According to a two-year study conducted by doctors of King Edward Memorial (KEM) Hospital and Tata Institute of Fundamental Research, both during the monsoons and the non-monsoon period, men between 15-40 years of age were found to be more prone to malaria. Retrospective records from hospitals in Mumbai like King Edward Memorial hospital, Wadia hospital, Kasturbha hospital and pathology laboratories were the source of clinical malaria data while active surveillance data measured parasite prevalence in the general populace. Clinical malaria was assessed from the case records of patients showing malaria-like symptoms. Parasite positive patients from this cohort represented clinically diseased individuals seeking medical intervention. A majority of the data came from the Out Patient's Department (OPD) of King Edwards Memorial (KEM) Hospital. Most of the patients (80%) were treated in the OPDs and did not need hospitalization. The number of females and children visiting KEM hospital for malaria-like symptoms was lower than males (ratios of males: females -2.2:0.2; children:adults- 0.1:0.1). The Kasturba Hospital for Infectious Diseases, Mumbai, had a higher representation of women and children (males:females 3.5; children:adults:0.15) and hence its OPD records were also included, said Dr Shobhona Sharma, Prof of Biology and expert in malaria of TIFR. Data was also collected from private hospitals and pathology laboratories in Navi Mumbai, which offer higher-cost medical services. This was to control for biases caused by socio-economic factors. Relapsed/recrudescent patients, repeat blood samples, and pregnant women were excluded from the analysis, added Dr Sharma. Active surveillance records were sourced from a Navi Mumbai Municipal Corporation urban health project 13 (UHP 13). Municipal health workers routinely visit residential areas, slums, construction sites, schools, etc. Blood smears are collected from individuals who report fevers, headaches, or other malaria-associated symptoms during the visit or the preceding fortnight. Smears are also requested of their family and immediate neighbours. Parasite positive persons from this group represent individuals whose symptoms did not necessitate hospital-based medical intervention. The twin city cohorts were largely non-overlapping, said Dr Sharma. General observations are that most fatal cases occurring in Mumbai due to vivax infection also incur large liver damage. A combination of malnutrition, pre-existing liver damage (due to several factors such as alcohol, smoking and eating oily food) and other immunosuppressive conditions such as worm co-infection, may precipitate fatality, even though infection through the parasite Plasmodium vivax, is otherwise a very manageable disease, said Dr Shobhana. The anthropophilic Anopheles stephensi is the main malarial vector in this urban region. "Distribution patterns of clinical malaria vis