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The bird flu scare

International health experts are closely monitoring the recently discovered new avian influenza A(H7N9) virus which has emerged into a severe, life-threatening infection.

It was reported initially involving three persons on March 29, in Shanghai and Anghui provinces. In less than two months, it has spread to nearby provinces in China, confirmed by specific laboratory tests. As of April 29, there were 126 confirmed H7N9 infections in humans in China, with 24 (19 percent) dying from the infection. Several days ago, the first reported case of the infection has been confirmed in Taiwan, causing some alarm. It spreading to nearby countries, including the Philippines, is no longer remote.

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The virus has not been previously reported in humans. Although the main sources of infection are birds and poultry, a possible limited human-to-human transmission could not be ruled out.

Avian influenza, simply called avian flu or bird flu, is just one of the strains of influenza viruses which have adapted to a specific host, namely birds.  It has a virulent strain or subtype that causes a highly pathogenic avian influenza.
Although various influenza infections usually adapt to a specific host, the adaptation has been shown to be not completely exclusive. Partial or total adaptation to different species, or a multiple-species adaptation, has been reported. There’s a possibility that the current bird flu virus could have this multiple-species adaptation—to both humans and birds.

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Rapidly progressive

The cases reported usually present with flu-like symptoms and respiratory tract infection. The pneumonia, called acute respiratory distress syndrome (ARDS), is rapidly progressive and will soon followed by death.

The Chinese Center for Disease Prevention and Control gave a detailed report of the profile of patients at high risk of acquiring the infection. The median age of patients with confirmed infection is 61 years, with 21 percent of the cases in persons aged 75 years or older. Majority (71 percent of reported cases) are males.

Surprisingly, only four cases have been confirmed among children, who are supposed to have a weaker resistance compared to adults. In fact, one child, who was symptom-free and appeared healthy, had been tested positive for H7N9.

Majority of patients (76 percent)  had at least one other medical problem which could account for their relatively weaker resistance. The most common reason for seeking consultation or hospitalization was severe respiratory illness. Almost everyone required hospitalization, and in those hospitalized, 21 percent died  due to ARDS and failure of vital organs of the body, like the heart and kidneys. Only 5 percent of reported cases had been discharged from the hospital, as of latest report, and are deemed to be already adequately treated or out of danger. Majority are still confined in the hospital and are being closely monitored.

Since this new avian flu is emerging to be a potential international public health concern, all countries are advised to prepare and respond to H7N9 cases reaching them. Doctors and healthcare workers should always have bird flu at the back of their minds for patients who consult them with acute respiratory illness, and history of bird or poultry exposure or recent travel to China or Taiwan. When the clinical suspicion is strong, these patients should be referred to the country’s health departments for isolation measures and confirmatory testing.

Sensitive to anti-flu drugs

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Although the clinical course is characterized by rapid deterioration, the new bird flu virus has been shown in laboratory tests to be sensitive to available anti-flu drugs like oseltamivir and zanamivir. However, studying the virus’ genetic sequence, scientists have also shown a known marker of drug resistance. The experts fear that this suggests that the bird flu virus’ resistance to antiviral drugs can develop quickly during treatment.

Working feverishly on the virus, scientists have also developed a new diagnostic test, which is supposed to be more sensitive. This new test was approved by the Food and Drug Administration, and can be obtained from any recognized National Influenza Centers globally, or from the Influenza Reagent Resource (http://www.influenzareagentresource.org).

Will the currently used flu vaccine work against bird flu? Not likely, the experts say. Hopefully, a H7N9 candidate vaccine virus will soon be developed. Of course, it’s something that can’t be developed overnight. Realistically, it would still take several months before a vaccination program could be made available. Not to worry at this point since the rate of spread of bird flu cases is not that alarmingly fast. This provides an opportunity for health authorities to review their preparedness programs. Administrative and logistical readiness for a potential influenza pandemic has to be ensured.

It’s better to be prepared than to be sorry.

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TAGS: Bird flu, Health, MD, Medical Files, Rafael Castillo
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