A s the coronavirus disease (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) unfolds, an increasing number of reports have indicated that some infected persons may not exhibit signs or symptoms of illness, including persons who are presymptomatic (SARS-CoV-2 RNA is detectable before symptom onset) or asymptomatic (SARS-CoV-2 RNA is detectable but symptoms never develop) (1-8). The detection of SARS-CoV-2 RNA in presymptomatic or asymptomatic persons does not prove that they can transmit the virus to others. We describe evidence that supports the concept of transmission while presymptomatic and asymptomatic, which we found during a rapid literature review conducted at the Centers for Disease Control and Prevention (CDC) in early April 2020. Evidence Supporting Presymptomatic and Asymptomatic Transmission We searched the literature in PubMed for articles that were published from January 1 through April 2, 2020, and pertained to presymptomatic or asymptomatic SARS-CoV-2 transmission. This search captured the literature until the time CDC made policy changes recommending community cloth face coverings and universal masking in healthcare facilities. We used combinations of the search terms SARS-CoV-2, COV-ID-19, asymptomatic, presymptomatic, and transmission. We included original articles, brief reports, and correspondences and excluded reviews, commentaries, opinions, and preprint manuscripts (with the exception of CDC-authored studies that were in review). We classified studies as reporting epidemiologic, virologic, or modeling evidence for presymptomatic or asymptomatic transmission of SARS-CoV-2. Epidemiologic Evidence Most reports of presymptomatic (9-12), asymptomatic (13-15), or a combination of presymptomatic or asymptomatic SARS-CoV-2 transmission (16,17) were from China (Table 1). Presymptomatic or asymptomatic primary patients were typically exposed to SARS-CoV-2 during travel from Wuhan or another city in Hubei Province, China (9-16). One couple was exposed during a mass gathering in Shanghai for the Chinese Spring Festival (17). Reported cases of infected persons who transmitted the virus to others while presymptomatic or asymptomatic have occurred within families or households (9-11,13-17), during shared meals (10,12), or during visits with hospitalized family members (9,13). An inherent confounder to these reports from China is the inability to entirely rule out alternative SARS-CoV-2 exposure in the community early in the

Botulism is a rare disease with 4 naturally occurring syndromes: foodborne botulism is caused by ingestion of foods contaminated with botulinum toxin, wound botulism is caused by Clostridium botulinum colonization of a wound and in situ toxin production, infant botulism is caused by intestinal colonization and toxin production, and adult intestinal toxemia botulism is an even rarer form of intestinal colonization and toxin production in adults. Inhalational botulism could result from aerosolization of botulinum toxin, and iatrogenic botulism can result from injection of toxin. All forms of botulism produce the same distinct clinical syndrome of symmetrical cranial nerve palsies followed by descending, symmetric flaccid paralysis of voluntary muscles, which may progress to respiratory compromise and death. The mainstays of therapy are meticulous intensive care (including mechanical ventilation, when necessary) and timely treatment with antitoxin.

L. monocytogenes is a cause of gastroenteritis with fever, and sporadic cases of invasive listeriosis may be due to unrecognized outbreaks caused by contaminated food.

In 2006, a total of 178 cases of acute Chagas disease were reported from the Amazonian state of Pará, Brazil. Eleven occurred in Barcarena and were confirmed by visualization of parasites on blood smears. Using cohort and case–control studies, we implicated oral transmission by consumption of açaí palm fruit.