Mumbai has been witnessing fluctuating temperatures between very high to very low in the last few days with very low humidity levels too. These changes have been attributed to the north-easterly winds. Though the cooler nights are a relief the yo-yo temperatures are a cause for concern because it is a hotbed for the spread of viruses in the environment leading to a host of respiratory diseases. Most people suffer from sore throat coughing running nose and fever. Patients with chronic diseases such as asthma and bronchitis are particularly at risk. Viral infections can cause a spasm in their airways