It follows reports this week of more than 30 cases in the United States, France, Spain and the United Kingdom, which fit this description. A doctor in California is now claiming that a new retrovirus (belonging to the same family as HIV) has been found in one of the patients. Two scientists in New York are also believed to have evidence of such a virus.
The illness appears to be rare, but if a new virus is responsible it has worrying implications for public health officials, particularly over screening of blood supplies.
Dr Michael Merson, director of the WHO's global programme on Aids, told the International Conference on Aids in Amsterdam that there would be an 'immediate follow-up' of the claims. 'WHO will bring together people from everywhere who have reported the cases and experts to look at the information, analyse it and see what should be done next.' The meeting will be held in Geneva within months, he said.
The conference, attended by the world's leading Aids researchers, was 'hijacked' yesterday by Dr Sudhir Gupta, chief of Basic and Clinical Immunology at the University of California, Irvine, who announced that he had found a new virus - Human Intracisternal Retrovirus - in a 66-year-old woman with severe immunodeficiency and a form of pneumonia common in Aids. Her 38-year-old daughter, who is healthy, also has the virus, he said. Neither woman had any risk factor for Aids and neither had tested positive for HIV-1, HIV-2, or any other human retrovirus.
Aids experts expressed cautious scepticism over Dr Gupta's work, which is to be published next month in the Proceedings of the National Academy of Sciences.
Dr Max Essex, of the Harvard School of Public Health, questioned whether Dr Gupta had found viral particles rather than a whole new virus. Thousands of such particles from retroviruses are present in the body and have never been linked to disease.
Dr James Curran, leader of the Centers for Disease Control's HIV-Aids programme, said that investigation of cases was now a priority. The CDC this week confirmed that it was investigating six cases of the Aids-like illness in the absence of HIV. Dr Jeffrey Laurance, of Cornell University in New York, has five patients. He is thought to have found some evidence of a retrovirus but is refusing to discuss the results until publication of a scientific paper.
Dr David Ho, director of the Aaron Diamond Aids Research Center in New York, said that over several years he had treated 11 patients with the Aids-like illness but no HIV. An enzyme produced by retroviruses was present in some of them, he said.