A man is thought to be one of the oldest people ever to be diagnosed with the human immunodeficiency virus (HIV), at 83 years old.
The unnamed patient was admitted to a hospital in Oviedo, north Spain, in July 2019 after enduring a fever and unexplained weight loss for a month.
A heart scan showed signs of a potentially fatal infection, prompting medics to prescribe eight weeks of antibiotics. With his condition deteriorating, the man was later taken to A&E, where he was diagnosed with HIV.
After taking antiretroviral drugs, which stop the virus from replicating, the man's HIV load was "undetectable" a year later. The man, who recently celebrated his 85th birthday, is said to be well.
He has been married for 30 years, with his wife testing negative for HIV. The man has denied having sex outside of his marriage or injecting illicit drugs.
Presenting the case at the European Congress of Clinical Microbiology & Infectious Diseases, medics from the Central University Hospital of Asturias in Oviedo have warned it "serves as a reminder the elderly are not immune to HIV".
This comes after scientists from the University of Oxford announced they have administered an HIV vaccine candidate to 13 volunteers who are at high risk of catching the virus.
"This case serves as a reminder the elderly are not immune to HIV infection," said lead author Dr Enrique Garcia Carus.
"Despite a year-on-year increase in the number of older individuals being diagnosed with HIV for the first time, there is a reluctance by healthcare professionals to offer HIV tests to older people.
"Healthcare providers need to be aware that being old does not automatically equate to being at low risk, and they should be encouraged to screen patients of all ages for HIV.
"Moreover, older adults also need to be educated about preventing risky behaviours and to address HIV testing and beliefs."
In the US, just over half (51%) of those diagnosed with HIV in 2018 were aged 50 or over.
The oldest known patient lived to 100, after being diagnosed with stage three HIV aged 84 in 2004. Stage three HIV is defined as "symptomatic", with patients being at risk of catching infections they cannot fight off, as well as developing certain cancers.
Stage four HIV is "late", when the virus has severely damaged a patient's immune system, leaving them at risk of "Aids [acquired immune deficiency syndrome] defining" infections and cancers.
Older people tend to be diagnosed late in the infection's progression, when the risk of death is higher.
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The unnamed Spanish man was previously treated for high blood pressure and an irregular, abnormally fast heart beat. In May 2013, he had an aortic valve replacement – surgery to treat problems with the value, which controls the flow of blood from the heart to the rest of the body.
At the Oviedo hospital, tests revealed he had anaemia, as well as low levels of immune cells and platelets, which cause blood to clot in response to a bleed. The man's kidney function was also reduced. Nevertheless, tests for serious blood infections came back negative.
Heart scans showed his valve replacement was not working. They also flagged slight thickening of small veins, a sign of endocarditis – a life-threatening bacterial infection of the heart's inner lining.
The man was sent home with eight weeks' worth of antibiotics, but remained feverish.
After arriving at A&E when his condition deteriorated, the man was diagnosed with HIV. His CD4 count came in at 182 per cubic millimetre of blood, with anything less than 200 being a sign of advanced HIV.
CD4 cells are immune cells, which indicate the health of a person's immune system. The count of someone without HIV ranges from 500 to 1,500. People with HIV who have a count over 500 are "usually in pretty good health", while those with a count under 200 are "at high risk of developing serious illnesses".
The man also had a "high HIV viral load", with more than 180,000 copies of the virus per millimetre of blood.
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The man is thought to be one of the oldest people ever to be diagnosed with HIV, but the scientific literature is unclear.
He was started on triple antiretroviral treatment, a combination of drugs that stop HIV from replicating, allowing the immune system to repair itself. A combination of therapies helps to prevent the virus from developing resistance.
The treatment made the man's viral load undetectable, when the amount of the virus in the blood is too low to be measured. An undetectable load does not mean a patient's HIV is "cured", but they cannot pass the infection on via sex.
It is not possible to gauge exactly when the man became infected, but the Asturias medics believe it was unlikely to have happened before he was 70 years old.
HIV generally has four stages, ending with Aids. The initial "seroconversion illness" occurs when some patients experience a short period of poor health after catching HIV, often so mild it goes unnoticed or is dismissed as flu.
This is followed by the "asymptomatic stage of HIV", when a patient feels fine, often for several years. The virus is active, however, infecting new cells and damaging the immune system, before progressing to symptomatic HIV.
"We must debunk beliefs among healthcare professionals that older adults are not sexually active or use drugs, and misconceptions among older adults that they are not at risk of HIV," added Dr Carus.
"The diagnosis of HIV is often missed in older people, resulting in high rates of late presentation, which in turn substantially reduce chances of survival."