Two-plus years into the pandemic and with more than 485 million Covid cases reported, infectious disease scientists are learning every day about the long-term effects of this disease. While much more will be discovered in time, one thing’s already clear: even mild infections can leave people at high risk for severe health complications.
With any kind of infection, there’s the acute stage — the part we think of as the infection, where antibiotics or antivirals might be needed to help the immune system beat out the invading pathogen — but there can also be effects that aren’t noticeable for weeks, months, or even years. The virus that causes chicken pox, for example, can remain dormant in the body for years, re-emerging much later to cause shingles. The human papillomavirus (HPV) begins as an infection, but in the long run can lead to cancer.
The earliest known Covid infections occurred fewer than 30 months ago, but already clinical studies are revealing a host of long-term health ramifications associated with the disease. Here’s a quick overview.
Last month, scientists reported a concerning trend: one year after infection, people who had Covid faced a 40% higher risk of developing diabetes than people without Covid.
Though the biological connection between the infection and the onset of diabetes is not yet clear, the study was large enough to generate compelling results. Researchers used clinical databases run by the US Department of Veterans Affairs, analyzing more than 180,000 veterans who tested positive for Covid and comparing them to two separate healthy control groups with more than four million veterans apiece. None of the veterans had diabetes at the beginning of the study period, and participants’ health outcomes were followed for about a year, on average.
The 40% increased risk of developing diabetes could be associated with damage to the pancreas caused by the virus responsible for Covid, though that has not yet been proven.
Even during the initial infection, some people cite what has been called “Covid brain” — trouble paying attention, forgetfulness, and a general feeling of brain fog. But now scientists know that Covid’s effects on the brain are much more durable and damaging. A recent study found that changes in the brains of people who had Covid were equivalent to as much as 10 years of natural aging.
Scientists used MRI brain scans of 785 participants in the long-term UK Biobank health study; approximately 400 people were diagnosed with Covid and the remaining 380-plus people served as healthy controls. For each participant, the team had two scans; the Covid patients tested positive between the two scans, allowing researchers to compare pre- and post-infection MRI results to understand how the disease affected the brain.
Among Covid patients, the scientists found more reduction in gray matter associated with neurodegeneration, more tissue damage, and an overall reduction in brain size compared to the healthy controls. This held true for patients with mild and severe Covid infections. Overall reduction in brain size mirrored the normal loss associated with one year to 10 years of aging.
Heart Attack and Stroke
Studies have also shown that the risk of heart attack or stroke increases significantly in the days and weeks following a Covid infection. In one large study, scientists analyzed outcomes for nearly 87,000 people in Sweden after their Covid diagnosis. They compared those results to outcomes for nearly 350,000 people who were not infected.
The difference was clear. Among people who had Covid, heart attack risk was three to eight times higher in the days following infection than in people without Covid. The risk of stroke increased three- to six-fold. While those risk numbers declined over time, they remained higher than usual at least one month after diagnosis.
Even in the early days of the pandemic, it was clear that while most people got over the infection in a matter of weeks, some individuals with Covid had ongoing symptoms that just didn’t go away. Now known as “long Covid,” this condition causes a broad range of symptoms that look more like a chronic disease than a one-time infection.
Severity of the initial infection seems unrelated to long Covid; people who suffer from this condition often had mild symptoms or even no symptoms at all. Hallmarks of long Covid include shortness of breath, fatigue, heart palpitations, headaches, rash, joint and muscle pain, diarrhea, dizziness, hair loss, and attention disorder.
In the U.S., long Covid is now considered a disability under the Americans with Disabilities Act.
In other words, even as we eagerly look for signs that the pandemic is receding, the sad reality is that the disease burden of Covid will be with us for a very long time. From people who barely survived Covid to those who didn’t even know they had it, the virus will continue to make millions of people sicker than they should have been.