Covid-19 Who is most at risk?

Who is most at risk?

Adults over the age of 60.

Age is one factor in whether someone dies from Covid-19. This is because past the age of 60, someone is more likely to have heart disease, cancers and other medical conditions such as diabetes, which mean the body is less able to fight off the infection. The proportion of Covid-19 deaths by age groups is:

• 90% are over 60. (52% are over 80 and 39.7% are between 60 and 79.)
• 7% are between 40 and 59, while 0.72% are between 20 and 39
• 0.077% are between 0 and 19.

Very few children become severely ill with the virus

Children of all ages may catch the disease but are likely to have milder symptoms and a lower chance of severe disease than adults. They are also less likely to pass on the infection. Australian researchers have identified a number of factors which may explain this.

• Children have strong undamaged cells in their blood vessels which prevent inflamation and clotting, and their blood clotting system is different.
• They have elevated levels of vitamin D.
• Their immune system is fast acting. They are more likely to be infected with other pathogens such as colds and and other germs picked up in the playground. This can build a strong natural immune system.
• They have often been recently vaccinated for other diseases, including MMR. This effectively 'trains' the immune system and keeps it 'firing on all cylinders'.
• They have fewer ACE2 receptors, which the virus uses to infect cells. ACE2 becomes more prevalent as they grow up.

However a coronavirus-related inflammatory syndrome occasionally occurs in children. Symptoms include high temperature, low blood pressure, a rash and difficulty breathing; some also had tummy pain, vomiting or diarrhoea, and inflammation of the heart and abnormal blood test results. Experts say these are signs the body becomes overwhelmed as it tries to fight of the infection.

People who are overweight or obese.

Obesity increases the risk of a number of diseases, (e.g. heart disease, cancer and type 2 diabetes). The more overweight, the more fat you carry, the less fit you are and the lower your lung capacity. So it's a bigger struggle to get oxygen into the blood and around the body, which impacts on the heart and blood flow. Being overweight, you also have a demand for more oxygen. This can be a serious problem during a respiratory infection like coronavirus; the obese body  becomes overwhelmed by the lack of oxygen. Overweight and obese people in intensive care are more likely to need assistance with breathing and support with kidney function.

An enzyme called ACE2, present in cells, is the main way for the virus to enter the body. Higher levels of this are thought to be found in adipose (fatty) tissue, which could explain the higher risk of catching the disease and a higher risk of being ill with it.

The ability of the body to fight off the virus (the immune response) is not as good in people who are obese, due the inflammation driven by immune cells called macrophages which invade our fat tissue; they interfere with how our cells respond to infection. This can lead to a 'cytokine storm' - a potentially life-threatening over-reaction of the body's immune system which causes inflammation and serious harm.

And there can be challenges in managing these patients in intensive care: (a) it is more difficult to intubate them (put onto a ventilator); (b) to scan them because of weight limits and (c) they may be more tricky to turn, or prone, in order to relieve their breathing.

Men

Men are slightly more likely to die, but in some countries this is may be due to higher smoking rates in men which compromise lung function. New research shows that men have higher levels of the ACE2 receptor on cell surfaces, which binds to the new virus, allowing it to enter and infect cells. Men have a higher level of ACE2 found in the heart, kidneys and tissues lining blood vessels, and especially high levels in the testes. 

Black, Asian and Minority Ethnic (BAME) populations 

UK data (May 2020) suggests that 35% of critically ill patients are from BAME backgrounds. The following factors appear to be important.

Many BAME populations come from lower socioeconomic backgrounds and work in public-facing occupations (healthcare, cleaners, restaurant workers, transport and delivery workers and other public services). They are likely to be in inter-generational households, with more of the aged still at home, and religious activities with large numbers of attendees. Between 15% and 30% live in overcrowded households in contrast to just 2% of white British households.

They have an increased risk of certain diseases (e.g. diabetes and heart disease).  People from BAME backgrounds have more of a specific type of fat tissue which is prone to macrophage invasion (see section on obesity and the ACE enzyme), have elevated rates of diabetes, and may therefore be more vulnerable to the virus.

Pregnant women

Pregnant women may be at higher risk for severe infection but data is not yet available. 
Those with a pre-existing condition (e.g. high blood pressure, diabetes, heart disease and lung disease) are more likely to die.

People with disabilities that limit activity.

People (over the age of 9) with a disability that limits activity account for nearly 60% of UK Covid-19 deaths, but form only 16% of the population. (Study reported 18 Sept. 2020.)

Certain blood groups may be more likely to have severe infections

Ethnic and national populations can have different proportions of blood groups. Worldwide the rarest blood type is AB, while Rh negative blood types are found in 0.3% of Asian populations and 15% of European populations. Proportions can also differ within a country. In the UK, the ratio is O = 48%   A = 38%   B = 10%   AB = 3%. In southern England: O = 44%   A = 45%   B =  8%    AB = 3%.

A study in China (March 2020) found that the normal population ratio was A = 31%   B = 24%   AB = 9%   O = 34%, while the ratio for those with the virus was A = 38%   B = 26%  AB = 10%  O = 25%.  Researchers concluded that "blood group A had a significantly higher risk for Covid-19 compared with non-A groups, whereas blood group O had a significantly lower risk." (Their findings were published before peer review, so need to be treated with caution.) In the US, another study found a similar pattern but only among rhesus positive patients. NB. Susceptibility to infection does not necessarily equal risk to getting seriously ill. Other studies on infection rates and severity of illness relating to blood groups are currently in progress in several countries.

Another study of patients in Italy and Spain with Covid-19 respiratory failure found two genetic variants associated with the severity of their disease. One cluster of six genes had included genes that regulate ACE2. The other variant was the ABO blood group system. However, an analysis of medical data from thousands of people in the Boston area of the US found no association.

Note: Some other viruses are blood-group dependent. People with type A blood seem to be more susceptible to hepatitis B and HIV, while people with type O are somewhat protected against catching SARS.

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