Tag: Alpha variant

COVID Variants Evolving to Improved Airborne Transmission

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A new study found that people infected with SARS-CoV-2 shed significant numbers of virus particles in their breath – and those infected with the Alpha variant put 43 to 100 times more virus into the air than people infected with the original strains. 

The researchers also found that loose-fitting cloth and surgical masks reduced the amount of virus that gets into the air around infected people by about half. The study was published in Clinical Infectious Diseases.

“Our latest study provides further evidence of the importance of airborne transmission,” said Dr Don Milton, Professor, Environmental Health, University of Maryland School of Public Health. “We know that the Delta variant circulating now is even more contagious than the Alpha variant. Our research indicates that the variants just keep getting better at traveling through the air, so we must provide better ventilation and wear tight-fitting masks, in addition to vaccination, to help stop spread of the virus.”

The numbers of airborne virus particles coming from infections with the Alpha variant (the dominant strain circulating at the time this study was conducted) was much more (18 times more) than could be explained by the increased amounts of virus picked up in nasal swabs and saliva. 
Doctoral student Jianyu Lai, a lead author of the study, explained: “We already knew that virus in saliva and nasal swabs was increased in Alpha variant infections. Virus from the nose and mouth might be transmitted by sprays of large droplets up close to an infected person. But, our study shows that the virus in exhaled aerosols is increasing even more.” These major increases in airborne virus from Alpha infections occurred before the arrival of the Delta variant, suggesting that the virus is evolving to have improved airborne transmission.

To test the efficacy of masks in reducing transmission, the researchers measured how much SARS-CoV-2 is exhaled into the air with and without wearing a cloth or surgical mask. They found that face coverings significantly reduced virus-laden particles in the air around the person with COVID by about 50%.

Co-author Dr Jennifer German said, “The take-home messages from this paper are that the coronavirus can be in your exhaled breath, is getting better at being in your exhaled breath, and using a mask reduces the chance of you breathing it on others.” This means that a layered approach to control measures (including improved ventilation, increased filtration, UV air sanitation, and tight-fitting masks, in addition to vaccination) is critical to protect people in public-facing jobs and indoor spaces.

Source: University of Maryland

Delta Variant More than Doubles Hospitalisation Risk

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In a study of more than 40 000 COVID cases, those infected with the delta variant have about twice the hospitalisation risk as those infected with the alpha variant. The findings were published in The Lancet Infectious Diseases.

The risk of hospitalisation or emergency hospital care within 14 days of infection with the delta variant was 1.45 times greater than the alpha variant. This is the first study reporting hospitalisation risk for the delta versus alpha variants based on cases confirmed by whole-genome sequencing.

Dr Gavin Dabrera, one of the study’s lead authors and a Consultant Epidemiologist at the National Infection Service, Public Health England, said: “This study confirms previous findings that people infected with Delta are significantly more likely to require hospitalisation than those with Alpha, although most cases included in the analysis were unvaccinated.”

The delta variant emerged in India in December 2020 and early studies found it to be up to 50% more transmissible than the alpha variant, which first appeared in the UK. A preliminary study from Scotland previously reported a doubling of hospitalisation risk with the delta variant over the alpha variant and it is suspected that delta is associated with more severe disease. The previous study used patients’ initial PCR test results and determined which variant they had by testing for a specific gene that is more common in the delta variant.

The researchers analysed healthcare data from 43 338 COVID-positive cases in England between 29 March and 23 May 2021. During the study period, there were 34 656 cases of the alpha variant (80%) and 8682 cases of the delta variant (20%). While the proportion of delta cases in the study period overall was 20%, it eventually encompassed two thirds of new COVID cases in the week starting 17 May 2021 (65%), effectively becoming the dominant strain in England.

Around one in 50 patients were admitted to hospital within 14 days of their first positive COVID test (2.2% alpha cases; 2.3% delta cases. After accounting for factors that are known to affect susceptibility to severe illness from COVID, including age, ethnicity, and vaccination status, the researchers found the risk of being admitted to hospital was more than doubled with the delta variant compared with the alpha variant (2.26-fold increase in risk).

It has been shown in multiple studies that full vaccination prevents both symptomatic infection and hospitalisation, for both alpha and delta variants. Indeed, in this study, only 1.8% of COVID cases (with either variant) had received both doses of the vaccine; 74% of cases were unvaccinated, and 24% were partially vaccinated. With the small number of vaccinated people being hospitalised, it is not possible to statistically compare hospitalisation risk between alpha and delta in such cases, so the results of the study apply to unvaccinated or partially vaccinated cases.

One of the study’s lead authors, Dr Anne Presanis, Senior Statistician at the MRC Biostatistics Unit, University of Cambridge, said: “Our analysis highlights that in the absence of vaccination, any Delta outbreaks will impose a greater burden on healthcare than an Alpha epidemic. Getting fully vaccinated is crucial for reducing an individual’s risk of symptomatic infection with Delta in the first place, and, importantly, of reducing a Delta patient’s risk of severe illness and hospital admission.”

Limitations to the study included some demographic groups possibly being more likely to seek hospital care, which could have biased the results, and there may have been changes in hospital admission policy during the period of the study, although adjustment for demographics and calendar time should have minimised such bias. The authors also did not have access to information about patients’ pre-existing health conditions, which are known to affect the risk of severe illness from COVID. By using age, gender, ethnicity, and estimated level of socioeconomic deprivation, they were able to account for this.

Source: Medical Xpress