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The US National Institute of Allergy and Infectious Diseases (NIAD) has announced the development of a novel oligonucleotide microarray (also known as gene chips or DNA chips) for the diagnosis of pathogenic infections (see press release). An international team, including researchers from the US, Canada, Hungary, Germany, Spain and the World Health Organization, has created the ‘GreeneChip’, an array of some 30,000 oligonucleotides representing samples of distinctive genetic material from thousands of human pathogens, including viruses, bacteria, fungi and parasites. Passing human fluid or tissue samples over the array allows any pathogenic genetic material that is present to adhere to the complimentary sequence on the array; signals from such interactions can be interpreted to discover which type of pathogen is present.

The GreeneChip reportedly performs as well as conventional diagnostic methods and is much faster. Rapid diagnosis of the infectious agent is important clinically, to optimise treatments, and also for public health, to allow control of outbreaks of infectious disease, but quite different infectious agents may produce the same, non-specific symptoms giving no indication of the likely cause of disease. Director of the Greene Infectious Disease Laboratory at Columbia University Dr. Ian Lipkin said: "Methods that simultaneously screen for multiple agents are important, particularly when early accurate diagnosis can alter treatment or assist in containment of an outbreak…to address the challenges of emerging infectious diseases and biodefense, public health practitioners and diagnosticians need a comprehensive set of tools for pathogen surveillance and detection" (see press release).

The GreeneChip is described in the CDC's online publication Emerging Infectious Diseases [Palacios G et al. (2006) EID 13(1)], with information about how the system is used for ‘molecular pathogen surveillance and discovery’, validation with samples from patients with respiratory disease, hemorrhagic fever, tuberculosis and urinary tract infections, and its use in the investigation of the cause of death of a health worker, who died during an outbreak of Marburg hemorrhagic fever in Angola from an illness similar to viral haemorrhagic fever. Testing with the GreeneChip failed to show any evidence of the Marburg virus, but rather indicated that the worker had been infected with Plasmodium falciparum, the etiological agent of malaria, which can cause similar symptoms.