NEW DELHI: An increasing number of countries, including some in Asia, are now reporting Tamiflu-resistant H1N1 virus. The worrying development, according to WHO, has seen 12 countries, including China and Singapore, reporting a mutation in the virus. India has not reported the mutation so far.The changes in the virus reported in samples are making these strains of swine flu resistant to oseltamivir or Tamiflu, the antiviral of choice globally.Such cases have also been found in Japan, US, Hong Kong, Denmark and Canada. While India is monitoring these reports closely, it will begin exit screening of pilgrims bound for Saudi Arabia for Haj as the desert nation is refusing entry to anyone with even common cold. Saudi authorities are insisting on certificates stating that Haj pilgrims are completely free of any influenza infection.Changes in the virus are also being tracked closely as scientists are concerned that new strains may make the vaccines being developed at a feverish pace infructuous. As of now, WHO fears Tamiflu resistance may be more widespread than officially reported.Going by available data, majority of the resistant cases were reported where oseltamivir was given as preventive medication to people exposed to the flu but who had not tested positive themselves. Some cases were a result of treatment of mild illness as well as ���immuno-compromised ��� patients or persons whose immune systems were working imperfectly.India has so far not reported such a mutation. ICMR director general Dr V M Katoch told TOI, ���We have been constantly sequencing genes in H1N1 to mark any form of mutation.���