(Bloomberg ) Tuberculosis, the deadly lung disease purged from most rich nations decades ago, is hitching a ride back in unsuspecting migrants. Most cases go undetected, quietly spreading TB from Stockholm to Sydney.
A latent form of the bug that isn't detectable by standard X-ray screening can hide in bone marrow, lying dormant for years, researchers said in a study published last week. After the infection springs back to life, its carriers can spread it anew via sneezing and coughing. As global migration accelerates, an increase in cases of TB among immigrants has prompted governments to review screening procedures. It's also boosting sales for Dutch-based Qiagen NV (QGEN), whose test for latent TB has become its fastest-growing product.
"If we go on doing what we've always done, which is just to treat active TB, we'll go on getting what we've always got, which is more and more TB," said Ajit Lalvani, chair of infectious diseases at Imperial College London. "We're not stemming the tide or tackling the root cause, which is the latent TB," he said in a telephone interview.
Latent TB was the most-commonly diagnosed infection among migrants globally, and was found in almost half of those headed for the U.S., researchers from the Atlanta-based Centers for Disease Control and Prevention said in December.
The resurgence in TB is a growth opportunity for Qiagen, based in Venlo, Netherlands, which got the QuantiFERON TB test with its $361 million acquisition of Australia's Cellestis Ltd. in August 2011. The product is tapping a global market that JPMorgan Chase & Co. estimates at more than $500 million a year, supported by immigration screening and mandatory TB testing of U.S. health-care workers.
Sales of the test expanded more than 20 percent last year on a constant currency basis from $55 million in 2011, Qiagen said when reporting earnings on Jan. 29, without being more specific.
Revenue from the product will continue at that pace for the next few years, and will probably overtake sales of Qiagen's test for human papillomavirus, the pathogen that causes cervical cancer, Chief Executive Officer Peer Schatz said on a call with analysts. The HPV diagnostic has been the company's biggest seller since 2007.
Qiagen forecast 2013 earnings that exceeded analysts' estimates, based partly on sales prospects for QuantiFERON. The stock has climbed 27 percent in the past year, including reinvested dividends, compared with a 16 percent gain in the Stoxx 600 Health Care Index. Qiagen has a market value of 3.7 billion euros ($4.9 billion).
QuantiFERON is "a bit off-radar" for investors, Adrian Howd, an analyst at Berenberg Bank in London, said in a telephone interview. "It could have more significant growth potential than the market currently assumes."
The test identifies latent TB by reacting with a chemical called interferon gamma in a person's blood. It's designed to supersede the 120-year-old Mantoux skin test, which can return a false positive result in people who've been vaccinated against TB, and sometimes leaves permanent scarring.
While most countries in the Organization for Economic Cooperation and Development test migrants for active TB, only about half screen for the latent form, Lalvani and colleagues wrote in the journal Emerging Infectious Diseases in September.
The U.K., where TB is 20 times more common among immigrants than those born in Britain, changed its screening guidelines in 2011 to recommend that immigrants from countries where TB is widespread be offered a latent TB test, either with QuantiFERON or a rival product made by Abingdon, U.K.-based Oxford Immunotec Ltd., the company Lalvani founded.
Other European nations with large groups of immigrants from Africa such as France, Sweden and Denmark will be the next big markets for the test, said Christian Stoeckigt, Qiagen's associate director of scientific affairs for QuantiFERON in Europe and the Middle East.
Among the European Union's 27 member countries, all but six recorded an increase in TB among immigrants in 2010, according to a report last year.
More countries may follow suit. Governments in the Middle East are considering latent TB screening for foreign laborers, many of whom come from the Indian subcontinent, he said.
In a survey of almost 8,000 migrants, latent TB was detected in 22 percent, and 43 percent of those headed for the U.S., CDC researchers wrote in the journal Clinical Infectious Diseases in December. Latent TB is "the largest challenge to TB elimination," researchers from the CDC wrote in a separate study last year.
While Qiagen's $20 test costs more than the Mantoux test, its higher reliability reduces false positive results, eliminating unnecessary follow-up visits and cutting costs, said Stoeckigt.
A trial at the University of Chicago found that QuantiFERON helped save $80,000 in its first year of use, he said.
About 16 million latent TB tests were performed in the U.S. last year, including about 1.9 million QuantiFERON tests, Stoeckigt said. Most of the rest involved the Mantoux skin test.
Tuberculosis sickened about 8.7 million people in 2011 and killed 1.4 million, making it the second-deadliest infectious disease behind AIDS, according to the World Health Organization.
About one third of the world's population has latent TB, in which the immune system walls off the bacteria that cause the disease, according to the Geneva-based WHO. Investigators writing in the journal Science Translational Medicine last week found that the bacteria that cause the disease hide out in stem cells in bone marrow, evading detection by the immune system.
In about 10 percent of those people, the bug activates, causing disease and raising the risk the carrier will infect others through coughing and sneezing.
Activation can be caused by HIV infection, organ transplantation, diabetes or the use of drugs that suppress the immune system, such as AbbVie Inc. (ABBV)'s rheumatoid arthritis treatment Humira, the world's second-best selling drug. In many other cases, scientists don't know what rouses the pathogen, Lalvani said.
Ridding the body of TB -- active and latent -- is key in stopping its spread, especially as new drug-resistant strains emerge. In Australia, patients with hard-to-treat TB spend about six months in the hospital, costing an average of A$250,000 ($260,000) per case, said Justin Denholm, an infectious diseases doctor and TB researcher at the Royal Melbourne Hospital.
Australia had 1,222 cases of active TB in 2011, of which more than 90 percent were among people who were born abroad and almost certainly brought latent TB with them, Denholm said.
"If you want to reduce TB incidence from where we are now, you have to tackle latent TB," Denholm said. "It's the critical missing piece of the puzzle."