Hurricane Katrina struck the U.S. Gulf Coast on August 29, 2005, resulting in extensive structural damage and severe flooding from breached levees in and around New Orleans. In the four weeks after the hurricane made landfall, a total of 7,508 illnesses and injuries were reported, according to the Centers for Disease Control and Prevention (CDC). Reports on illnesses in hurricane evacuees and relief workers were published in the September 23, September 30, October 7, and October 14, 2005, issues of Morbidity and Mortality Weekly Report (http://www.cdc.gov/mmwr).

Of the 6,167 illnesses and injuries in which disposition status was known, five persons died and 552 (9.0 percent) were admitted to hospitals. Among those injured, 42 had intentional injuries (i.e., self-inflicted or violent), seven of whom were victims of assault. The proportion of ill patients evaluated for acute respiratory infection (ARI) increased from September 8 to September 25, when data were analyzed. Among the 505 patients with ARI, 371 (73.5 percent) had cough, 62 (12.3 percent) had shortness of breath, and 60 (11.9 percent) had fever. A total of 23 persons with ARI (4.6 percent) were admitted to a hospital.

Rash illnesses also increased over time. Relief workers were significantly more likely than residents to be seen for a rash (odds ratio [OR], 1.7). These rashes were noninfectious; they were classified as prickly heat, arthropod bites, and the abrasive effects of wet clothing and moist skin. Motor vehicle crashes were responsible for 145 of the 2,018 injuries (7.2 percent); motor vehicle crashes accounted for a smaller proportion of injuries among relief workers (5.0 percent) than among residents (9.2 percent; OR, 0.55). As of September 25, 14 cases of carbon monoxide poisoning had been detected, and 27 persons were exposed to other toxic substances (e.g., diesel fuel, contaminated water, cleaning agents).

NOROVIRUS OUTBREAK IN EVACUEES

During the week after Hurricane Katrina made landfall, an estimated 240,000 persons, mostly from Louisiana, evacuated to Houston. On August 31, an estimated 24,000 evacuees were sheltered temporarily at facilities in Reliant Park, a sports and convention complex. On September 2, physicians and public health workers noted a substantial number of adults and children with symptoms of acute gastroenteritis at the medical clinic in Reliant Park.

Approximately 6,500 of the estimated 24,000 evacuees visited the Reliant Park medical clinic between September 2 and September 12, and 1,169 persons (18 percent) reported symptoms of acute gastroenteritis. The number of persons with acute gastroenteritis peaked on September 5, when 211 persons reported symptoms, and cases declined slowly thereafter. A total of 511 patients (44 percent) with acute gastroenteritis symptoms had diarrhea only, 342 (29 percent) reported vomiting only, and 316 (27 percent) reported diarrhea and vomiting. In addition, health care professionals, police officers, and volunteers who had direct contact with patients reported acute gastroenteritis symptoms, suggesting substantial secondary spread, presumably by person-to-person contact or fomite transmission. The number of hospitalizations was unknown; no deaths were reported.

Stool samples (i.e., rectal swabs or bulk stools) were collected for laboratory diagnosis of bacterial, parasitic, and viral enteropathogens. Norovirus was confirmed in one half of stool samples from 44 patients tested by reverse transcription-polymerase chain reaction; no other enteropathogen was identified.

At the beginning of the outbreak, health care professionals implemented extensive infection-control measures. Patients with acute gastroenteritis and dehydration were rehydrated in a separate observation area reserved for patients with suspected infectious illness and then transferred to an isolation area for at least 48 hours after vomiting and diarrhea ended. In addition, alcohol-based gel hand sanitizers were distributed throughout the facilities and near lavatories, and a bank of portable sinks was installed inside the medical clinic. Medical staff, disaster relief workers, volunteers, and evacuees were alerted to the heightened need for proper handwashing techniques. Despite these timely interventions, the outbreak continued for more than one week but declined before the evacuees vacated Reliant Park in late September 2005.

VIBRIO ILLNESSES AFTER HURRICANE KATRINA

In the two weeks after Hurricane Katrina made landfall, 22 new cases of Vibrio illness were identified and five Vibrio-related deaths were reported. These illnesses were caused by Vibrio vulnificus, Vibrio parahaemolyticus, and non-toxigenic Vibrio cholerae. These organisms are unlikely to cause outbreaks from person-to-person transmission. No cases of toxigenic V. cholerae serogroups O1 or O139, the causative agents of cholera, were identified. These illnesses underscore the need for heightened clinical awareness, appropriate culturing of specimens from patients, and empiric treatment of illnesses (particularly those associated with wound infections) caused by Vibrio species.

