Clinical descriptions of avian flu in humans offered

Feb 12, 2004 (CIDRAP News) – Fever, cough, and chest radiograph abnormalities were the most common features in preliminary clinical descriptions of 15 human cases of H5N1 avian influenza, provided today by US and World Health Organization (WHO) officials.

The WHO published information on 10 Vietnamese patients, eight of whom died, while the US Centers for Disease Control and Prevention (CDC) reported on five Thai patients, all of whom died.

Also today, the WHO reported two more confirmed human cases of avian influenza, one each in Vietnam and Thailand. A 19-year-old Vietnamese man died of the illness, becoming the country's 19th case and 14th fatality. Thai officials reported their country's sixth case, in a 13-year-old boy.

Clinical descriptions of 10 Vietnamese patients, who ranged from 5 to 24 years old, show that eight had a history of direct contact with poultry, according to the WHO. There was no clear evidence of person-to-person transmission in any of the cases.

The patients' main presenting symptoms were fever greater than 38ºC, dyspnea, and cough. All the patients had significant lymphopenia and chest radiograph abnormalities, including "diffuse, multifocal or patchy infiltrates." None of the patients had a sore throat, conjunctivitis, rash, or runny nose, but 7 of the 10 had diarrhea or loose stools.

Data on six of the Vietnamese cases showed the mean incubation time for the illness was 3 days (range, 2 to 4 days). In the fatal cases, patients died a mean of 10 days after onset of illness. The WHO said a more complete report on the cases has been accepted by The New England Journal of Medicine.

The five Thai patients included four boys aged 6 or 7 years and a 58-year-old woman, the CDC reports in the Feb 13 issue of Morbidity and Mortality Weekly Report. All had been exposed to chickens. Like the Vietnamese patients, the Thai patients all had fever, cough, and abnormal chest radiographs. But the Thai cases differed from the Vietnamese ones in that there were no reports of diarrhea, while four patients had sore throat and two had runny nose.

All of the Thai patients suffered respiratory failure and were intubated a median of 7 days after the onset of illness, according to the report. Three needed support for decreased heart function. None had documented evidence of a secondary bacterial infection. Three patients were treated with oseltamivir late in their illness.

Three of the children died between 2 and 4 weeks after the illness began, while the woman and one child died just 8 days after illness onset, the report says.

The CDC says the Thai cases resemble in some respects the cases of severely affected patients in the H5N1 outbreak in Hong Kong in 1997, even though the 1997 and current viruses differ. The case similarities include the early features of fever, sore throat, cough, and lymphopenia, in addition to pneumonia leading to respiratory failure and death. But the Hong Kong cases included gastrointestinal symptoms, which were not seen in the Thai cases.

Because the current H5N1 virus seems resistant to the antiviral drugs amantadine and rimantadine, the CDC says patients should be treated with neuraminidase inhibitors (such as oseltamivir) early in the illness. However, the effectiveness of antiviral drugs, and at what stage of illness they lose efficacy, are unknown, the report says.

The CDC says clinicians should be aware of the clinical features of the disease. In a separate MMWR report today, the agency presents interim recommendations for evaluation and reporting of suspected cases.

See also:

WHO's Feb 12 update on avian flu
http://www.who.int/csr/don/2004_02_12a/en/

MMWR description of five human H5N1 cases in Thailand
http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5305a2.htm

WHO's summary description of 10 human cases in Vietnam
http://www.who.int/influenza/resources/documents/vietnamclinical/en/index.html

CDC's interim recommendations for evaluation and reporting of suspected cases
http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5305a1.htm

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