14/07/2015 8:21 AM IST | Updated 15/07/2016 8:25 AM IST

In The Age Of Travel, Tuberculosis Knows No Borders

In this Monday, Feb. 3, 2014 photo, senior chest physician Dr. A.K. Upadhaya looks at x-ray results of patient Shyam Lal, suspected to have tuberculosis (TB), at Lal Bahadur Shastri Government Hospital at Ram Nagar in Varanasi, India. India has the highest incidence of TB in the world, according to the World Health Organization's Global Tuberculosis Report 2013, with as many as 2.4 million cases. India saw the greatest increase in multidrug-resistant TB between 2011 and 2012. The disease kills about 300,000 people every year in the country. (AP Photo/Rajesh Kumar Singh)

The recent episode of an air passenger who travelled from India to the United States, while suffering from extensively drug-resistant tuberculosis (XDR-TB*), has raised a public health scare. The passenger, after landing in Chicago, travelled by car to visit relatives in three states before seeking medical care and being diagnosed with XDR-TB. She has been isolated and is currently on treatment at the US National Institutes of Health. Public health officials are now working to locate everyone who has possibly been exposed to the infection, including fellow air passengers.

This is not the first time that such an incident has happened in the U.S. In 2007, a person who knew he had multidrug-resistant TB (MDR-TB*) flew on multiple flights between the US and several countries in Europe. Significant resources were deployed to locate fellow air passengers and screen them for infection.

These incidents highlight how dangerous strains of TB can move around the world in a matter of hours, placing unsuspecting fellow passengers and other contacts at risk. It is imperative to prevent such incidents from reoccurring.

"TB can move around the world in a matter of hours, placing unsuspecting fellow passengers and other contacts at risk."

Tuberculosis is an airborne infectious disease. Once someone inhales the bacteria that cause the illness, that person can unknowingly live with a TB infection for years before actually getting sick and potentially transmitting the infection to others. This makes drug-resistant TB a particularly insidious disease -- a time-bomb that can silently lie dormant for a while and then activate to cause public health havoc.

While TB transmission in aircrafts is rare, it is possible. The risk of transmission increases with the duration of travel, the proximity of the sick individual to other passengers, and the amount of bacteria being coughed into the air. The task of finding and evaluating those who were in contact with a passenger with infectious TB -- a rapid response necessary to protect individuals as well as the health of the broader public -- is highly complex and resource intensive.

The risk of transmission during air travel is expected to rise as the number of international passengers, currently 3.3 billion annually, is projected to double by 2034 according to the International Air Transport Association. The fastest-increasing markets for air travel include countries grappling with high burdens of TB, such as Brazil, China, India and Indonesia. Together these countries are home to approximately 3 million people who develop TB each year, according to the World Health Organisation (WHO).

In response, some developed countries, such as the UK, have made TB screening mandatory for travellers from countries with high burdens of TB who intend to stay longer than six months. The rationale of this approach is debatable, as it leaves out the large number of short-duration travellers who could nevertheless have or develop symptoms of TB.

"We need intensive efforts to create awareness about drug-resistant TB among both the public and healthcare providers, so people are diagnosed early."

Instead, we need more pragmatic approaches to reducing the TB risks posed by international travel. In the case of the passenger with XDR-TB who travelled from India to the US, reports indicate that she had been diagnosed as early as 2006 and had since then even travelled to Australia. It is possible that her physician had not communicated the risks involved in flying. In other cases, the affected person may not get a timely diagnosis despite symptoms or may delay seeking medical care.

Nearly half a million people develop multidrug-resistant TB each year -- and only one in five receives a diagnosis and treatment, according to WHO. In many places, testing for drug-resistance remains rare. We need intensive efforts to create awareness about drug-resistant TB among both the public and healthcare providers, so people are diagnosed early. We also need better communication between healthcare providers and patients, to help them reduce the risk of transmitting the infection.

Most importantly, we need to do a better job of preventing drug resistance from emerging in the first place. Countries with high burdens of drug-resistant TB need to improve the quality of TB care, which will reduce the likelihood of resistance developing. History has shown that this will take political commitment, including increased public health funding for TB plus investment in research to develop new diagnostics, drugs and treatment regimens.

No individual country can face down drug-resistant TB on its own. Both wealthy and developing countries need to support each other in this effort, because TB knows no borders.

*MDR-TB is a strain of TB resistant to the two most effective drugs, Rifampicin and Isoniazid. Such strains need prolonged treatment, for up to 2 years, with "second-line" TB medications. If inadequately treated, MDR-TB can develop resistance to second-line medicines, becoming XDR-TB. There are very limited treatment options for XDR-TB and extremely poor outcomes.

The views expressed by the authors are personal.

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