 hours, according to a study published yesterday in Emerging Infectious Diseases.

Using nebulizers and a custom-built rotating drum, US researchers aerosolized the viruses once each in primate head-only exposure chambers or 30-liter rodent chambers in four aerobiology laboratories.

They measured the short-term aerosol efficiencies of SARS-CoV-2 and compared them with those of SARS-CoV and MERS-CoV, the related coronaviruses that cause SARS (severe acute respiratory syndrome, and MERS (Middle East respiratory syndrome), respectively. They also used scanning electron microscopy to determine if the virus remained intact over time, indicating infectiousness.

The findings showed that SARS-CoV-2 is at least as or more efficient than SARS-CoV and MERS-CoV and that it stays infectiousness at sizes that can be inhaled over short distances, which is not the case for the other two coronavirus. It also persists in aerosols longer than would be expected on the basis of previous studies of other hardy viruses such as monkeypox, the authors said.

The data suggest that aerosol transmission of SARS-CoV-2 may be a more important mode of transmission than previously thought, the researchers said, noting that people generate aerosols continuously through breathing and that aerosol production increases during respiratory diseases and loud talking.

"A fraction of naturally generated aerosols falls within the size distribution used in our experimental studies [less than 5 micrometers], which leads us to conclude that SARS-CoV-2–infected persons may produce viral bioaerosols that remain infectious for long periods after production through human shedding and airborne transport," they wrote.
Jun 22 Emerg Infect Dis study

Scientists: More than 80% of US COVID-19 infections likely undetected

A surge in influenza-like illness (ILI) in the United States in March suggests that more than 80% of COVID-19 infections went undetected, according to an analysis published yesterday in Science Translational Medicine.

Using the Centers for Disease Control and Prevention's (CDC's) ILI surveillance data and disease models, researchers estimated that if one third of patients infected with SARS-CoV-2 had sought care, testing would have revealed another 8.7 million new COVID-19 infections from Mar 8 to 28. Only 32% of people infected with the novel coronavirus sought care, the authors calculated. The official US tally now stands at over 2.3 million cases, which include only lab-confirmed infections.

Combining the excess ILI counts with the start of community transmission in the United States suggests that the epidemic was doubling at least every 4 days, at least twice as fast as originally thought. In March, coinciding with an unprecedented spike in ILI in some states, the COVID-19 death doubling rate was 3 days. The patterns of non-flu ILI and COVID-19 cases also closely matched.

"We analyzed each state's ILI cases to estimate the number that could not be attributed to influenza and were in excess of seasonal baseline levels," lead author Justin Silverman, MD, PhD, of Penn State University, said in a university press release. "When you subtract these out, you're left with what we're calling excess ILI— cases that can't be explained by either influenza or the typical seasonal variation of respiratory pathogens."

In the study, the authors point to limited test availability, high false-negative rates, and asymptomatic or mild infections not requiring medical attention as the reasons for the undercount of COVID-19 cases.

"We emphasize the importance of testing these findings with seroprevalence data and discuss the broader potential to use syndromic surveillance for early detection and understanding of emerging infectious diseases," they wrote.
Jun 22 Sci Transl Med study
Jun 22 Penn State University news release

Cyclospora outbreak linked to bagged salads sickens 46 more people

An outbreak of the parasite Cyclospora linked to bagged salads has grown to include 46 more people and one more state and now includes 122 cases in seven states, according to a CDC update today.

The outbreak, which the CDC said on Jun 19 had already sickened 76 people in six states, was traced to garden salads containing carrots, red cabbage, and iceberg lettuce sold at Aldi, Hy-Vee, and Jewel-Osco stores in Illinois, Iowa, Kansas, Missouri, Minnesota, Nebraska, South Dakota, and Wisconsin.

Nineteen people have been hospitalized as the result of the outbreak, but none have died. Illness-onset dates ranged from May 11 to Jun 15.

Iowa has the most cases, with 54, followed by Illinois (30), Minnesota (13), Wisconsin (9), Nebraska (8), and Missouri (7). Patients range in age from 16 to 92 years, with a median age of 63.

The CDC said that these products have been recalled and should be discarded: All Jewel-Osco Signature Farms Garden Salad sold in Illinois, Indiana, and Iowa; all Hy-Vee Brand Garden Salad sold in Illinois, Iowa, Kansas, Missouri, Minnesota, Nebraska, South Dakota, and Wisconsin; and all Aldi Little Salad Bar Brand Garden Salad sold in Arkansas, Illinois, Indiana, Iowa, Michigan, Minnesota, Missouri, North Dakota, South Dakota, and Wisconsin.

Cyclospora is a parasite that can be found in uncooked produce, and infection results in watery diarrhea that can last for weeks if untreated.
Jun 23 CDC update

Italy reports low-path H7N1 and H5N3 avian flu outbreaks in poultry

Veterinary officials in Italy yesterday reported avian flu outbreaks in poultry involving two low-pathogenic strains, H7N1 and H5N3, according to separate notifications from the World Organization for Animal Health (OIE).

The H7N1 outbreaks occurred in the middle of April at two commercial turkey farms in Veneto region in the northeast of the country. All 14,300 susceptible birds were culled to control the spread of the virus. So far, the source of the virus isn't known. Italy reported the last outbreak involving the strain in August 2019.

More recently, tests at an ostrich farm in Lombardy turned up low-pathogenic H5N3 in the north central part of the country. The outbreak began on Jun 15, sickening 5 of 132 birds. All were culled as part of the outbreak response. Investigators haven't yet determined the source of the virus. The last appearance of the virus in Italy was in April, according to the OIE report.
Jun 22 OIE report on H7N1 in Italy
Jun 22 OIE report on H5N3 in Italy