The CDC is Watching for Human Avian Influenza Infections

So far, North America has been lucky. Community acquired infections of avian  influenza have not yet occurred, although an imported case of H5N1 was identified in Alberta Canada in 2013 and two imported cases of H7N9, a husband and wife, were reported from British Columbia in just this past week.

Because of recent outbreak of highly pathogenic avian influenza (H5 subtypes) in wild birds and domestic flocks in North America, the Center for Disease Control has issues guidance for health care workers for identifying and testing patients with potential avian influenza infections. As of January 31, 2015, no H5 subtype human avian influenza infections have been recorded from these outbreaks which have been reported from six western states along the Pacific Flyway (Washington, Oregon, Idaho, Nevada, Utah, and California ). (link)

CDC document: Interim Guidance on Testing, Specimen Collection, and Processing for Patients with Suspected Infection with Novel Influenza A Viruses with the Potential to Cause Severe Disease in Humans

The CDC guidance will help health care workers to assess patients with influenza symptoms that might be at infected with an H5 subtype of avian influenza.   The CDC identifies the following  items as risk factors for potential avian influenza infections. Individuals

who have had recent contact (<10 days prior to illness onset) with sick or dead birds in any of the following categories:

Domestic poultry (e.g., chickens, turkeys, ducks)

Wild aquatic birds (e.g., ducks, geese, swans)

Captive birds of prey (e.g., falcons) that have had contact with wild aquatic bird

Contact may include: direct contact with birds (e.g., handling, slaughtering, defeathering, butchering, preparation for consumption); or direct contact with surfaces contaminated with feces or bird parts (carcasses, internal organs, etc.); or prolonged exposure to birds in a confined space.

The CDC also states that exposures that occur in geographic regions in the United States where newly detected avian influenza A H5 viruses have been identified are of most concern ( e.g. Washington, Oregon, Idaho, Nevada, Utah, and California).

Health care workers need to be familiar with this CDC guidance in order to adequately assess patients who might be infected with avian influenza. Last year a suspected Ebola patient was not correctly diagnosed and was sent home causing an Ebola scare in Texas. The patient later died.  Human infections from H5 subtypes are virulent often resulting death. There is some evidence that H5 subtypes can be transmitted from human-to-human, so early detection is important.

If you experience influenza symptoms and meet any of the risk factors for avian influenza be sure to mention it to your doctor or health care professional at the time of your visit.

Comparing WHO and CDC Projections of Ebola Cases in the Future

Through October  12, 2014, the World Health Organization  (WHO) has reported more than  8900 cases of Ebola since this epidemic began  (link).  The outbreak is currently out of control in three countries in West Africa, Guinea, Liberia, and Sierra Leone.  The graph below depicts the timeline of the growth of the  cumulative number of total cases reported by  each of these countries.  

 

The overall cumulative Ebola case total time series can be fitted to an exponential growth curve to project the total number of cases going into the future. The WHO data indicate that by January  2015 there will be almost 45,000 Ebola cases as shown in the graph below.

 

There is no doubt now that this outbreak will not be contained in West Africa by the end of December.  How many future cases of Ebola will there be is difficult to predict. WHO has noted on several occasions that the officially reported numbers under represent the actual number of cases and deaths in these countries.

On the other hand,  The US Center for Disease Control  (CDC) has projected cases counts ranging from 550,000 to 1.4 million cases in Sierra Leone and Liberia by mid January 2015 (link).  The CDC adjusted  existing case counts by a factor of 2.5 according to their model (as of August 28, 2014).  The graph below compares the differential growth rates based on current WHO data and the estimated case count by the CDC.  According to the CDC estimates, there are now at least 22,000 Ebola cases in West Africa compared to the 8900 reported by WHO.

The graph indicates the clear disparity in the different estimates by these two health agencies of the future case count of Ebola.  As we edge closer to the end of 2014 we will have a better idea of which projection is more accurate.

Ebola infections continue to grow in West Africa

The Ebola epidemic in the three West African countries of Guinea, Liberia, and Sierra Leone continues to grow. As depicted in the graph below,  there have been erratic increases in the number of new Ebola cases in these counties since week number 20 (starting May 11, 2014).

The next graph below, based on the average number of new Ebola cases per week, indicates that the longer term statistical trend in the number of cases is continued exponential increase. The variability in case data from these three countries for week numbers 37 and 38 suggests that local public health officials in these countries can no longer accurately track and count Ebola cases.  Without international support there is no reason to expect that the infection rate will decline any time soon in these countries.

Graph notes: The data used in this graph are derived from World Health Organization and are current through September 16, 2014.  Only cases from the Ebola outbreak in Guinea, Liberia, and Sierra Leone are used in this graph.