Editorial Note: The two outbreaks of gastroenteritis described above are representative of those frequently reported to CDC. They demonstrate the need for an improved, specific laboratory approach to identify the agents (many of which are presumed to be viral) responsible for these outbreaks (1,2). Transmission of these viruses is often associated with fecal contamination of water sources used for drinking, swimming, or producing ice (3). Additionally, the contamination of coastal water poses a special problem, since the consumption of seafood is a risk factor for acquiring Norwalk agent infection and other enteric viral agents. The two best-known enteric viral agents, rotavirus (group A) and Norwalk agent, were first seen in the stools of diarrhea patients by means of electron microscopy in the early 1970s. Both agents have proven to be important causes of gastroenteritis in this country, with rotavirus being the most common agent for diarrhea in young children (4) and Norwalk agent being common in adults (5). In recent years, enteric adenoviruses, non-group A rotavirus, and several 27- to 32-nm enteric viruses, including other Norwalk-like agents, caliciviruses, astroviruses, and other enteric viral pathogens, reportedly have been associated with gastroenteritis (1,6). Recent advances in identifying and diagnosing some of these viruses should make it possible to reduce the number of undiagnosed outbreaks in future investigations. Methods for serologic and antigenic tests are available for some agents, but the examination of stool samples by electron microscopy offers the possibility of identifying agents for which no specific tests are available. The probability of detecting viral particles by electron microscopy is greatest if stool specimens are collected during the early stages of illness, preferably within 12 hours and no later than 48 hours after onset. Some viral particles may be more stable if stool samples are stored at 4 °C. The following guidelines are currently recommended for specimen collection specifically for diagnosing outbreaks of viral gastroenteritis. 1. Stool specimens should be collected in bulk volume as soon after the time of disease onset as possible and no later than 48 hours after the onset of symptoms. 2. Stool specimens should be refrigerated, not frozen, and shipped to the laboratory on the same day that the specimen is collected. 3. Paired serum specimens that are collected within 1 week of the disease onset (acute phase) and 3 to 4 weeks after the onset of symptoms (convalescent phase) from both ill patients and controls are required to establish the causal association between agents seen in the stools and the illness. References 1. Dolin R, Treanor JJ, Madore HP. Novel agents of viral enteritis in humans. J Infect Dis 1987;155:365-76. 2. Ciba Foundation. Novel diarrhoea viruses. Chichester, United Kingdom: Wiley, 1987. (Symposium no. 128). 3. Centers for Disease Control. Outbreak of viral gastroenteritis-Pennsylvania and Delaware. MMWR 1987;36:709-11. 4. Brandt CD, Kim HW, Rodriguez WJ, et al. Pediatric viral gastroenteritis during eight years of study. J Clin Microbiol 1983;18:71-8. 5. Kapikian AZ, Chanock RM. Norwalk group of viruses. In: Fields BN, ed. Virology. New York: Raven Press, 1985:1495-517. 6. Cubitt WD, Blacklow NR, Herrmann JE, Nowak NA, Nakata S, Chiba S. Antigenic relationships between human caliciviruses and Norwalk virus. J Infect Dis 1987;156:806-14. Current Trends Recommendations for Protecting Human Health Against Potential Adverse Effects of Long-Term Exposure to In 1970, Congress gave the Department of Health and Human Services (DHHS) responsibility for reviewing Department of Defense (DOD) plans for transporting and/or disposing of certain chemical agents and making recommendations for the protection of human health and safety (Public Law [Pub. L.] 91-121/441 [50 USC 1512]). DHHS has delegated this authority to CDC. In 1985, Congress passed Pub. L. 99-145 (50 USC 1521), which mandates destruction of the present stockpile of selected chemical agents by September 30, 1994. The specific agents are listed below. In the absence of federal regulatory standards, DOD developed safety and health standards for handling these agents. In reviewing these standards and making its recommendations, CDC sought the assistance of a working group of experts. The national stockpile of chemical agents includes six chemicals: Nerve Agents GA (Tabun or ethyl N,N-dimethylphosphoramidocyanidate) GB (Sarin or isopropyl methylphosphonofluoridate) VX (S-[2-diisopropylaminoethyl] O-ethyl methyl phosphonothiolate) Vesicants/Blister Agents . H, HD (Sulfur mustard or di-2-chloroethyl sulfide) T (Bis(2-chloroethylthioethyl] ether) L (Lewisite or dichloro [2-chlorovinyl] arsine) Like a number of widely used insecticides, the nerve agents GA, GB, and VX are organic compounds containing phosphorus (organophosphorus compounds). They affect nerves, muscles, and glands by inhibiting acetyl cholinesterase, an enzyme required for proper function of these tissues. H and L (an organic compound containing arsenic) are vesicants. They cause chemical burns or blisters of the skin and mucous membranes, such as the conjunctiva of the eyes and the mucosa of airways. The bulk of the national stockpile consists of H, VX, and