Synopsis for December 16, 2005

The MMWR is embargoed until Thursday, 12 PM EST.

1. West Nile Virus Activity – United States, January 1 – December 1, 2005
2. Respiratory Syncytial Virus Activity – United States, 2004 - 2005

West Nile Virus Activity – United States, January 1 – December 1, 2005

An increase in WNV cases in 2005 compared with 2004 signals that WNV activity in the United States will continue for the foreseeable future. Ongoing WNV surveillance is necessary to monitor the spread of the virus and target prevention and control strategies including community-level mosquito control, and promotion of personal protection against mosquito bites such as use of repellents and avoiding outdoor exposure when mosquitoes are avidly feeding.

West Nile virus (WNV) is the leading cause of mosquito-borne encephalitis in the United States. Since its detection in 1999 in New York, WNV has caused seasonal epidemics of febrile illness and severe neurologic disease across the United States. During 2005, a provisional total of 2,744 cases of WNV disease in humans were reported in the United States, an increase from 2,359 during the same period in 2004; 1,165 cases were neurologic disease including meningitis, encephalitis or acute flaccid paralysis. This report summarizes the epidemiology of WNV from January 1 through December 1, 2005, and highlights the need for ongoing WNV surveillance, control of WNV mosquito vectors, and promotion by health departments of personal protection from mosquito bites, and research of additional prevention strategies.

Respiratory Syncytial Virus Activity –
United States, 2004 - 2005

Since the 2005-2006 annual seasonal activity of Respiratory Syncytial Virus (RSV) has begun, physicians should consider RSV in the differential diagnosis for persons of all ages with lower respiratory tract infection and should begin administering monthly prophylaxis to children who are at risk for serious RSV infection, including some premature infants or infants and children with chronic lung and heart disease.

Preliminary data reported to CDC’s National Respiratory and Enteric Virus Surveillance System (NREVSS) suggests the annual seasonal peak of Respiratory Syncytial Virus (RSV) has begun in the southern United States during the week ending October 15, 2005. This is slightly earlier than last year, where widespread RSV activity began the week ending November 13, 2004 and continued for 21 weeks, until April 2, 2005, with peak activity varying by region. During the annual winter seasonal peak, healthcare providers should consider RSV in the differential diagnosis for persons of all ages presenting with lower respiratory tract infection, implement appropriate isolation precautions to prevent spread of virus in hospitals, and provide monthly prophylaxis to children who are at risk for serious RSV infection, including some premature infants or infants and children with chronic lung and heart disease.

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