There is probably no more nebulous disease description than that of `ILI’ or an influenza-like-illness. It ranks up there with `malaise’ and `fatigue’ among the most common of human complaints, and is just about as specific.
Nearly all viral (and a fair number of bacterial, parasitic, and fungal) infections present – at least in their prodromal stage – with flu-like symptoms.
The public tends to categorize mild respiratory infections as `colds’ and more severe illnesses as `the flu’, but doctors know there is a whole galaxy of pathogens out there that can mimic influenza.
Which is why doctors usually refer to `picking up a virus’, or having an ILI (Influenza-like Illness or sometimes ARI Acute Respiratory Infection), when rendering a diagnosis.
Elaborate testing isn’t usually done because of the costs involved, and because knowing the etiology doesn’t really affect treatment. Bed rest, fever reducers, and plenty of fluids is the usual regimen.
Consequently, there are probably still a number of as-yet unidentified respiratory viruses running around out there.
All of which serves as prelude to a report in today’s MMWR on the detection of HEV68 – or Human Enterovirus 68 – that has produced a number of clusters of respiratory illness around the world over the past couple of years.
Enteroviruses encompass a large family of small RNA viruses that include the three Polioviruses, along with myriad non-polio serotypes of Human Rhinovirus, Coxsackievirus, echovirus, and human, porcine, and simian enteroviruses.
The few excerpts from today’s MMWR report (follow the link to read it in its entirety):
Clusters of Acute Respiratory Illness Associated with Human Enterovirus 68 --- Asia, Europe, and United States, 2008--2010
WeeklySeptember 30, 2011 / 60(38);1301-1304
In the past 2 years, CDC has learned of several clusters of respiratory illness associated with human enterovirus 68 (HEV68), including severe disease. HEV68 is a unique enterovirus that shares epidemiologic and biologic features with human rhinoviruses (HRV) (1).
First isolated in California in 1962 from four children with bronchiolitis and pneumonia (2), HEV68 has been reported rarely since that time and the full spectrum of illness that it can cause is unknown. The six clusters of respiratory illness associated with HEV68 described in this report occurred in Asia, Europe, and the United States during 2008--2010.
HEV68 infection was associated with respiratory illness ranging from relatively mild illness that did not require hospitalization to severe illness requiring intensive care and mechanical ventilation. Three cases, two in the Philippines and one in Japan, were fatal. In these six clusters, HEV68 disproportionately occurred among children.
CDC learned of clusters of HEV68 from public health agencies requesting consultation or diagnostic assistance and from reports presented at scientific conferences. In each cluster, HEV68 was diagnosed by reverse transcription--polymerase chain reaction (RT-PCR) testing targeting the 5'-nontranslated region, followed by partial sequencing of the structural protein genes, VP4-VP2, VP1, or both, to give definitive, enterovirus type-specific information.
This report highlights HEV68 as an increasingly recognized cause of respiratory illness. Clinicians should be aware of HEV68 as one of many causes of viral respiratory disease and should report clusters of unexplained respiratory illness to the appropriate public health agency.
Occurrence of human enterovirus 68, by month, duration, and geographic location --- Asia, Europe, and United States, 2008—2010
In recent years, with advances in microbiology and sequence-independent amplification of viral genomes, the ability of scientists to identify new viruses has improved greatly and so they are adding new names to the `suspect list’.
About a decade ago the human metapneumovirus (HMPV) was identified in Dutch children with bronchiolitis. Since then, it has been found to be ubiquitous around the world, and responsible for a significant percentage of childhood respiratory infections . . . yet until 2001, no one knew it existed.
Human Bocavirus-infection (HBoV) wasn’t identified until 2005, when it was detected in 48 (9.1%) of 527 children with gastroenteritis in Spain (cite).
And the list grows longer every year.
While discovered 40 years ago, according to this MMWR report, testing for HEV68 remains problematic. So we probably don’t have a good handle on how common it really is.
The summary provided for this release reads:
What is already known on this topic?
Human enterovirus 68 (HEV68) is a unique enterovirus that shares epidemiologic and biologic features with human rhinoviruses.
What is added by this report?
Although isolated cases of HEV68 have been reported since the virus was described in 1962, clusters of cases have been recognized only recently. The clusters described in this report occurred late in the typical enterovirus season and included severe cases, three of which were fatal.
What are the implications for public health practice?
Clinicians should be aware of HEV68 as one of many possible causes of viral respiratory disease. Some diagnostic tests might not detect HEV68 or might misidentify it as a human rhinovirus.