Clinical features of severe cases of pandemic influenza ~ WHO

[mzmolly]

More information at the WHO website > WHO.INT

Clinical picture different from seasonal influenza

Participants who have managed such cases agreed that the clinical picture in severe cases is strikingly different from the disease pattern seen during epidemics of seasonal influenza. While people with certain underlying medical conditions, including pregnancy, are known to be at increased risk, many severe cases occur in previously healthy young people. In these patients, predisposing factors that increase the risk of severe illness are not presently understood, though research is under way.

In severe cases, patients generally begin to deteriorate around 3 to 5 days after symptom onset. Deterioration is rapid, with many patients progressing to respiratory failure within 24 hours, requiring immediate admission to an intensive care unit. Upon admission, most patients need immediate respiratory support with mechanical ventilation. However, some patients do not respond well to conventional ventilatory support, further complicating the treatment.

On the positive side, findings presented during the meeting add to a growing body of evidence that prompt treatment with the antiviral drugs, oseltamivir or zanamivir, reduces the severity of illness and improves the chances of survival. These findings strengthen previous WHO recommendations for early treatment with these drugs for patients who meet treatment criteria, even in the absence of a positive confirmatory test.

In addition to pneumonia directly caused by replication of the virus, evidence shows that pneumonia caused by co-infection with bacteria can also contribute to a severe, rapidly progressive illness. Bacteria frequently reported include Streptococcus pneumoniae and Staphylococcus aureus, including methicillin-resistant strains in some cases. As these bacterial co-infections are more frequent than initially recognized, clinicians stressed the need to consider empiric antimicrobial therapy for community acquired pneumonia as an early treatment.

On an up note:

The meeting confirmed that the overwhelming majority of persons worldwide infected with the new H1N1 virus continue to experience uncomplicated influenza-like illness, with full recovery within a week, even without medical treatment.

*edited to repair link*

[HuckleB]

1. K & R. Valuable information!

[mzmolly]

2. Thanks HB.

[mzmolly]

3. Kicking with a highlight: "Groups at greatest risk"

Groups at greatest risk

Participants agreed that the risk of severe or fatal illness is highest in three groups: pregnant women, especially during the third trimester of pregnancy, children younger than 2 years of age, and people with chronic lung disease, including asthma. Neurological disorders can increase the risk of severe disease in children.

Evidence presented during the meeting further shows that disadvantaged populations, such as minority groups and indigenous populations, are disproportionately affected by severe disease. Although the reasons for this heightened risk are not yet fully understood, theories being explored include the greater frequency of co-morbidities, such as diabetes and asthma, often seen in these groups, and lack of access to care.

Although the exact role of obesity is poorly understood at present, obesity and especially morbid obesity have been present in a large portion of severe and fatal cases. Obesity has not been recognized as a risk factor in either past pandemics or seasonal influenza.

~ Recap ~

* PREGNANT WOMAN
* CHILDREN < 2
* PEOPLE WITH CHRONIC LUNG DISEASE
* DIABETICS
* NEUROLOGICAL DISORDERS
* DISADVANTAGED/MINORITY GROUPS
* OBESITY (Possible inflammation is a contributing factor - noted in other articles)

[snagglepuss]

5. This WHO info is puzzling because US demographics are different.

According to US demographics 68% of people who die are between 25 to 68. Any ideas about this discrepancy?

From

http://www.ottawacitizen.com/health/Most+H1N1+hospitali...


Of 4,958 people hospitalized with lab-confirmed H1N1 between Sept. 1 to Oct. 10 in 27 states, 53 per cent were people under 25

...

Thirty-nine per cent of hospitalizations are occurring in people aged 25 to 64; only seven per cent are occurring in the elderly.

...

Normally with seasonal flu, about 60 per cent of hospitalizations occur in people 65 and older.

...

Of 292 H1N1 deaths reported from 28 states since Sept. 1, about 24 per cent involved people under age 25. About 65 per cent of the deaths are in people 25 to 64.

Just 12 per cent of deaths from swine flu since Sept. 1 are occurring in seniors 65 and up.

Normally, 90 per cent of flu fatalities occur in people 65 and older

[mzmolly]

6. Very interesting. I have no idea why we'd have such a discrepancy?

Edited to add this: http://blogs.wsj.com/health/2009/10/09/swine-flu-who-is... /

I wonder if the US has higher obesity rates which contribute to the stat differences?

[mzmolly]

7. More from Medscape: "Severe H1N1 Infection in Children Linked to Asthma and Other Diseases"

http://www.medscape.com/viewarticle/709119

SNIP

One or more underlying medical conditions was found in 66% of the children, with the most common being asthma, sickle cell disease, and encephalopathy. Other underlying conditions were pneumonia and congenital heart disease.

Although most of the children displayed the usual features of H1N1 —fever, cough, and sore throat — a striking number also had gastrointestinal symptoms (49%). In fact, the 1 death that occurred from H1N1 was attributed to gastrointestinal complications, underlying lung disease, and encephalopathy.

Fever was seen in most of the children, and neurological features of the disease were common, with 7 children experiencing febrile seizures. In addition, 35% of the children had oxygen-saturation levels below 95%, and 4 of the sickest patients required mechanical ventilation.

Thirteen of the children (16%) required admission to the ICU, and most of those children had underlying comorbidities. The findings suggest that the infection might be particularly severe in these children, the investigators say. Despite the severity of illness, length of stay in the ICU was brief. Most of the children did not have extended stays in the hospital. The mean hospitalization for the group was 4 days.

The Canadian team noted that some lessons could be drawn from their study. Most children with H1N1, even those who are hospitalized, have moderate disease, they note. However, gastrointestinal symptoms and febrile seizures are prevalent in children with H1N1. Thus, it is important that clinicians pay attention to these symptoms when evaluating children for H1N1 to improve diagnosis and treatment, the researchers advise.

/SNIP

More at the link above.

[snagglepuss]

4. .

[mzmolly]

8. "About 70 percent of people who have been hospitalized with H1N1 ..."

"About 70 percent of people who have been hospitalized with H1N1 flu have had one or more medical conditions..."

http://www.flu.gov/individualfamily/about/h1n1/index.ht...

[mzmolly]

9. "the vast majority of people who have contracted H1N1 have recovered without medical intervention"

http://www.flu.gov/individualfamily/about/h1n1/index.ht...

[mzmolly]

10. "H1N1 can lead quickly to viral pneumonia"

http://www.charlotteobserver.com/408/story/1005530.html

So far, the virus does not seem to sicken or kill people more often than the typical flu. But the pattern of people getting seriously ill is far different than in typical flu seasons. The elderly, who are usually most vulnerable, are generally spared; children, teen-agers, pregnant women and young adults are the most common victims.

Seasonal flu viruses tend to infect primarily the upper respiratory system. But recent animal studies and autopsies on about 100 swine flu victims show that H1N1 infects both the upper respiratory tract, which makes it relatively easy to transmit, and also the lungs, which is more similar to the avian flu virus that has been circulating in Asia.

About a third of patients who required intensive care had bacterial pneumonia, but H1N1's proclivity to infect lung cells makes it more likely than seasonal flu to cause viral pneumonia, which can lead to life-threatening lung damage.

While about two-thirds of U.S. patients who were hospitalized in the spring had other medical conditions, the CDC reported this week that an analysis of more than 1,400 hospitalized victims found perhaps half had no serious health problems.