Recent spread of avian influenza A (H5N1) virus to poultry and wild birds has increased the threat of human infections with H5N1 virus worldwide. Despite international agreement to stockpile antivirals, evidence-based guidelines for their use do not exist. WHO assembled an international multidisciplinary panel to develop rapid advice for the pharmacological management of human H5N1 virus infection in the current pandemic alert period. A transparent methodological guideline process on the basis of the Grading Recommendations, Assessment, Development and Evaluation (GRADE) approach was used to develop evidence-based guidelines. Our development of specific recommendations for treatment and chemoprophylaxis of sporadic H5N1 infection resulted from the benefits, harms, burden, and cost of interventions in several patient and exposure groups. Overall, the quality of the underlying evidence for all recommendations was rated as very low because it was based on small case series of H5N1 patients, on extrapolation from preclinical studies, and high quality studies of seasonal influenza. A strong recommendation to treat H5N1 patients with oseltamivir was made in part because of the severity of the disease. Similarly, strong recommendations were made to use neuraminidase inhibitors as chemoprophylaxis in high-risk exposure populations. Emergence of other novel influenza A viral subtypes with pandemic potential, or changes in the pathogenicity of H5N1 virus strains, will require an update of these guidelines and WHO will be monitoring this closely.

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The voltage-dependent inhibition of single N-type Ca(2+) channels by noradrenaline (NA) and the delta-opioid agonist D-Pen(2)-D-Pen (5)-enkephalin (DPDPE) was investigated in cell-attached patches of human neuroblastoma IMR32 cells with 100 mM Ba(2+) and 5 microM nifedipine to block L-type channels. In 70% of patches, addition of 20 microM NA + 1 microM DPDPE delayed markedly the first channel openings, causing a four- to fivefold increase of the first latency at +20 mV. The two agonists or NA alone decreased also by 35% the open probability (P(o)), prolonged partially the mean closed time, and increased the number of null sweeps. In contrast, NA + DPDPE had little action on the single-channel conductance (19 versus 19.2 pS) and minor effects on the mean open time. Similarly to macroscopic Ba(2+) currents, the ensemble currents were fast activating at control but slowly activating and depressed with the two agonists. Inhibition of single N-type channels was effectively removed (facilitated) by short and large depolarizations. Facilitatory pre-pulses increased P(o) significantly and decreased fourfold the first latency. Ensemble currents were small and slowly activating before pre-pulses and became threefold larger and fast decaying after facilitation. Our data suggest that slowdown of Ca(2+) channel activation by transmitters is mostly due to delayed transitions from a modified to a normal (facilitated) gating mode. This single-channel gating modulation could be well simulated by a Monte Carlo method using previously proposed kinetic models predicting marked prolongation of first channel openings.

SUMMARY1. Whole-cell currents through low-voltage-activated (LVA) Ca2+ channels carried by monovalent cations were studied in chick dorsal root ganglion (DRG) cells.2. With 120 mm [Na+] on both sides of the membrane and [Ca2"]0 < 100 pSM, the currents reversed at 0 mV. Their half-times of activation and inactivation were strictly voltage-dependent and decreased to near-constant values of 0-6-0 85 and 40 ms, respectively, at positive membrane potentials. The longer activation times were observed with [Ca2+]0 t 50 fM. 3. The selectivity of the Ca21 channel for monovalent ions with reference to internal Na+ was evaluated from the reversal potential. The Li' and Na+ permeabilities were similar. The permeability ratios of K+ and Rb+ were 0-45, and 0-33 for Cs+.4. Micromolar increases in [Ca2+]. produced small voltage shifts of half-times of activation (< + 3 mV at 10 /LM and + 10 mV at 500 ,lM), but strongly depressed the Na+ current. The Ca2+-induced block of Na+ current satisfied a 1: 1 stoichiometry with an apparent KD of 1-8 /tM at -20 mV. The block was, however, relieved with more positive and negative potentials, with KDS of 55 and 8-5 9. The voltage dependence of the Na+ current block by Ca21 ions is best accounted for by a single, centrally located Ca2" binding site. The kinetic features of block and unblock suggest ion-specific but concentration-independent transitions between channel conformations with different ionic selectivities. A state model based on these assumptions was able to reproduce the observed voltage-and concentrationdependent behaviour of the channel.

Emerging health problems require rapid advice. We describe the development and pilot testing of a systematic, transparent approach used by the World Health Organization (WHO) to develop rapid advice guidelines in response to requests from member states confronted with uncertainty about the pharmacological management of avian influenza A (H5N1) virus infection. We first searched for systematic reviews of randomized trials of treatment and prevention of seasonal influenza and for non-trial evidence on H5N1 infection, including case reports and animal and in vitro studies. A panel of clinical experts, clinicians with experience in treating patients with H5N1, influenza researchers, and methodologists was convened for a two-day meeting. Panel members reviewed the evidence prior to the meeting and agreed on the process. It took one month to put together a team to prepare the evidence profiles (i.e., summaries of the evidence on important clinical and policy questions), and it took the team only five weeks to prepare and revise the evidence profiles and to prepare draft guidelines prior to the panel meeting. A draft manuscript for publication was prepared within 10 days following the panel meeting. Strengths of the process include its transparency and the short amount of time used to prepare these WHO guidelines. The process could be improved by shortening the time required to commission evidence profiles. Further development is needed to facilitate stakeholder involvement, and evaluate and ensure the guideline's usefulness.