Norovirus, also known as 'winter vomiting disease' causes gastroenteritis and is highly infectious. The virus is easily transmitted through contact with infected individuals from one person to another.
Outbreaks are common in semi-enclosed environments such as hospitals, nursing homes, schools and offices and can also occur in restaurants and hotels.
The virus is usually mild and lasts for one or two days. Symptoms include vomiting, projectile vomiting, diarrhoea and fever. Most people make a full recovery within a couple of days but it can be dangerous for the very young and elderly people.
For more information please see Public Health England's 'Stop Norovirus spreading this winter' leaflet.
Colds and flu affect over 15 million people a year in the UK and during a pandemic, such as the Swine Flu (H1N1) outbreaks in 2009 and 2010, the symptoms and risks intensify; especially among vulnerable groups such as the young, elderly and those with existing medical conditions.
During 2009 alone, 242 deaths in the UK were directly caused by Swine Flu.
During a health pandemic, the NHS will offer guidance and advice to the public and these can be located on the NHS guidance website.
Flu outbreaks and health pandemics can also affect businesses if several staff are all taken ill and off work at the same time. For more information see the Cabinet Office's Pandemic Flu Checklist for Businesses.