The death of the unvaccinated woman in March earlier this year is believed to be the first documented case of its kind. The woman, who died in Belgium, is suspected to have contracted both the Alpha and Beta variant from two different people.
Scientists are now warning that, although rare, dual infections are happening.
Dr Anne Vankeerberghen, lead researcher from the OLV hospital in Aalst, Belgium, said the co-infection likely hastened her symptoms.
She said: “Both these variants were circulating in Belgium at the time, so it is likely that the lady was co-infected with different viruses from two different people.
“Unfortunately, we don’t know how she became infected.
“She was a lady who lived alone, but she got a lot of helpers coming in to care for her.
“Whether the co-infection of the two variants of concern played a role in the fast deterioration of the patient is difficult to say.”
The evolved forms of the virus are believed to have originated in Kent and Brazil respectively.
Both Alpha and Beta strains are classed as “variants of concern” and have mutations that differ from the base version of the virus.
Recent data suggests the Pfizer/BioNTech and AstraZeneca vaccines were 96 percent and 92 percent effective against hospitalisation from the Delta variant respectively after two doses.
However, a study compiled by Israel’s Ministry of Health released last week suggests the Pfizer vaccine becomes less effective at dealing with variants after six months – dropping to around 64 percent efficacy.
The Delta variant, first identified in India, is the most prevalent strain in the UK and US.