GB; therefore, CDC, through open meetings, convened a working group of experts to consider adverse effects of acute exposure to these agents. In 1987, DOD published an environmental impact statement that discussed options for destroying the national chemical stockpile. The preferred alternative was onsite incineration. DOD proposed building an incinerator at each of eight locations and burning the agent for complete chemical breakdown. The recommended control limits are based on air concentrations (Table 1). During public meetings held at each of the eight sites, citizens voiced their concerns about chronic low-level exposure to the agents and the delayed effects that acute exposure might cause. To resolve questions about these concerns, CDC gathered data on these agents and held an open meeting with the working group on September 29-30, 1987, in Atlanta, Georgia. The group discussed the potential health hazards that might result from the destruction of the stockpile, including organophosphate-induced delayed neuropathy, electroencephalographic (EEG) changes, cancer, birth defects, and keratitis. The group studied published and unpublished reports of all potential adverse effects, including carcinogenicity, mutagenicity, and teratogenicity, for the aforementioned agents. In addition, the U.S. Army Surgeon General's Office summarized a number of studies now under way or recently completed for agents GB, VX, HD, and L. Nerve degeneration is considered an unlikely outcome either from acute intoxication with any of the nerve agents or from long-term exposure to them. Given the difficulty of demonstrating EEG changes and the absence of clinically significant effects even if the EEG changes are present, members of the working group considered the EEG changes reported after intoxication with GB to be questionable. None of the nerve agents have been shown to be mutagenic or carcinogenic. Results of recently completed studies on GB and initial reports of studies on VX indicate no teratogenic effect. Available epidemiologic data indicate that H is a human carcinogen. Although the data suggest that H is less potent than such other known human carcinogens as smoking, radon, and chromates, they do not permit an estimate of the carcinogenic potency or the exact degree of the carcinogenic risk with confidence. Very little information is available on the long-term toxicity of agent T, which has much lower volatility than H, with which it is mixed. It is not expected to constitute an airborne hazard unless H is also present at concentrations much higher than permitted. Recommended control limits for agent T are therefore identical to those for H. Toxicologic information specific to L is sparse. More is known about arseniccontaining compounds in general, but caution must be used in extrapolation. Some evidence suggests that L might be a carcinogen. The recommended control concentration limit, 0.003 mg/m3 (measured as L), in air should be adequate to protect public health. The Occupational Safety and Health Administration (OSHA) has promulgated a standard of 0.5 mg/m3 (measured as arsenic) for organic arsenic concentrations in workplace air. The National Institute for Occupational Safety and Health (NIOSH) has recommended a standard of 0.002 mg/m3 for all forms of arsenic. The proposed L control limits are lower than the existing OSHA occupational standard for *Protection against exposure to agents in aerosol and liquid form must be sufficient to prevent direct contact with the skin and eyes. *GA = = Sarin or isopropyl Tabun or ethyl N,N-dimethylphosphoramidocyanidate; GB methylphosphonofluoridate; VX = S-(2-diisopropylaminoethyl) O-ethyl methyl phosphono thiolate. = $H or HD Sulfur mustard or di-2-chloroethyl sulfide; HT = Bis(2-chloroethylthioethyl) ether (T) in a mixture with sulfur mustard; L Lewisite or dichloro (2-chlorovinyl) arsine. "Data supporting the ability to monitor for H at 0.0001 mg/m3 at all sites should be developed. HT is measured as HD. Exposure - Continued organic arsenic by a factor of approximately 500 and are lower than the NIOSH recommended standard by a factor of 2. Reported by: Special Programs Group, Office of the Director, Center for Environmental Health and Injury Control, Centers for Disease Control. Editorial Note: CDC, in its continuous oversight of demilitarization activity, routinely examines each of the eight chemical storage sites in the United States and a chemical munitions incineration facility that has been in operation in Utah since 1979. Consideration is given to the population centers in the surrounding communities at depots. Standard operating procedures for agent handling and worker safety are also observed. This experience indicates that the control limits in Table 1 are attainable. Questions related to the nerve agents have been relatively easy to resolve. The information bases are fairly complete, and there appears to be little risk either of adverse health effects from long-term exposure to low doses or of delayed health effects from acute exposure. Anthrax TABLE II. Notifiable diseases of low frequency, United States Diphtheria *Two of the 22 reported cases for this week were imported from a foreign country or can be directly traceable to a known internationally imported case within two generations. |