Why is the measles virus so contagious?

An international collaboration involving Inserm has revealed how the measles virus leaves the body of an infected person to contaminate another individual. The researchers have identified a key receptor, located in the trachea, which allows the virus to spread through the air rapidly from one organism to another. The receptor, nectine-4, is also known to be a biomarker for some cancers.

This research appeared in a letter, dated 2 November 2011, published in Nature.

The measles virus is one of the most highly contagious human pathogens and can cause serious, sometimes fatal, complications. It is mainly transmitted when an infected person coughs or sneezes, sending droplets through the air to another individual. This explains why the virus spreads so rapidly through at-risk populations (i.e. persons who are not vaccinated or improperly vaccinated), obstructing world vaccination programmes that seek to eradicate it. Every year, this virus infects more than 10 million children and causes 120,000 deaths in the world. France also faces a measles epidemic that is giving cause for concern. While only forty or so cases were reported in 2006 and 2007, numbers have risen sharply since 2008 (14,600 cases have already been reported since the beginning of 2011) .

The discovery published in the journal Nature explains why this virus spreads so quickly. Viruses generally use cell receptors to initiate and spread the infection throughout the organism. This is the case of the measles virus, which infects the immune cells in the lungs to enter and spread through the body. For the first time ever, this study shows how the measles virus uses another receptor (nectine-4) to 'leave' its host. Nectine-4 is located specifically in the trachea, a part of the anatomy that is 'ideally' suited to airborne contagion.

Nectine-4 is a biomarker for certain types of cancer, including breast, ovarian and lung cancer. Treatments based on the use of a modified vaccine strain of the measles virus are currently being developed for use against some cancers. This virus replicates preferentially in cancer cells, leading to their destruction. The presence of this biomarker in tumours must be taken into consideration to improve the efficacy of these novel therapeutic methods.