Ever since The New York Times spelled out the beginning of Aids paranoia with its first ominous report of a strange 'gay cancer' in 1981, the developed world's media have searched desperately for the next great medical threat. Such fears have been stoked by the Sars outbreak of 2003 and dire predictions of avian flu. Yet while these threats can't sensibly be ignored, another danger lies in the complacency that allows previously controlled diseases to sneak in through the back door. In this respect, a new study has given New York a major wake-up call. According to a report published by the New York University School of Medicine, 15 per cent of Asians living in New York City - about 100,000 people - are chronically infected with the hepatitis B virus, therefore putting them at high risk of deadly diseases such as liver cancer and cirrhosis in later life. Official estimates from the World Health Organisation state that more than 500 million people around the world are infected with hepatitis and that, according to the US Centres for Disease Control and Prevention, the impact of the disease will double over the next decade, such is its prevalence in poorer countries. Although hepatitis is recognised as being endemic in parts of Asia and Africa, the NYU's recent findings have surprised those who believed hepatitis to be yesterday's problem in the US. For most Americans this is the case, thanks to an extensive vaccination programme carried out in the 1980s and early 90s. Yet, among New York's east Asian immigrant population, there are few who have benefited from such luxuries, resulting in one person in seven carrying the hepatitis B virus. According to a 2000 census, the city's Asian immigrant population of 800,000 is the largest in the US, with nearly half of that number originating from China. Factor in those who have entered the country illegally since then, and that figure is likely to be much higher. The rapid growth of immigrants from places such as China and Korea in the past 20 years has meant that the city now faces a potential healthcare crisis as it becomes burdened with the result of inadequate healthcare and education overseas. Thanks both to the disease's long-term dormancy, coupled with a general lack of knowledge, the majority of the Asian-born adults screened in and around the New York area were unaware that they were infected. This echoes last year's discoveries made by George Lau Ka-kit, hepatology professor at the University of Hong Kong, who tested 500 Cheung Chau residents in November and found 10 per cent were hepatitis B carriers. Dr Lau said that 80 per cent of Hongkongers were not aware of their health problems. Such ignorance is a major source of frustration for doctors, especially in the context of the woeful healthcare system in the US, in which the vast majority of immigrants cannot afford health insurance and are therefore vulnerable to a disease that could otherwise be treated with prescription drugs. 'Most of the people we diagnosed as being infected did not have insurance and lived beneath the poverty line, so how could they afford any care?' says Dr Henry Pollack, who co-authored the report published in the Centres for Disease Control and Prevention's journal, Morbidity and Mortality Weekly Report. A mitigating factor for this study, however, was in its sense of amnesty. In offering free treatment with no questions asked about legal immigrant status, Dr Pollack and his team may have also encouraged some who knew they were infected but could not afford to do anything about it. Placing advertisements in ethnic newspapers for people to come forward for free tests and treatment, the researchers discovered a 'large number of persons infected who will be in need of care later', said Dr Pollack. 'We've estimated that there are as many as 100,000 Asian-Americans in New York who might be infected. If you were to figure out the costs involved in caring and following that group, it's going to be quite high. We're talking hundreds of millions of dollars.' The NYU report is widely regarded as the most comprehensive analysis of the problem to date in the New York area, as well as being the first to illustrate not only the number of people infected, but to also analyse this data. Men aged between 20 and 39 were found to be more likely to have the virus, and men were generally twice as likely as women to be infected. Sixty-one per cent of those screened were born in China, and 30 per cent were born in Korea. The remainder, hailing from elsewhere in Asia, had much lower rates of infection than the Chinese immigrants, who were 35 times above the infection rate in the general public. The issue has not yet become a full-scale medical emergency, thanks to the relative slowness of the disease, yet it points to a looming healthcare crisis and a possible backlash against those entering the country illegally. 'Could someone look at this and say we have to prevent certain groups of people from coming in to the US? I'd hope that this would not happen,' said Dr Pollack. 'In China there is a large amount of discrimination against those infected. People can't get jobs. You have to look at this as a kind of global problem.' The team behind this latest study are pointing to how their interception has helped the system. 'We haven't done a cost-effective analysis of it, but looking at the vaccination programme we've screened over 4,000 and vaccinated close to 500 people, which alone has saved the medical care system large amounts of dollars,' said Dr Thomas Tsang, also a principal investigator in the study and chief medical officer of the Charles Wang Community Health Centre in New York's Chinatown. 'With all the media campaigns we've done and all the public health talks, we've educated 50,000 people. That's an immeasurable amount of money in terms of saving potential future threats.' Why the prevalence of hepatitis B is so high in China is still a mystery to scientists, and the team behind the study plan to work with their overseas counterparts in an effort to tackle the root of the problem. In Asia, the biggest threat would seem to be ignorance and the lack of a comprehensive vaccination programme, as mothers pass the disease to their newborns. As this study and similar studies in Hong Kong have found, the majority of those diagnosed are unaware that they're infected. 'When you look at the Chinese patients we screened, they were grouped from various regions within China that had spectacularly high rates, particularly those from Fujian province, where we had a figure of 29 per cent with chronic infection,' said Dr Pollack. The findings correlate with figures on the mainland, and compare badly with those of the mainstream US. The Centres for Disease Control and Prevention have estimated that just 0.4 per cent of all Americans have chronic hepatitis B. 'The point that we're trying to make is that the data shows that it isn't a huge problem among average, mainstream Americans,' said Dr Tsang. 'But within segments of communities it's a significant problem.' Medical advances have given doctors an array of new drugs which, while treating infection, don't cure the disease. Hong Kong has made significant contributions in vaccines, the most recent being the Sci-B-Vac drug created at the University of Hong Kong.