Mon, Apr 22, 2013 - Page 8 News List

Rational approach needed for H7N9 threat

By Hsieh Yen-yau 謝炎堯

Modern man emerged about 50,000 years ago. Birds and avian influenza, commonly known as bird flu, have existed on Earth for much longer than humans. It can be deduced from the fact that humans and birds have coexisted for more than 50,000 years that avian influenza does not easily infect humans. Only a small minority of people whose bodies contain cells with rare and special kinds of receptors will become ill from bird flu viruses.

This has been going on for millennia; it is just that in the past people did not have molecular biology technology available with which to diagnose it.

In 1997, the first known cases of humans being infected with H5N1 avian influenza were detected in Hong Kong; 18 people were infected, six of whom died. In 2003, 83 people in the Netherlands were infected by H7N7 bird flu, but only one died. In 2003, 130 people in Southeast Asia were infected by H5N1 bird flu, of whom 68 died.

Sixteen years have passed since the Hong Kong outbreak, with sporadic cases being detected every year. The mortality rate from all these cases stands at 60 percent, but no epidemic of human-to-human transmission has occurred, so nobody in the world has been strongly motivated to manufacture or administer H5N1 avian influenza vaccines.

Only 60 people out of China’s 1.34 billion population had been infected by H7N9 bird flu from the middle of February through April 15, and 13 of those people have died. Therefore, there is no urgent need to hurriedly produce vaccines.

In Europe and the US, the process of obtaining virus strains to manufacturing vaccines takes at least five months. Sterile hen’s eggs, which are in limited supply, have to be carefully selected for purchase, and then many repetitious tests have to be done to distinguish between viral and bacterial infections, to ensure that vaccines are safe.

To start manufacturing vaccines within six to eight weeks would require omitting a lot of steps in testing. In that case, when people were injected with vaccines there could be a repeat of the incident in which an inoculation caused a little boy named Liu to get infected with the B19 parovirus.

Besides, a global pandemic arising form human-to-human transmission can only happen if a new mutant strain of the virus emerges, and we cannot expect that any vaccine produced now would offer protection against such a mutant strain.

Bird flu vaccines have never been subjected to standard human clinical studies to prove that they can protect people from getting sick and dying. The so-called clinical studies that have been done have only been to test the presence and amount of antibodies produced in the body following vaccination. The mere presence of antibodies does not necessarily mean that the vaccination protects patients against the illness. It could be like the Maginot Line built by France to defend against attack from the east, which failed to stop the German invasion in World War II.

When people do get infected by influenza, they may be given a neuraminidase inhibitor such as Tamiflu, but these drugs have no therapeutic effect against secondary pneumonia.

We need to take a rational approach to unpredictable threats. Reasonable steps that can be taken are to strengthen measures to monitor influenza and to control and prevent infection. Physicians should be asked to examine patients carefully to detect cases of secondary pneumonia as early as possible and entrust patients to the care of thoracic and respiratory experts. That is the only way to reduce the mortality rate among all kinds of influenza patients.

This story has been viewed 1428 times.
TOP top