12 May 2009The United Nations World Health Organization (WHO) said today it will soon publish initial guidance for clinical management of influenza A(H1N1) infection, 5,251 cases of which have now been officially reported by 30 countries. The United Nations World Health Organization (WHO) said today it will soon publish initial guidance for clinical management of influenza A(H1N1) infection, 5,251 cases of which have now been officially reported by 30 countries. “This guidance is to help doctors, nurses and persons who will be, and already are, caring for patients with this disease,” Dr. Nikki Shindo, Medical Officer in WHO’s Global Influenza Programme, told reporters in Geneva. At the same time, she highlighted the fact that most patients will not require hospitalization or antiviral therapy. According to the latest figures, Mexico has reported 2,059 laboratory confirmed human cases of infection, including 56 deaths, while the United States has reported 2,600 cases, including three deaths. Meanwhile, Canada has reported 330 cases, with one death, and Costa Rica has reported eight cases, including one death. Another 26 countries have reported laboratory confirmed cases with no deaths.Dr. Shindo said her team has been looking closely into the clinical picture of the disease, including symptoms, severity and factors for hospitalization and treatment, since the new flu outbreak began. It has been working closely with Mexican and US health officials and partners on the ground, and has seen a spectrum of the virus from mild – involving typical flu symptoms – to a very severe form of the disease, which includes pneumonia and sometimes requires mechanical ventilation. “The most important question from the beginning was why only Mexico was having very severe cases,” she stated. “The proportion of severe cases initially seemed to be very high in Mexico but not in the other countries. But as more information became available, the proportion of mild versus severe became very similar between these two countries – United States and Mexico.”Dr. Shindo said that there are mainly two groups that have been affected by very severe illness in these two countries. The first is persons with underlying chronic medical conditions, such as weak immune system, diabetes, cardiovascular disease and asthma. There have also been reports of very severe illness and death in pregnant women. The second group is previously healthy, very fit young children and adults, and the reason why these cases become very severe is yet unknown, she said, adding that WHO is working with clinicians, especially from Mexico, to find the reason.