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How likely are you to catch COVID from a member of your household?

Catriona Harvey-Jenner
·6-min read
Photo credit: Flavia Morlachetti - Getty Images
Photo credit: Flavia Morlachetti - Getty Images

From Cosmopolitan

As far as contagious viruses go, COVID is bad. One of the most virulent pandemics in world history, coronavirus has caused the deaths of almost two million people, has shut down industries, and has forced people to stay inside the safety of their own homes for months on end.

A year into the pandemic, we're now seeing the emergence of new variants. One spreading around the United Kingdom this winter has been found to be around 70% more transmissible than the original, meaning it's even easier to catch. With that in mind, it would be fair to assume that once one person in a household contracts coronavirus, it's simply a case of if and not when other residents get it. But anecdotally, we know that's not always the case.

"I've lived with my boyfriend since long before the pandemic started. Back in March he got a few symptoms including loss of taste and smell, but since widespread testing wasn't available at the time, neither of us were confirmed to have had it," says 27-year-old Daniella.

"However, when we were both offered antibody tests last year as part of a trial, my partner came back as having antibodies - conforming he'd had COVID - while I didn't show any indication of having them. Despite us being in the same house the whole time he had it in March, and not distancing from each other at all, I never caught it " she recalls.

Photo credit: dowell - Getty Images
Photo credit: dowell - Getty Images

So how can this kind of thing happen? You'd think that living in close quarters and sharing a kitchen, bathroom facilities and - in the case of couples - a bed, would all mean that passing on COVID was pretty much a dead-cert. But Dr Rachel Jarvis, General Practitioner at HCA UK's Roodlane Medical, explains why COVID sometimes slips through the net between household members. "There is thought to be a roughly 40% chance of catching COVID if you are living in a household with a positive COVID case," notes the doctor, adding that it's "difficult" for experts to know exactly why this is the case.

"It can be to do with the amount of virus someone is exposed to," says Dr Jarvis. If this 'viral load' is minimal, it stands to reason that a person may not get ill from it at all. New large-scale research from Oxford University has found that the less viral load an individual has (so, the less virus they have present in their nose and throat), the less infectious they are, which goes some way to explaining why some people pass COVID-19 on and others do not.

Another reason for people managing to avoid contracting coronavirus when it's present in their own home can be due to immunity. "Some household members may have immunity following previous exposure to COVID, and not realising that they had it," says the GP. "Around a third of people who have COVID develop no symptoms at all. These people can still be spreading it unwittingly, which is why it is so important to keep following government guidance on limiting contact with others, wearing masks and washing hands," she adds.

Photo credit: Getty Images
Photo credit: Getty Images

There's also research to suggest that a small proportion of the population is lucky enough to have pre-existing immunity to COVID-19 without ever having caught this specific coronavirus themselves. Dr Jarvis says this is "not surprising" because "coronaviruses are not new, just our attention to them." She goes on to explain: "The variant that emerged in late 2019 has proved to be a version which is particularly successful at spreading and sadly one which has proven to be quite deadly to some of the most vulnerable people."

The doctor makes the point that "a virus' sole purpose in existence is to keep replicating and spreading; they constantly mutate to try to get better at evading our defences and successfully spread on to the next host." The thinking is that people who have come into contact with a similar coronavirus in the past may have built up an immunity to the current virus, and therefore might not be at such risk of catching it. But of course, there's no easy way of knowing this, and even if you're immune you can still theoretically pass on the virus, so it's vital everyone takes the same hygiene and social distancing precautions to prevent further transmission.

How does COVID spread?

Coronavirus can be spread in two ways: direct or indirect. "Direct spread refers to the inhalation of viral particles, which can be spread in to the air when an infected person coughs, sneezes or breathes. These are then breathed in by other people bringing particles in to your nose, throat and lungs, where the virus multiplies and can cause the main COVID symptoms of fever, cough and altered sense of smell," says Dr Jarvis, adding: "Other bodily fluids, such as tears and faeces, are thought to be able to cause COVID infection. Flushing the loo can create an aerosol effect so you could help to reduce spread by putting down the lid before you flush.

Photo credit: GK Hart/Vikki Hart - Getty Images
Photo credit: GK Hart/Vikki Hart - Getty Images

Indirect spread, on the other hand, refers to "becoming infected by touching an infected surface and then touching your face," explains Dr Jarvis. "This is why the government encourages you to think about 'Hands, Face, Space'. Social distance, frequent hand washing and wearing a mask all helps to reduce the likelihood of viral transmission."

The important thing to remember is that you will never know or see who you are spreading a virus to. "Even if you are fit and well, you may unknowingly act as part of a chain of infection that eventually leads to a vulnerable person dying," says the doctor.

How can you reduce the likelihood of spreading coronavirus inside the home?

Okay, so we all know the precautions we should take in public, but what if someone you live with has just received a positive COVID test result? You probably want to do all you can to minimise your chances of getting it, too. The key thing, which is a pretty obvious one, is minimising the contact the sick person has with other inhabitants. "Ideally, they should stay in a well-ventilated room on their own, including to eat their meals. If possible, they should use their own bathroom and own towels," says Dr Jarvis.

Beyond that, the GP recommends that all members of the household should regularly wash their hands and they should try to stay at least 2 metres apart, as well as letting fresh air in to blow away any virus particles. "All members of the household should wear a mask if they are around the other inhabitants. This is not a magic bullet but it could help to reduce the chance of infection spreading," advises the doctor, adding that "shared surfaces should be sanitised at regular intervals with disinfectant spray or wipes."

Photo credit: gilaxia - Getty Images
Photo credit: gilaxia - Getty Images

Follow these rules, and you'll go some way to reducing your chance of catching COVID too. Because the less people who get it, the less people can spread it - and that way, the less people will become seriously ill from it.

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