What causes cold and flu?

Causes of cold and flu. The viruses responsible for colds are spread from person to person as droplets in the air from sneezing or coughing, or from touching infected surfaces then transmitting the viruses from the hands to the mouth. Handshakes or touching a door handle are possible routes for transmission of cold viruses. Infected people can spread the viruses from two days before the illness and up to four days after the symptoms start. Colds can occur all year round but are more common in the winter months.

People living in residential or nursing homes, and people with the following conditions are at risk:

• Chronic chest problems such as chronic bronchitis and emphysema
• Heart disease
Kidney diseases and kidney failure
• People with reduced immunity, such as people with HIV or people who have had their spleen removed