Eighteen wound-associated Vibrio cases were reported in residents of Mississippi and Louisiana; in persons displaced from Louisiana to Texas, Arkansas, and Arizona; and in one person displaced from Mississippi to Florida.

Speciation was performed in clinical laboratories for 17 of the wound-associated cases; 14 were V. vulnificus, and three were V. parahaemolyticus. Five patients with wound-associated Vibrio infections died; three deaths were associated with V. vulnificus infection, and two were associated with V. parahaemolyticus infection.

An underlying condition that may have increased the risk for severe Vibrio illness was reported in 13 (72 percent) of the patients with wounds; these conditions included heart disease, diabetes mellitus, renal disease, alcoholism, liver disease, peptic ulcer disease, immunodeficiency, and malignancy.

Four persons were reported with non–wound-associated Vibrio infections (two in Mississippi, one in Louisiana, and one displaced from Louisiana to Arizona). Information on the Vibrio species and clinical illness was available for two of these patients; the species were nontoxigenic V. cholerae isolated from patients with gastroenteritis. No deaths were reported in patients with non-wound infections.

After natural disasters such as Hurricane Katrina, the risk for illness related to infectious diseases is a public health concern. The CDC findings underscore the need for prompt recognition and management of Vibrio wound infections by health care professionals.

V. vulnificus wound infections can begin as redness and swelling at the site of the wound and rapidly progress in patients at high risk to cause systemic illness, including sepsis. V. vulnificus typically causes a severe and life-threatening illness characterized by fever and chills, decreased blood pressure (septic shock), and blood-tinged blistering skin lesions (hemorrhagic bullae). Persons with chronic liver disease or immunocompromising conditions are particularly at risk for severe V. vulnificus infections.

V. parahaemolyticus typically causes gastroenteritis after consumption of contaminated shellfish. Less commonly, V. parahaemolyticus causes wound infections that are generally less severe than V. vulnificus wound infections. However, in persons with liver disease or immunocompromising conditions, V. parahaemolyticus wound infections can cause death.

Nontoxigenic V. cholerae primarily causes gastroenteritis, but unlike toxigenic V. cholerae O1 or O139, nontoxigenic V. cholerae does not cause epidemics. Illness caused by this organism ranges in severity from mild diarrhea to severe watery diarrhea. Fever and bloody diarrhea typically are not observed. Immunocompromised persons and persons with liver disease can experience a more severe illness, including fever, chills, and septic shock. This organism rarely has been reported to cause wound infections.

Vibrio infections are diagnosed by culture of wound, blood, or stool specimens. For stool specimens, a selective media of thiosulfate-citrate-bile salts-sucrose agar (TCBS) is recommended. If there is clinical suspicion of enteric Vibrio infection, the laboratory should be notified so that TCBS media will be used.

Persons working in hurricane-damaged areas, especially in areas with standing brackish water, should wear boots and other protective gear to prevent wounds and to prevent exposure of broken skin to contaminated water. To prevent Vibrio infections, persons with open wounds or broken skin should avoid contact with brackish water or seawater, especially if they have preexisting liver disease or other immunocompromising conditions. Injury prevention is especially important in these high-risk populations. Healthy persons are at much lower risk for Vibrio infection. In areas where floodwaters have receded and surfaces are dry, Vibrio should not be a concern because the organism is killed rapidly by drying.

To reduce the risk for Vibrio wound infection, persons should wash all wounds that have been exposed to sea or brackish waters with soap and clean water as soon as possible and seek medical care for any wound that appears infected. Physicians should be vigilant for Vibrio infection in hurricane evacuees, particularly in patients with infected wounds and especially if the patients are in a high-risk group. If V. vulnificus infection is suspected, anti-microbial therapy should be started immediately; prompt treatment can improve survival. Antimicrobials effective against Vibrio infections include doxycycline (Vibramycin), third-generation cephalosporins (e.g., ceftazidime [Fortaz]), fluoroquinolones, and aminoglycosides. Wound infections also should be treated with aggressive attention to the wound site; amputation of the infected limb is sometimes necessary. For Vibrio gastroenteritis that is mild and self-limited, treatment with oral rehydration usually is sufficient. Antimicrobial therapy might be helpful for patients with severe or prolonged diarrhea.