The limitations of current diagnostics and public health systems

By Mike Catchpole, Director of the Centre for Infectious Disease Surveillance and Control, Public Health England 

Once thought to be a medical problem of the past, infectious diseases continue to be a major global cause of death and disability, and remain a significant cause of morbidity, mortality and costs to the healthcare system in the UK. The pattern of infectious disease threats that we face changes with time, largely driven by changes in demographics, lifestyle, international trade and travel, and healthcare technology.

Many childhood infections of the past, such as measles and whooping cough are now rare, and polio almost eliminated, in this country as a result of the introduction of highly effective and safe vaccines. However, other diseases of the past, like tuberculosis, have made a resurgence.

We have also seen new infections emerge and even new forms of ‘old’ infections, like the influenza virus. Antibiotic resistant forms of bacteria such as Staphylococcus pose an ever-present threat.

Surveillance is the cornerstone of the prevention and control of infectious diseases, providing the information needed to guide action and evaluate the effectiveness of treatments. The challenge for infectious disease surveillance is to detect serious infections and the early stages of outbreaks in sufficient time to be able to prevent further spread.

The dramatic increase in levels of international trade and travel now means that a new form of infection that arises in one part of the world can be transported to the other side of the globe within a matter of days, or even hours, There is also the possibility of someone being exposed to viruses such as those that cause SARS or lassa fever while in Asia or Africa, and yet not develop symptoms or pose a risk of transmission to others until after they have stepped off the plane in Europe. So early detection is a challenge.

First developed in the late 19th and early 20th century, traditional laboratory techniques to detect infections, can take many hours or even days to provide a definitive answer on the cause of an infection. By the time an outbreak is detected it is often too late as further spread may well have occurred.

New diagnostic technologies could allow earlier and more precise identification (or “finger-printing”) of organisms to be made through molecular or genomic tests. These tests can be carried out in the doctor’s surgery or ‘in the field’ as part of an outbreak investigation, providing real opportunities to identify threats at a much earlier stage.  We could really get ahead of the curve of an impending outbreak or epidemic.

Similarly, new information technologies, such as mobile phones and social media, provide exciting new ways of detecting and tracking illness, even before a patient makes the decision to see a doctor. This offers further opportunities to detect outbreaks and epidemics in real-time; a long time goal of epidemiologists responsible for the control and prevention of infectious disease