At the risk of sounding like a broken record, we really don’t know the true number of H5N1 (or MERS-CoV, H7N9, et al.) infections around the world. The quality, availability, and consistency of lab testing varies considerably between (and indeed, even within) countries.
Many nations must send samples to a reference lab outside their borders in order to test for exotic viruses.
But over the years we’ve seen a number of `suspected cases’ around the world that were either never tested, or whose negative test results were suspect.
In many places people succumb to diseases without ever seeing the inside of a hospital, much less having lab tests run. Which may - at least partially - explain why some places report H5N1 in poultry, but have yet to report a human case.
Don't test, don't find. Know nothing.
Today we’ve a report out of Nepal (h/t Gert van der Hoek on FluTrackers) – a nation which is currently embroiled in a major outbreak of H5N1 in its poultry - that suggests they may have recently missed two recent H5N1 fatalities.
But since they didn’t test (or even collect samples), we will probably never know. A third case is being tested, and we should have results in a week.
First the report from the Himalayan Times, then I’ll return with more.
No bird-to-human bird flu transmission has been reported so far in Nepal.
NARAYANGADH: Bird flu has been suspected in the deaths of two women, who suffered from common cold and fever, at the Teaching Hospital of College of Medical Sciences in Bharatpur.
The hospital has written a letter to the District Public Health Office (DPHO) after the twin deaths on Saturday, suspecting that the victims were infected with the avian influenza virus (H5N1). However, no sample was collected from the deceased for further laboratory test.
Another patient suffering from common cold, cough and fever is receiving treatment at the ICU of the same hospital. She is given Tamiflu, the antiviral medicine used to treat bird flu.
According to Public Health Inspector Ram K.C., nasal and throat swabs collected from her have been sent to the National Public Health Laboratory in Kathmandu for the confirmation of suspected virus.
It is a bit difficult to understand why samples weren’t collected - even post-mortem - but this story indicates they were not. An opportunity lost.
To be fair - it doesn’t matter where in the world you are, or what disease you are interested in – we really can only guess at its true incidence. Our own CDC can only roughly estimate the number of cases of diseases we have each year.
As the pyramid chart above indicates, only a tiny fraction of infectious disease cases are actually reported to health authorities. - Credit CDC
It was just a week ago, in CDC: Estimate Of Yearly Lyme Disease Diagnoses In The United States, that we learned the true burden of Lyme disease in this country may be as much as 10 times greater than are reported.
And just about 2 months ago, in CID Journal: Estimates Of Human Infection From H3N2v (Jul 2011-Apr 2012), we saw a study that estimated that in 2011 – a year where there were only 12 cases of H3N2v reported – the real number of cases was probably in excess of 2000.
While it is clearly impossible to test everyone for everything, the more testing that we can do, the better will be our understanding of the burden of, and threat posed by, these emerging viruses.
For more on the difficulties in assessing the incidence (and mortality/morbidity rates) of emerging diseases, you may wish to revisit: