Signs C-19 can attack brain and other organs
We think of Covid-19 as a respiratory virus — one that simply attacks the lungs. But scientists are now wondering if it is much more than that, with a stream of medical papers being published over the past few weeks that suggests the contagion can get deep into our vascular system and even our brains.
“We are seeing a range of illness; some people develop blood clots, others heart attacks or kidney failure,” said Dr Ajay Shah, a consultant cardiologist at King’s College Hospital, London. “There are still many unknowns, but the amount of research effort that is going on to understand exactly what is happening to patients with Covid is absolutely phenomenal.”
So how does the virus attack?
Nose and throat
It is here that the infection begins, colonising the upper nasal tract, often blocking out our sense of smell, before moving down into the throat.
The cells here are rich in an enzyme known as ACE2. They enable the “spike proteins” on the surface of the virus to latch on and replicate at pace. At this point patients are highly infectious, but may not yet be suffering any symptoms. It’s one of the virus’s most devious and unusual tricks — to get its hosts to spread it to others without letting them know they are ill.
Lungs
If the body’s immune system doesn’t kill it off at this early stage, the virus travels down into the lungs.
“It’s what we would call pneumonitis — inflammation of the lung tissue — and stops the oxygen being taken up properly,” said Dr Duncan Young, professor of intensive care medicine at the Nuffield Department of Clinical Neurosciences.
This can lead to acute respiratory distress syndrome, where blood oxygen levels fall dangerously low. Ventilators can stop patients dying from lack of oxygen, said Dr Young, but “you’re keeping them alive hoping that their immune system fights the virus”.
For many people, the immune system overreacts, triggering a “cytokine storm” whereby the body attacks itself leading to multiple organ failure.
Heart and blood vessels
It is thought Covid-19 may also invade the circulatory system. Exactly how remains a mystery, but experts believe the infection may cause blood clots, heart attacks and cardiac inflammation as the virus binds to ACE2 receptors on cells lining our blood vessels. “Patients with Covid are showing signs of significant heart and vascular problems,” said Dr Shah.
Liver
Elevated enzyme levels in the liver have been observed in a significant number of hospital patients, indicating organ impairment. It’s not clear if this damage is caused by the immune system in overdrive, drugs given to fight the virus or even the virus itself.
Kidneys
In severe cases, Covid-19 can cause kidney damage — one preprint study of 85 hospital patients in Wuhan found 27 per cent had kidney failure. It is not clear whether this is because the virus attacks the kidneys directly or if it’s a response to something else.
Brain
Doctors are so far unclear on how the virus affects the brain, but studies have detailed Covid-19 patients who have suffered strokes, seizures, confusion and brain inflammation.
“Whether the virus is directly affecting the brain, or if it’s a sign that oxygen levels are just too low, we can’t be sure yet,” said Dr Young.
One case study from Japan reported traces of the virus in the cerebrospinal fluid of a Covid-19 patient who developed meningitis and encephalitis. This suggests Sars-Cov-2 could penetrate the central nervous system.