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By some estimates, 2 billion people are now infected worldwide and in 2019, around 1.4 million people died from it.
It’s a pandemic infection, spread through the air – but it’s not COVID. It’s tuberculosis (or TB). Yet we are not confined for this. And we don’t stand in line for a vaccine.
Some people call tuberculosis “the forgotten pandemic”. But our knowledge of one pandemic helps us deal with the other.
Read more: Explanation: What is TB and am I at risk of getting it in Australia?
They are similar in some ways …
Tuberculosis is caused by the bacteria Mycobacterium tuberculosis. And COVID is caused by SARS-CoV-2, a virus. They are quite different microorganisms. But it’s easy for them to overlap in people’s minds.
Tuberculosis and COVID are infectious diseases that commonly affect the lungs. Both are transmitted between people primarily through aerosols, when infected people cough, sing, or release them into the surrounding air.
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So some of the things we’re used to doing for COVID-19 – like wearing masks and getting good ventilation – also work to prevent the spread of TB.
However, there are some important differences between them, which means our public health responses can look very different.
Read more: “Kissing Can Be Dangerous”: How Oddly Familiar Old TB Tips Look Today
… but not in the others
We all know COVID so well. So when I talk to people about TB, I started to point out three key differences between infections.
1. Tuberculosis is less contagious
Tuberculosis is much less contagious. While COVID (especially strains like the Delta variant) can be transmitted after brief or “fleeting” contact, this is rare for TB.
Typically, tuberculosis control programs around the world often suggest that you need to be in close contact with an infectious person for more than eight hours before this risk accumulates to the point where you need to be tested. .
This means that people are more likely to spread the infection within their homes or immediate families rather than in stores.
2. Symptoms of tuberculosis take longer to appear
With TB, the “window” between exposure and discomfort, called the incubation period, is much longer.
Infections can lie dormant (or “latent”) in the body for several months or years before people feel unwell. But almost everyone who gets sick with COVID has been infected in the past two weeks.
We do not ask TB contacts to isolate themselves at home because we cannot predict when they might become ill. It certainly wouldn’t be ethical or realistic to isolate people for months or years, just in case. Fortunately, people with latent TB cannot pass the infection on to others in the meantime.
3. We have TB treatments to help stop the spread
Since we don’t know how long it takes between a person getting infected and not feeling well with TB, you would think this would be a big deal.
But we have effective treatments to give to people with latent tuberculosis. These help prevent them from developing active disease.
These treatments, especially antibiotics such as isoniazid or rifampin, can significantly reduce the risk of contact disease.
For COVID, we do not yet have treatment for people who are infected but do not have symptoms (called post-exposure treatments) to minimize the risk of the virus spreading.
Some have been tried, but so far none has convincingly proven to work.
What about vaccines?
Perhaps the biggest difference in our response to these pandemics is that we have a variety of effective COVID vaccines available.
For tuberculosis, we rely on a century-old vaccine, BCG (short for Bacille Calmette-Guérin), which remains one of the most widely used vaccines in the world.
While it protects young children from the most severe forms of tuberculosis, the vaccine appears to offer much less protection for adults.
The BCG vaccine, unlike COVID vaccines, is a live vaccine, which means it contains live (but weakened) bacteria. Therefore, it cannot be given safely to people with immunosuppressive conditions, such as HIV, as they could become infected with it. This means that its use is limited in some people who are most in need of protection.
Tuberculosis vaccine may protect against COVID
Maybe the BCG vaccine and COVID will come full circle. The BRACE trial, launched by the Murdoch Children’s Research Institute in Melbourne, studies whether the BCG vaccine could protect against COVID infection.
This investigation was prompted by a long history of research showing that the vaccine also improves our immune responses to other conditions such as viral infections.
We don’t know yet if this will work, as the study is ongoing. Nearly 7,000 healthcare workers worldwide at risk of COVID exposure have been recruited for the trial.
Read more: Could BCG, a century-old vaccine against tuberculosis, protect against the coronavirus?
Whether or not BCG is found to prevent COVID, there is no doubt that we need new and more effective tuberculosis vaccines.
Although we have a growing number of potential vaccine candidates, there is still no alternative to our century-old BCG today.
The huge amount of global activity in COVID vaccine development has also spurred calls for more effort and funding to develop new tuberculosis vaccines.
We hope that these will lead to more effective and safer options, and be powerful tools to eliminate tuberculosis. Hopefully we don’t wait another 100 years.
Read more: Tuberculosis kills as many people each year as COVID-19. It’s time to find a better vaccine
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