WHO Report: 4,735 dead of swine flu

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http://www.who.int/csr/don/2009_10_16/en/index.html

Pandemic (H1N1) 2009 - update 70

Weekly update

As of 11 October 2009, worldwide there have been more than 399232 laboratory

confirmed cases of pandemic influenza H1N1 2009 and over 4735 deaths reported to

WHO.

As many countries have stopped counting individual cases, particularly of milder

illness, the case count is significantly lower than the actually number of cases

that have occurred. WHO is actively monitoring the progress of the pandemic

through frequent consultations with the WHO Regional Offices and member states

and through monitoring of multiple sources of data.

Influenza activity continues to increase in the northern temperate zones across

the world. In North America, the United States is now experiencing nationwide

rates of Influenza-Like Illness (ILI) well above seasonal baseline rates with

high rates of pandemic H1N1 2009 virus detections in clinical laboratory

specimens. Canada is reporting increases in ILI rates for the third straight

week with some provinces now crossing the baseline. Mexico also reports high

intensity and active transmission in some areas of the country. Western Europe

and northern Asia are experiencing increased rates of ILI, well above baseline

in some countries but activity is generally not as widespread as in North

America. Of note, nearly half of the influenza viruses detected in China are

seasonal influenza A (H3N2) viruses, which appeared prior to and is

co-circulating with pandemic H1N1 2009 virus.

The tropical zones continue to have transmission that is mixed as some countries

have now peaked and are declining, while others are experiencing increases. In

the tropical region of the Americas, several Caribbean Island nations are now

reporting increased rates of illness while Brazil, Costa Rica and other

countries on the continent are declining. In South Asia, most countries now

report a decline in rates of illness.

Influenza rates in the temperate zones of the Southern Hemisphere have all

returned to below baseline levels and very few detections of pandemic H1N1 2009

virus are being reported.

Three articles of interest published this week in the peer reviewed literature

reported three different series of seriously ill pandemic influenza patients in

Canada, Mexico, Australia, and New Zealand. Several important observations were

made including:

• A significant portion of patients with severe disease requiring intensive care

had no predisposing conditions. The numbers are not directly comparable as the

studies categorized conditions differently but nearly 1/3 of ICU patients in

Australia and New Zealand had no predisposing conditions. 98% of ICU cases in

Canada had a comorbid condition, which in this report included hypertension,

smoking, and substance abuse, but only 30% had comorbid conditions that were

considered " major " . In Mexico, 84% of critical patients had an underlying

condition, which in the report included hypertension, ever having smoked, and

hyperlipidemia, conditions that are not considered risk factors for severe

influenza outcomes. All three groups were impressed by the number of severe

cases occurring in previously healthy individuals.

• The researchers in Australia and New Zealand reaffirmed that infants under the

age of 1 year have the highest risk of developing severe illness. The average

age of ICU patients was 32, 40, and 44 years in Canada, Australia/New Zealand,

and Mexico respectively.

• The study from Australia and New Zealand estimated that the demand for ICU

beds due to viral pneumonia during the pandemic was as much higher than in

previous influenza seasons. The Canadian study reported that intensive care

capacity in Winnipeg, Manitoba, was " seriously challenged " at the peak of the

outbreak with full occupancy of all regional ICU beds.

All pandemic H1N1 2009 influenza viruses analyzed to date have been

antigenically and genetically similar to A/California/7/2009-like pandemic H1N1

2009 virus.

Systematic surveillance conducted by the Global Influenza Surveillance Network

(GISN), continues to detect sporadic incidents of H1N1 pandemic viruses that

show resistance to the antiviral oseltamivir.