Illustration of a woman coughing and spreading an illness

Out of control?

Influenza epidemics are almost impossible to contain; the priority quickly becomes minimising their impact

Stopping an epidemic before it becomes established can save many lives. That was achieved with SARS (just) and is the goal of avian flu control, but was not possible with H1N1 swine flu.

Initial containment calls for highly effective surveillance so that a new outbreak can be identified as rapidly as possible. Isolation measures can then be taken to contain infection and prevent the escape of the virus. Mass culling of birds in the Hong Kong poultry markets helped to contain early bird flu outbreaks. Additional surveillance systems have been put in place to monitor for H5N1 or other bird flu outbreaks.

So why did influenza A(H1N1)pdm09 slip beneath the radar? Important factors include patchy monitoring of influenza in pigs and the mildness of the illness in most people. The pandemic virus was readily transmitted between people, so once it was in the human population it spread rapidly. Even if a case of bird flu in humans is not picked up, because the virus is not transmitted between people it will not spread more widely.

Within individual countries, health policy in response to a possible flu pandemic generally starts with containment: identifying and isolating cases, tracing contacts and treating those infected with antivirals. More general hygiene measures are encouraged. People with known infections are encouraged not to mix and affected schools may be shut.

Some countries might monitor visitors for signs of fever, but this is likely to have little effect other than to delay an epidemic slightly.

Once cases become widespread, containment becomes impractical, and policy shifts to a mitigation phase: trying to minimise the impact of an epidemic. This may mean special protection for the vulnerable and preparing for expected waves of new cases. At this point special measures are likely to kick in, as health services implement pandemic plans. For example, nonessential surgery may be put on hold.

Other public health measures might also be considered, but much depends on the severity of the infection. Closing schools or banning large gatherings (such as football matches or concerts) would be difficult, disruptive and potentially economically costly. If a particularly virulent form of flu appeared, however, such measures might be taken to protect public health.

Lead image:

A woman coughing while entering a lift with five other people inside it, from a Ministry of Health poster, which says ‘Coughs and sneezes spread diseases’.

Wellcome Library, London CC BY


Questions for discussion

  • What would you do to control a flu pandemic?

About this resource

This resource was first published in ‘Influenza special issue’ in October 2009 and reviewed and updated in January 2015.

Microbiology, Ecology and environment, Health, infection and disease
Influenza special issue
Education levels:
16–19, Continuing professional development