1 Division of Epidemiology and Communicable Disease, New Delhi, India.
2 MRC Centre for Global Infectious Disease Analysis, School of Public Health, Imperial College London, London, UK.
3 Indian Council of Medical Research, New Delhi, India.
4 Division of Epidemiology and Communicable Disease, New Delhi, India; National AIDS Research Institute, New Delhi, India. Electronic address: pandas.hq@icmr.gov.in.