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Dengue -- Mexico, El Salvador, Honduras

During the past 4 months, increased dengue activity has been reported in Mexico, El Salvador, and Honduras.

Mexico: In late June and early July 1983, increased numbers of cases of dengue-like illness were reported from Puebla in the state of Puebla, Mexico. In subsequent weeks, outbreaks of dengue-like illness became widespread, with reports on the Pacific coast from Chiapas in the south to Jalisco in the north. In addition, cases were reported from Veracruz and Yucatan on the east coast of the country.

Through week 32, 3,527 cases were reported to Mexican health authorities. The largest numbers were reported from the states of Oaxaca (759), Guerrero (725), and Michoacan (542) on the Pacific coast and Yucatan (592) and Veracruz (286) on the east coast. Additional cases have been reported from Chiapas, Puebla, Morelos, and Jalisco. Several of the outbreaks have occurred in cities that had not previously reported dengue. The reports indicate that dengue transmission is widespread in Mexico.

Clinically, the illness has presented as classical dengue. According to Mexican health authorities, a few cases of severe disease reported in some parts of the Isthmus of Tehuantepec, Oaxaca, were not confirmed as dengue.

The serotypes responsible for all the outbreaks are not known, but serologic and virologic data from the Institute of Public Health and Tropical Diseases in Mexico City have shown that dengue 1 is responsible for some. Thus, three dengue 1 viruses were isolated from patients in Puebla, with onsets in July. The identification of these isolates was confirmed by CDC. Three additional virus isolations have been made--two from Puebla and one from Tapachula, Chiapas; identification is pending. Serologic conversions to dengue have been confirmed in 30.5% of cases tested by the laboratory in Mexico City.

El Salvador: In late June and early July, increased numbers of cases of dengue-like illness were reported in San Salvador, El Salvador. The illness was generally mild and of the classical type. No hemorrhagic manifestations were reported.

Ministry of Health officials collected blood samples from 14 patients who had onset in late June or the first week of July. Convalescent samples were subsequently collected from 10 of these patients and sent to CDC for testing. Of the 10 paired sera, seven showed a fourfold or greater rise in hemagglutination inhibition (HI) and complement fixation (CF) antibodies to dengue between acute- and convalescent-phase samples. Five of the seven patients had primary serologic responses, which were monotypic for dengue 4. The others, as well as a patient with a single, late acute sample, had secondary serologic responses. Dengue 4 virus has been isolated from the acute sera of two patients, one with a primary dengue infection, the other with a serologically confirmed secondary dengue infection.

Through August, 2,867 dengue cases were reported in El Salvador, with the majority reported in July and August; numbers are not available for September. The cases were reported from all areas of the country, with most (1,005) reported from the eastern region bordering Honduras. Although laboratory data are limited, seven of the 10 patients with paired sera from San Salvador were positive for dengue. Such a high rate of case confirmation is usually only observed during periods of epidemic transmission.

Honduras: Dengue 1 has recently been confirmed serologically in Honduras by the Department of Microbiology, Universidad Nacional Autonoma de Honduras. No information is available as to the patient's residence or date of onset. Reports suggest, however, that dengue-like illnesses have increased in San Pedro Sula since July, but no specimens or information on numbers of cases are available. Reported by L Cabrera-Coello, MD, Subdirector de Vigilancia y Epidemiologia, Secretaria de Salubridad y Asistencia, Mexico City, E Zorilla, MD, Director, ML Zarate de Guaneros, MD, Head, Virology Dept, Instituto de Salubridad y Enfermedades Tropicales, Mexico City, Mexico; R Hernandez, MD, Chief, JL Guzman, MD, Assistant Chief, Div of Epidemiology, Ministry of Health, A Lago, MD, Epidemiologist, OPS/OMS, El Salvador; M Figueroa, MD, Dept of Microbiology, Universidad Nacional Autonoma de Honduras, Honduras; Dengue Br, Div of Vector-Borne Viral Diseases, Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: These reports indicate that both dengue 1 and 4 are still active in Mexico and Central America. Additionally, serologic and virologic data suggest that dengue 2 is also being transmitted in the region.

Both Mexico and El Salvador experienced dengue epidemics in the summer of 1982. In Mexico, available evidence suggested most activity was then due to dengue 1, as it is now. This is supported by the fact that the 1983 epidemics are in different cities and states than those reported in 1982. The virus serotype responsible for the 1982 epidemic in El Salvador was not confirmed virologically, but serologic evidence of dengue 4 was obtained from an American traveler to the country at that time. The 1983 epidemic in San Salvador appears due to this serotype as well.

Although detailed information is not available from Honduras, the fact that most reported cases from El Salvador have been from the eastern region bordering Honduras and that there has been increased activity reported in San Pedro Sula suggests widespread activity in that country as well. Health authorities in Guatemala have not reported increased dengue activity in that country.

Persons traveling to these countries should be made aware of possible dengue infection and should take routine precautions against mosquitoes.

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