Detecting flu and its various types has got easier,with scientists at the National Institute of Virology (NIV) trying out a cocktail of primers and probes to simultaneously identify various kinds of influenza virus in a single test reaction tube.
It breaks away from the single-test-for-single-pathogen mould to detect common and serious influenza types through a single test,Dr M S Chadda,Deputy Director of NIV told Newsline.
The technique known as multiplexing uses primers (that can magnify the virus) and probes (fluorescent dyes) that are attached to the DNA sequence of the virus. In a single tube where the throat swab sample is placed,it is now possible to identify influenza types be it H3N2 (form of Influenza A) H1N1 (swine flu),the milder type of influenza B and even its lineage.
All reagents are commercially available and what we have really done here is use a mix of these primers and probes so that various types of influenza can be simultaneously detected, says Chadda. In the usual method,two to three tests in real-time polymerase chain reaction (PCR) are conducted to find the influenza strain. So if the sample tested negative for Influenza B,other tests had to be performed to detect Influenza A. A single test costs US $50 and hence by simultaneously trying to identify the viruses in a single test tube will not be cheaper but also save time. The test results can be available within six hours,says Chadda.
Meanwhile,influenza surveillance data reveals that mild type of influenza B virus is prevailing in the country this year. Barring March and April that saw an unusual spurt in swine flu in India and other parts of the globe,this year saw a mild form of influenza prevailing. Kerala,however,has been witnessing a fair amount of swine flu activity with nearly 255 samples being tested from June 30 till July 6. There is a 5-10 per cent rate of transmission of H1N1 virus and this trend has been continuing in Kerala since April,says Chadda. In other parts of the country including Pune,there has been a milder strain of influenza B (common cold,cough and fever),says Chadda.
Influenza surveillance,which was intensified from 2003 saw the Indian Council of Medical Research setting up a network of five centres,which were expanded to 10 in 2009. NIV is the focal centre where isolates are sent from across the 10 centres in the country. This is the third year of the second phase of the surveillance project funded by Centre for Disease Control,USA and ICMR. In the first phase,over 20,000 samples from OPDs and hospital patients was collected from 2004-2009 and we saw a variety of viruses co-circulating during this phase. In the second phase from 2010,22,400 samples were collected and the dominant virus for was the pandemic influenza, Chadda added.