31 August 2009

WHO offe= rs lessons for the upcoming second wave of pandemic H1N1 Influenza virus

On Friday, August= 28, the World Health Organization (WHO) posted online a succinct discussion regarding the pandemic influenza H1N1/2009 situation titled “Preparing for the second wave: lessons from current outbreaks”. The full document appears at: www.who.int/csr/disease/swineflu/notes/h1n1_second_wave= _20090828/en/index.html. The three-page WHO document is divided into nine (9) subheadings:

1) H1N1 now t= he dominant strain

2) Large populations susceptible to infection

3) Monitoring= for drug resistance

4) Not the sa= me as seasonal influenza

5) Severe respiratory failure

6) Vulnerable groups

7) Higher ris= k of hospitalization and death

8) Implicatio= ns for the developing world

9) Co-infecti= on with HIV

Several points of emphasis include:

a. Globally, = the new pandemic virus has become the predominant strain of influenza in the southern hemisphere’s now concluding winter season, as well as the northern hemisphere’s concluding summer. Unlike seasonal flu, this vi= rus has continued to be transmitted in the temperate regions of the northern hemisphere during the summer (including the USA, Mexico, and Canada). Fortunately, so far, no significant mutations or recombination events have occurred that increased the virulence of this new virus.<= /p>

b. “Large numbers of severely ill patients requiring intensive care are likely to be the most urgent burden on health services, creating pressures that could overwhelm intensive care uni= ts and possibly disrupt the provision of care for other diseases.” (bold type added).

c. “To = date, most severe cases and deaths have occurred in adults under the age of 50 ye= ars, with deaths in the elderly comparatively rare.”

d. “Per= haps most significantly, clinicians from around the world are reporting a very severe form of disease, also in young and otherwise healthy people, which is rarely seen during seasonal influenza infections. In these patients, the vi= rus directly infects the lungs, causing severe respiratory failure…During= the winter season in the southern hemisphere, several countries have viewed the need for intensive care as the greatest burden on health services. Some cities in these countries report that nearly 15 perce= nt of hospitalized cases have required intensive care. Preparedness measures n= eed to anticipate this increased demand on intensive care units, which could be overwhelmed by a sudden surge in the number of severe cases”.

e. Asthma and diabetes are risk factors for more severe pandemic H1N1 flu disease. “= ;WHO estimates that, worldwide, more than 230 million people suffer from asthma,= and more than 220 million have diabetes”.

f. Referring = to these and other risk factors for severe pandemic H1N1 flu virus disease, WHO emphasized that “such findings are likely to have growing relevance as the pandemic gains ground in the developing world, where many millions of people live under deprived conditions and have multiple health problems, wi= th little access to basic health care. As much current data about the pandemic comes from wealthy and middle-income countries, the situation in developing= countries will need to be very closely watched. The same virus that causes manageable disruption in affluent countries could have a devastating impact in many pa= rts of the developing world.” (bold type added)= .

g. “Ear= ly data from two countries suggest that people co-infected with H1N1 and HIV <= span class=3DGramE>are not at increased risk of severe or fatal illness, provided these patients are receiving antiretroviral therapy.”

Soon the pandemic H1N1/2009 influenza virus will return for its second wave in the northern hemisphere. At the same time it quite possibly will continue to be transmit= ted in the tropical regions and in the southern hemisphere, albeit at a slower = rate than during the past three months of winter there. Thus, these WHO “lessonsR= 21; and observations are timely. =

A crucial point is the limited data from developing nations, and that “much current data about the pandemic comes from wealthy and middle income countries”. At this point, therefore, we do not really have a robust or sufficient understanding of what this virus has done, and is likely to do, in the comi= ng six months in many of the developing nations where so much of the global population lives. =

This is the same large part of the global population that will have the least, if any, acces= s to pandemic H1N1 influenza vaccine and effective antiviral drugs and intensive care.

For these reasons, along with being more vulnerable to severe pandemic flu disease due to underlying respiratory diseases, diabetes, and other such risk factors, act= ual mortality figures will highest in such nations. Clearly, it bears remembering that insufficient measurement of such mortality does not mean that it does not o= ccur and might not be at least partially mitigated.

Daniel R. Lucey, MD, MPH

EROne Institutes, Department of Emergency Medicine<= /o:p>

Washingt= on Hospital Center

Adjunct Professor Microbiology and Immunology=

Georgeto= wn University Medical Center, Washington DC

Website for this posting: www.BePast.org (requires IE= )