Swine flu: early hospitalisations

On May 22 2009, the Centre for Disease Control (CDC) published its weekly report in which it discussed the characteristics of the first 30 patients with swine flu who had been hospitalised up to May 17 in California.

This report provides a helpful snapshot of the nature of the illness in a sample of patients hospitalised with swine flu.

Key points

• The majority of the 30 swine flu patients hospitalised in California up to May 17 were discharged after 30 days.
• Those who experienced severe disease and prolonged hospitalisation commonly had underlying conditions that were probably contributing to the severity of their illness.
• The CDC says that more information is needed on which populations are at greatest risk of hospitalisation.

Where was the article published?

This is a Morbidity and Mortality Weekly Report (MMWR) published by the CDC in Atlanta on May 22 2009. These reports are prepared each week based on provisional data from state health departments in the US and are published for doctors, public health practitioners, epidemiologists, nurses and other interested parties.

What kind of study was this?

In this particular report, the CDC discusses the features of the 30 swine flu patients that had been hospitalised in California as of May 17 2009. At this time, there were 553 cases of novel H1N1 influenza reported across California and no fatalities. Of these 553 cases, 333 were confirmed cases, with the remaining 220 being ‘probable cases’ (diagnosed with influenza type A, but waiting for confirmation on whether it was type H1 or H3).

The report summarises the characteristics of these 30 patients and describes four of them in detail. The four case studies illustrate ‘the spectrum of illness severity and underlying risk factors’.

What does the research say?

These are the notable characteristics of the 30 hospitalised patients:

• Twenty-six of the hospitalised cases were confirmed H1N1 infections; four were ‘probable H1N1’.
• Patient ages ranged from 27 days old to 89 years, with an average age of 27.5 years.
• Females outnumbered males and comprised 70% of the cases.
• No patients reported that they had been exposed to pigs or to a known confirmed case of influenza H1N1; four patients had travelled to Mexico in the week before they experienced symptoms.
• Patients were most commonly admitted to hospital with pneumonia and dehydration.
• Nineteen of the cases had underlying medical conditions, of which the most common were chronic lung disease (asthma, COPD), heart disease, obesity, diabetes or conditions that might cause immunosuppression.
• Fever, cough, vomiting and shortness of breath were the most common presenting symptoms and on examination, 15 patients had probable pneumonia.
• Five of the patients were pregnant; two of whom developed complications, one with spontaneous abortion at 13-weeks gestation and the second with premature rupture of membranes at 35 weeks gestation (the outcome of this pregnancy was not reported).
• Half of the patients were treated with oseltamivir (Tamiflu) and for five of them treatment was given within 48 hours of symptoms developing.
• Six of the hospitalised patients had received seasonal influenza vaccination.
• Those who were discharged by May 17 (23 patients) had stayed in hospital for an average of four days (ranging from one to ten days). Those still in hospital on May 17 had stayed an average of 15 days (ranging from four to 167 days). This long hospitalisation was in a five-month-old child, who was born prematurely and had growth retardation, congenital heart disease and lung disease.

Detailed case reports

Selected by CDC to demonstrate patient history and the range of severity.

A five-month-old girl born prematurely with several underlying medical problems including congenital heart disease, lung problems and growth retardation who had been hospitalised since her birth. On her 150th day in hospital, she developed a fever, a cough and had evidence of a lung infection when X-rayed. Tests revealed she was infected with the H1N1 virus. It was unclear how she was infected or if she received antivirals and antibiotics. She was still hospitalised by the time this report was written.

A previously healthy 29-year-old woman who was 28-weeks pregnant when she presented with fever, a productive cough and shortness of breath. She was admitted to hospital and received antibiotics but did not receive antivirals. She gradually improved and was discharged after nine days.

An 87-year-old woman with many comorbidities, including diabetes mellitus, high blood pressure, obesity, coronary artery disease and kidney problems, was admitted following presentation at an emergency department after being found unconscious. She had reported fever, cough and weakness prior to her admission. She was admitted with a diagnosis of heart attack, pneumonia, heart failure and presumed sepsis. Further testing revealed lung masses and she tested positive for H1N1. At the time of the report, she remained hospitalised in critical condition.

A 32-year-old man with a history of obstructive sleep apnoea presented with history of fever, chills and a cough. He had an elevated temperature and some evidence of lung infection on X-ray. He was already taking antibiotics for sinusitis. He was admitted and treated with broad-spectrum antibiotics. Initial tests for flu were negative, but he started antiviral treatment on day two in hospital and a repeat test confirmed H1N1 infection. He was discharged after 10 days in hospital.

Hospitalisations in the UK

The July 16th weekly pandemic flu update by the Health Protection Agency reported that 652 swine flu patients have been hospitalised in England since the pandemic began. Of these, the majority (354 cases) were in the 16 to 64 year-old-age group. The highest hospitalisation rate was in the under-fives.

Health Protection Scotland report that a large proportion (40%) of the 44 patients hospitalised to date in Scotland were known to have underlying comorbidities including chronic respiratory disease, diabetes or immunosuppression.

The government has predicted that for every 100 people infected with swine flu, two will require hospitalisation.

What is the implication and importance of this?

The cases described by the CDC’s May 22 report illustrate the range of severity of hospitalised cases. The majority of hospitalised patients are discharged after a short hospital stay. Two of five pregnant women who were admitted had serious complications, but the CDC says it is not clear what role the H1N1 infection played in this.

While this report is from the relatively early stages of the pandemic, it provides some details about the characteristics of hospitalised H1N1 patients. For those who remain hospitalised and need prolonged intensive care, extremes in age and multiple comorbidities may contribute to the severity of their illnesses.