TB spreads via close, prolonged contact with infected person

The Ministry of Health (MOH) announced on June 24 that about 170 people at Block 2 Jalan Bukit Merah had tested positive for tuberculosis (TB).

The tests were offered to residents and workers at the block after seven people there were diagnosed with the disease between February last year and March this year.

The Straits Times answers some questions about the disease.

A TB is an infectious disease caused by bacteria called Mycobacterium tuberculosis.

The airborne disease spreads when an infected person coughs, sneezes or breathes, and a person nearby inhales the expelled infectious droplets in the air.

Transmission of TB often requires close and prolonged contact with an infected individual.

TB does not spread via contact with items or surfaces touched by an infected person, unlike for Covid-19.

People living in the same household and close workplace colleagues are at a higher risk of being exposed to TB and getting infected.

A There are two types - latent and active.

For some people, the immune system might be unable to kill the bacteria when they enter the body, but is able to prevent them from spreading in the body.

This is known as latent TB, where the bacteria are suppressed but "asleep" in the body.

Those with latent TB are not ill, will not have any symptoms and are not infectious to others.

However, latent TB can later become active TB when immunity wanes. The United States Centres for Disease Control and Prevention estimated that, without treatment, 5 per cent to 10 per cent of infected people would develop active TB at some point in their lives.

Active TB, also known as TB disease, is when the body fails to kill or contain the bacteria, making the person ill.

An individual with active TB will have symptoms and can potentially spread the disease to others.

About half of the people who develop active TB will do so within the first two to three years of being infected.

A Symptoms include a persistent cough that lasts three weeks or longer - which might include coughing up phlegm or blood, low-grade fever, night sweats, fatigue, weight loss and chest pain.

A While it primarily affects the lungs - what is known as pulmonary TB - it can also affect other parts of the body like the central nervous system, bones, joints and the abdomen, referred to as extra-pulmonary TB.

A Those with close and prolonged contact with an infectious person may be called to undergo blood tests and possibly a chest X-ray.

A According to a World Health Organisation report last year, about a quarter of the global population have been infected by Mycobacterium tuberculosis, although only a relatively small proportion will develop active TB in their lifetime.

TB infections are not uncommon in Singapore, with the prevalence among those aged 70 to 79 being as high as 29 per cent.

There were 1,306 new cases of active TB among Singapore residents last year. In 2020, the figure was 1,360. The probability of developing active TB is higher among people with underlying medical conditions like diabetes, as well as those with weakened immune systems due to age, among other factors.

A Active TB is potentially fatal without treatment, with an estimated 1.5 million people dying from it globally in 2020.

However, with treatment, it is highly curable and death is rare.

A Treatment usually involves taking a combination of antibiotics for six to nine months.

MOH states on its website that more than 95 per cent of people with active TB are cured if they take all the medication as prescribed until completion.

It is crucial to complete the course of antibiotics as prescribed, even if symptoms improve, failing which there is a higher chance of a relapse and a greater possibility of TB becoming resistant to first-line anti-TB drugs.

Drug-resistant TB is more difficult to treat, as less effective drugs will then need to be used, likely prolonging the course of treatment and considerably decreasing the chances of being cured.

Multi-drug resistant TB has fatality rates of as high as 30 per cent to 40 per cent.

Those with latent TB infections might also be started on a course of preventive treatment to avoid the development of active TB disease in the future.

A Those with active TB become non-infectious after two weeks of treatment. While infectious, they should stay at home to prevent infecting others.

When among other household members, they should wear a face mask and cover their mouth with a tissue when they cough or sneeze.

Those who display symptoms like a prolonged cough should seek medical attention early.

A The Bacillus Calmette-Guerin vaccine is primarily used against TB.

In Singapore, it is given to newborns soon after birth, as part of the National Childhood Immunisation Schedule.

While it protects against other forms of TB like TB meningitis, which affects the brain lining, it offers limited protection against pulmonary TB.