In Germany, test methods that enable the identification of an infection caused by the new influenza A/H1N1 virus, even after the symptoms have subsided or disappeared completely, have become available for the first time. The National Influenza Reference Centre (NRZ) at the Robert Koch Institute has developed two serological tests based on the detection of antibodies in the blood serum. The antibodies are produced about 2 weeks after onset of disease and can be detected months and years later.
The serological tests allow epidemiological studies to be carried out on infection rate, the proportion of severe disease, transmission and other key viral properties. "This allows us to better estimate the potential spread and to evolve targeted prevention strategies," said Jörg Hacker, President of the Robert Koch Institute.
The RKI has already prepared several serological studies, which they are now able to start with the new tests in hand. The development and evaluation of the serological test methods could, amongst other things, be based on samples that were taken by epidemiologists of the Robert Koch Institute during the course of several investigations carried out immediately after the news of the first influenza cases had emerged.
The new tests (a haemagglutination inhibition test and a microneutralisation test) complement the proven and widely used polymerase chain reaction (PCR) technology for the diagnosis of acute infections. These PCR tests identify characteristic genomic regions of the infective agent. The NRZ had established and made available to other laboratories a PCR diagnosis system for the H1N1 virus a few days after the appearance of the new infective agent.
In addition, in cooperation with the World Health Organisation, the RKI has also produced a standard for the quality assurance of H1N1 detection based on virus isolates from the National Reference Centre and the American Centre for Disease Control and Prevention (CDC). The probe was created as part of the EU Diagnosis Network "ENIVD" coordinated by the RKI and contains defined quantities of inactivated H1N1 viruses.
Laboratories around the world that are planning to implement a PCR test for the detection of the H1N1 virus can obtain the standard from the Robert Koch Institute.
The new viruses are cultured to enable their comprehensive characterisation, in particular on the molecular level. In the meantime, the complete genome sequence of two viruses isolated at the NRZ has been entered in databases that are available to researchers worldwide. The sequence information is not only important for solving diagnostic problems, but also for the examination of virus virulence, transmission and the initial assessment on the efficacy of drugs (resistance characteristics).
Resistance characteristics must also be investigated in the laboratory, which is done by testing the activity and proliferation ability of virus isolates in the presence of drugs. For the new influenza viruses (A/H1N1) investigated by the NRZ, the researchers found that so-called neuraminidase inhibitors had the best effect in terms of preventing further propagation. This confirms that results obtained in investigations carried out in the USA are also effective for viruses that have occurred in Germany.