It’s one thing to imagine myself dying – or recovering – from severe Covid-19 in the comfort of my own home, surrounded by my family; and quite another to contemplate how this could affect them.  How can we assess the risk to their own health? What precautions can be taken? And how could I begin to convince them that they should feel not the slightest sense of obligation to stay at my side, nor the slightest guilt should they choose not to jeopardise their own health and to withdraw from contact with me?

It is beyond the scope of this blog to explore the knotty ethical and emotional issues attendant upon a decision to stay at home, but perhaps I can pose other questions that can be usefully considered. For instance, what is likely to be the risk to the life or health of my partner, or that of a devoted child or friend, in exposing them to a considerable dose of the virus? What are the implications of repeated or continuous exposure in our particular circumstances? What level of PPE would be advisable and available? Is the amount of air circulation important? How would we manage tasks like turning, washing, and dealing with waste? How would we involve healthcare professionals?

In trying to come to grips with the risk of mortality from the virus, it’s become clear from the plethora of statistics that there’s not much clarity to be had at the moment. It can be bewildering to read that

Infection rates among healthcare workers vary greatly between countries, with fewer than 1% in Singapore and more than 30% in Ireland

followed by

In the UK, across those care homes where managers reported at least one case of coronavirus, we estimate that 20% of residents in those care homes have tested positive for COVID-19, while 7% of staff tested positive between 26 May and 20 June 2020

followed by

Of those who reported working in patient-facing healthcare or resident-facing social care roles, 1.58% tested positive for COVID-19 on a swab test up to 27 June 2020 (those aged between 16 and 74 years old). By comparison, the percentage of people reporting not working in these types of roles testing positive for COVID-19 on a swab test was lower at 0.27%.

As for mortality rates, the  ONS occupational risks survey states that the rate for male care workers and home carers was 71.1 deaths per 100,000 (0.071%) for residents of England and Wales aged 20 to 64 years(deaths registered between 9 March and 25 May 2020).The comparable mortality for female care workers and home carers was 25.9 deaths per 100,000 women (0.026%).

This compares to 19.1 deaths per 100,000 men of the working population, and 9.7 deaths per 100,000 women.

The ONS goes on to clarify that these figures ‘do not prove conclusively that the observed rates of death involving COVID-19 are necessarily caused by differences in occupational exposure. In the analysis we adjusted for age, but not for other factors such as ethnic group, place of residence or deprivation. Additionally, the analysis only considers the occupation of the deceased. We have not taken account of the occupations of others in the household.’

It’s impossible to extrapolate any firm figures from these surveys, in that they cover different specifics, but they all indicate much lower infection/fatality rates than I was expecting. At the moment it seems that the statistical information about the risk to any individual in their specific situation is not available. Indeed the risk may well prove impossible to gauge due to the complexity of this disease. We do know that it’s affected, among other factors, by age and gender; by health conditions like obesity, diabetes, raised blood pressure; by ethnic group, deprivation, crowded residences; and by the availability and standard of PPE and other precautions. If I myself, for instance, were considering caring for my partner, taking into account my being male and over 70 (just!) but with no co-morbidities and with reasonable PPE, I can only hazard a guess of mortality risk between 0.5% and 3%.

An additional factor would be the amount of exposure to the virus. Anyone staying at home with Covid would need to be isolated from the rest of the household, yet this would pose difficulties in many homes. The concept of ‘viral load ’is much talked about, but it’s important to understand that it has two different meanings. One refers to the number of viral particles you are exposed to, perhaps better termed ‘infectious dose’; and the other (the medical use of the term) is the number of viruses present in your throat and nose at the time of having an antigen test. How are these two different meanings related? Presumably as the virus replicates in the nose and throat, the number present may depend on more factors than the number taken in; for example, the length of time since the particles were inhaled, and the effectiveness of your defence mechanisms. The number may also depend on the time since infection (https://www.medscape.com/viewarticle/934147 ) and the way the test is performed. Against this background, I would think that the current test can’t indicate the size of the initial dose of virus.

This was the subject of a  CEBM rapid review early in the pandemic.  Since then, there have been several papers and articles published on this topic, including :

What We Do and Do Not Know About COVID-19’s Infectious Dose and Viral Load
Doctor’s Note: Does a high viral load make coronavirus worse?
Coronavirus: How ‘viral load’ and genetics could explain why young people have died from Covid-19
Impact of SARS-CoV-2 Viral Load on Risk of Intubation and Mortality Among Hospitalized Patients with Coronavirus Disease 2019

Perhaps it is time for another review by CEBM of the current evidence, since the above seems to be inconclusive.

‘Viral shedding’ is another term used to describe a person’s infectivity, and this appears to vary at different stages of the disease. In addition, different circumstances have variable risks of generating an infective dose, especially if they involve aerosol formation, as with the use of fans, CCAP machines, failure to mask the patient, poor air circulation, and poorly functioning PPE.  Advice to carers at home contains much useful information, but does not go into this kind of detail.

PPE of different levels of protection are recommended in different settings by NICE. This urges the use of plastic aprons, fluid-resistant surgical masks, gloves and eye protection in a domestic setting. Rigorous PPE at the level used in ICUs is not, on the whole, a practical proposition, though I suppose it shouldn’t be ruled out. Randomised trials of non-pharmacological prophylactic techniques, such as the nasal-pharyngeal sterilising solution of povidone-iodine, are just beginning, and it will be interesting to see if any show a reduction in the viral load.

Does staying at home increase the risk of spreading the virus in the community? Health workers will need to come to my house to minister to me if I choose not to go into hospital, and many of these will also be visiting other vulnerable people. Would more health workers be involved in my care than in a hospital, and would standards of PPE at home be sufficient to keep them safe? Is there a chance that I would actually be seeding the pandemic by not being isolated in hospital?

It would be good if these questions can be debated and resolved, at least partially, during this lull in the pandemic here in the UK. We need more research to inform choices about the implications for family, carers and the wider public of looking after patients in a home setting.