The existing stockpiles of antivirals are nowhere near adequate to cope with a pandemic. Are these essential drugs? Anybody planning to write a review about anti-influenza drugs for the 2005 WHO
Essential Drugs List of these drugs? Copied as fair use from the Lancet Infectious Diseases.
http://infection.thelancet.com/journal/vol4/iss10/full/laid.4.10.the_lea... _edge.30755.1 Avian influenza refuses to go away.
The outbreak of highly pathogenic influenza A H5N1 was first reported in poultry in South Korea in December of last year, and subsequently spread to another seven Asian countries. After a quiet period in the second quarter of this year, the ProMed wires have been buzzing since July with news of outbreaks of the virus in poultry in China, Thailand, Vietnam, Indonesia, and Malaysia.
Fortunately, only Thailand and Vietnam have reported human cases (13 cases with nine deaths, and 27 cases with 20 deaths, respectively, as of September 10), indicating that the virus transmits poorly from birds to people. Reports from China that H5N1 is widespread in domestic ducks and wild
birds suggest that the virus is deeply entrenched in the environment and may be impossible to eliminate.
Experimental infection of cats with H5N1 indicates that these animals could serve as a transmission bridge between poultry farms or between poultry and people. Perhaps we should not give too much weight to disease produced in the laboratory, but cats should be studied in future epidemiological investigations of H5N1 transmission.
Of more importance potentially was the announcement, made on August 20 by a researcher from China's Harbin Veterinary Research Institute, that H5N1 has been isolated from pigs on farms in various parts of China. Pigs can also be infected with human influenza A viruses, such as H3N2. The co-circulation of influenza viruses of avian, human, and pig origin in pigs might lead to genetic eassortment between the viruses, and, in the worse-case scenario, emergence of a new pandemic influenza strain.
It has since emerged that H5N1 was isolated once from material collected from pigs in Fujian province in 2001, and that of 1936 samples collected from pigs in 14 Chinese provinces in 2003 only one was positive for H5N1, also from Fujian. A further survey involving 4447 samples from pigs in ten
provinces, including Fujian, done between April and August this year revealed no cases of H5N1 infection.
Moreover, testing earlier this year for H5N1 in pigs on Vietnamese farms where the disease was rife among poultry, found no evidence of infection. And during regular testing in Hong Kong of pigs imported from mainland China, no H5 avian influenza subtype has been isolated. So the implications for human health of the discovery of H5N1 in pigs in China remain unclear.
Nevertheless, there is absolutely no room for complacency in the international response to, what now seems to be endemic, highly pathogenic avian influenza. The great fear is that avian disease will give rise to a human influenza pandemic. Of the three prerequisites for a human pandemic, two have been met: emergence of a new influenza virus to which the population has little or no immunity and against which there is no effective vaccine and ability of the virus to replicate in human beings
and cause disease.
As yet, there is no evidence of the third prerequisite efficient human-to-human transmission being met. There has not been an influenza pandemic since 1968 (so called Hong Kongflu). However, sources within WHO believe that we are as close to the next pandemic as we have been at any time in the past 36 years, with all the necessary ingredients currently mixing in Asia. Epidemiological modelling
suggests that a future influenza pandemic will cause 2774 million deaths worldwide.
The severe acute respiratory syndrome outbreak of 2003 merely hinted at the likely economic consequences of pandemic influenza. The WHO pandemic preparedness plan was published in 1999 and is in the process of being revised. Early detection of unusual outbreaks by the WHO network of 112 national influenza centres will be key to containment of potentially pandemic strains.
As Iain Stephenson and colleagues said in this journal in August, vaccination is likely to remain the principal means of combating pandemic influenza (Lancet Infect Dis 2004 4:499509). However, production of a vaccine against the H5N1 strain is complicated by numerous technical, safety, and regulatory considerations. Indeed, it may be 8 months or more into a pandemic before a vaccine is
Antiviral drugs could be used to contain the pandemic and reduce fatalities while vaccine supplies are prepared. H5N1 seems to be resistant to the M2 inhibitors (amantadine and rimantadine) the
neuraminidase inhibitors zanamivir and oseltamivir are effective, although oseltamivir-resistant influenza H3N2 in children treated for the disease was reported recently. What is certain is that existing stockpiles of antivirals are nowhere near adequate to cope with a pandemic.
The threat to human health from pandemic influenza is likely far greater than that from bioterrorism. Responsible governments must be prepared to invest in global preparedness for the next pandemic.  (Source: The Lancet, 13 October 2004)