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Morbidity and Mortality Weekly Report

Introduction and Transmission of 2009 Pandemic Influenza A (H1N1) Virus – Kenya, 2009

Press Contact: CDC, Division of Media Relations
Phone: (404) 639-3286

Investigations into the initial cases of 2009 pandemic influenza A (H1N1) showed that the infectiousness of the pandemic influenza virus may be similar to that of seasonal influenza, but more studies are needed to better understand the infectiousness of the pandemic virus. Only one small retrospective study has reported a 30 percent secondary attack rate for laboratory-confirmed 2009 pandemic influenza A (H1N1) among tourists to China. Investigations into the initial cases of 2009 pandemic influenza A (H1N1) in Kenya during June–July 2009 showed an overall laboratory-confirmed secondary attack rate of 26 percent in households, which is similar to rates reported previously for seasonal influenza. However, additional studies are needed to better understand the secondary attack rates for laboratory confirmed 2009 pandemic influenza A (H1N1) in both traditional and non-traditional household settings.

2. Reduction in Rotavirus After Vaccine Introduction – United States, 2000-2009

Press Contact: CDC, Division of Media Relations
Phone: (404) 639-3286

Rotavirus disease in US children has decreased substantially since the introduction of routine vaccination of US infants against rotavirus. Worldwide, rotavirus is the leading cause of severe acute diarrhea in children aged <5 years. In the United States, before introduction of a rotavirus vaccine in 2006, rotavirus caused an estimated 20-60 deaths, 55,000-70,000 hospitalizations, 205,000-272,000 emergency department visits, and 410,000 outpatient visits annually in children <5 years of age. CDC analyzed data from a national network of sentinel laboratories which showed that the 2007-08 and 2008-09 seasons were both shorter and later than during pre-vaccine seasons in 2000-2006. Although the 2008-09 season had slightly more positive rotavirus test results than in 2007-08, the number of positive test results for both seasons was substantially lower than during 2000-2006. Cases of rotavirus disease have decreased since introduction of rotavirus vaccination, but continued surveillance is needed to better characterize the impact of rotavirus vaccine.


3. Progress Toward Poliomyelitis Eradication – Nigeria, January 2008-July 2009

Press Contact: CDC, Division of Media Relations
Phone: (404) 639-3286

Despite increasing commitment by the government of Nigeria to eliminating wild poliovirus transmission and some indicators of progress, all three types of poliovirus are still being transmitted and resulting in paralytic disease among children; continued sustained commitment to polio eradication activities is essential at national, state, and local levels in Nigeria. Nigeria had the world’s highest burden of wild poliovirus (WPV) in 2008, with 798 (48 percent) of the 1651 cases reported globally. During 2008-2009, Nigeria was the source of transmission of poliovirus to thirteen neighboring countries. With increased activities to interrupt WPV transmission during 2008, the number of type 1 WPV dropped substantially in the first seven months of 2009, as did the proportion of children who were reported to have never received oral polio vaccine; however, type 3 WPV cases rose, and vaccine-derived poliovirus cases also increased. With increased commitment of religious, traditional, and community leaders, as well as increased political oversight of polio vaccination activities with better implementation, more children will be protected against all three types of WPV in Nigeria.




  • Historical Document: October 22, 2009
  • Content source: Office of Enterprise Communication
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