COVID-19: Do we really know all the facts?Sunday, May 31, 2020
BY DR ERNEST MADU & DR PAUL EDWARDS
WE continue to experience the effects of the novel coronaravirus SARS-CoV-2 and the resultant disease COVID-19.
As we gain greater clinical experience, findings and patterns that were not well appreciated early in the epidemic have become clearer. We thought that we would discuss some of the more interesting findings this week to bring our readers up to speed on what is known to date.
COVID-19 is not just lung disease
Early during the pandemic, it became clear that patients who were critically ill with COVID-19 usually had severe infection of the lungs. This was not unexpected, given the fact that the coronavirus family (to which the SARS-CoV-2 virus belongs) is known to predominantly affect the respiratory system. Early reports from China were that the heart and kidneys were frequently involved, and this involvement was a predictor of poor outcome. What has become clearer with time is the fact that for patients with severe disease, almost any organ in the body can be involved and there are in fact many ways in which the SARS-CoV-2 virus can result in morbidity and mortality. Some of this organ involvement can be related to direct actions of the virus, but the actions of the virus in causing inflammation, clotting and blood vessel damage are also important.
As we have discussed in an earlier article in this column, severe COVID-19 infections can result in overactivity of the immune system. During severe infection of any type, the immune system is activated. This activation results in several processes that together target the invading organism. However, in some individuals, certain infective processes can result in excessive immune activation, causing damage to infected and non-infected body tissues. You can imagine the response of the police to criminal activity in a neighbourhood. Sometimes, the police may respond with overwhelming force that leaves collateral damage in their wake and in such situations, innocent citizens in the neighbourhood may also fall victim to the response that was targeted at the criminal elements. This is also the nature of immune response in some instances, in which case the host becomes part of the collateral damage.
Chemicals produced during immune activation (cytokines) can serve to directly damage organs, for example the heart. Another mechanism by which the SARS-CoV-2 virus can damage organs is by causing inflammation in the wall of blood vessels. This inflammation can lead to occlusion of the blood vessels, leading to rashes in the skin or strokes in the brain. Studies have also revealed that the clotting system can be inappropriately activated in COVID-19 disease. This can result in clotting in the legs or lungs (deep-vein thrombosis and pulmonary embolism). The brain and nervous system are frequently affected, with seizures, strokes, changes in level of consciousness and inflammation all being reported. Interestingly, loss of taste and smell can be an early sign of COVID-19 disease occurring prior to lung symptoms. This finding is likely related to nerve damage from the SARS-CoV-2 virus. Inflammation of the liver has also been reported, along with the isolation of virus particles in the stool. Hospitalised patients commonly display conjunctivitis (red eyes). Skin rashes of various types are noted. Often reported is the so-called COVID toes or fingers, which is thought to be related to inflammation of the blood vessels supplying the fingers and toes.
COVID-19 and children
Throughout the COVID-19 epidemic one interesting finding has been the age range for symptoms of the disease; young persons appear to be protected in terms of not being symptomatic or having severe disease. But over the past two months in North America and Europe, a peculiar manifestation of COVID-19 disease has been noted in children and adolescents. This appears to be associated with widespread inflammation of the body and blood vessels and appears to be similar to an inflammatory disease of blood vessels known as Kawasaki disease. So far, clusters of patients have been reported and it is unclear how commonly this occurs. It is now known as Multisystem Inflammatory Syndrome in Children. It appears to occur after the acute illness has resolved, and usually the children are no longer infectious. The inflammatory process can affect many organs including the heart, lungs, kidneys, brains, skin, and eyes. Common symptoms include fever, abdominal pain, diarrhoea, vomiting, red eyes, lethargy, and rash. It is thought that this syndrome is related to immune system abnormalities brought on by the SARS-CoV-2 virus. Children with this syndrome are often quite ill, requiring ICU care. They are commonly treated by immune suppression.
Can one contract COVID-19 again after recovery?
There have been some questions raised as to whether is possible to get reinfected with the SARS-CoV-2 virus, after recovery. Generally, after a viral infection the immune system of the body has “a memory” of the virus. This memory results in the production of antibodies and T-cells which serve to recognise the virus, should it enter the body again. This, generally, makes it unlikely that the same virus can cause infection again while that “memory” is active. There is, however, a lot that is not known. The first is the duration of this immunity. Some viruses in the coronavirus family that cause the common cold are associated with an immune response that lasts for a year. Some respiratory viruses, ie influenza A and B, can change over time from what is known as genetic drift. This results in the immune system of the body no longer recognising the virus.
So far, two studies have raised the reinfection question with patients who were infected with SARS-CoV-2, had clinical recovery with negative testing, and had virus particles recovered after presumably healing. One study in South Korea has been investigated by the WHO and it is thought that the virus particles that were found represented pieces of the virus in dead lung cells, and were not thought to be infectious. A study from China is currently being evaluated. At this point in time it is thought to be unlikely that a patient will be reinfected with the SARS-CoV-2 virus in a short space of time. It also does not appear that the SARS-CoV-2 virus undergoes significant genetic drift that would prevent recognition by the immune system. However, the strength of the immune response and the duration of immunity remain areas in which more research is needed.
Social risk factors for COVID-19 infection
As COVID-19 infection has spread throughout the western world, it has become clear that race, ethnicity, social status, and other environment factors all play a role in the likelihood of becoming infected with the SARS-CoV-2 virus or becoming seriously ill if infected.
Data from the United States and Britain have found that the black population is disproportionately affected. Data from the state of Michigan in the United States found that the African American population accounted for 33 per cent of the COVID-19 cases and 40 per cent of deaths, despite representing just 14 per cent of the population.
In the United Kingdom, members of the black population were four times as likely to die of COVID-19 disease than those in the white population. The Hispanic population in the United States is also disproportionately affected by COVID-19 disease. Indigenous peoples in many areas of the world have higher rates of COVID-19 infection thant the non-native population. The reasons for this disproportionate effect are many. Non-white populations, particularly in the United States, have higher rates of chronic disease and often more limited access to medical care. There are also higher numbers of them working at occupations that make it difficult to social distance, ie retail, delivery etc. The indigenous populations tend to have higher incidences of multiple generations living together in a single household. There may be issues of inadequate water supply or limited availability to local health care as well.
Other social groups who have proved to be at elevated risk include nursing home residents or patients who are institutionalised. Many of these patients are at elevated risk levels given their age. Additionally, these individuals are often dependent on caregivers who take care of many individuals and who sometimes work in several institutions. This situation puts them at risk as one infected individual can result in rapid spread to many at-risk individuals, as has been seen in Washington State, New York, and Sweden.
The realisation that COVID-19's spread occurs efficiently in prisons has resulted in many low-risk offenders in the United States being allowed to serve their sentences at home to reduce crowding and the likelihood of disease. Homeless shelters in the United States have also been places of elevated risk for SARS-CoV-2 infection. Lastly, various occupations in which people work together in close quarters have been found to be associated with higher risk of infection. In Jamaica we have had our experience with the call centres. In the United States, meat packing plants have been found to serve as foci for infection in otherwise low-risk communities.
As our experience with this novel coronavirus continues, it is certain that new and interesting data will continue to emerge. For our part, it is important that we continue to follow measures that will keep us safe and free of infection.
Continue to stay safe.
Dr Ernest Madu, MD, FACC and Dr Paul Edwards, MD, FACC are consultant cardiologists at Heart Institute of the Caribbean (HIC) and HIC Heart Hospital.
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