No new deaths were recorded, with the fatality toll remaining on 36.
The Disease Prevention and Control Center (SPKC) said 2,264 tests had been conducted during the previous 24-hour period.
In total 290,907 tests have been carried out since February 29.
So far 1,248 patients have recovered from infection.
Seven patients are in hospital, all of whom are described as having moderate symptoms of the disease.
Pēdējās 24h veikti 2264 COVID-19 testi, reģistrēti 4 jauni saslimšanas gadījumi. Latvijā kopā veikti 290 907 izmeklējumi, saslimušas 1498 personas un 1248 izveseļojušās, 36 mirušas.
— SPKC.gov.lv (@SPKCentrs) September 18, 2020
SPKC added that three of the new patients had been in contact with an infected person, one is still being investigated.
On September 17 the 14-day cumulative number of COVID-19 cases per 100,000 of population was 4.2 in Latvia, 17.3 in Lithuania and 25.4 in Estonia.
The threshold for the introduction of compulsory self-isolation upon arrival in Latvia is 16. See our other story about the latest list of countries which require self-isolation for people arriving in Latvia. The country list is to be updated today.
COVID-19 information
A useful summary in English of the latest COVID-19 situation including restrictions in place and rules on public assembly is available at this special government website.
Cīņa ar #COVID19 izplatību nav noslēgusies - iepazīsties ar noteikumiem, kurus nepieciešams ievērot savas un sabiedrības veselības saglabāšanas nolūkā arī pēc ārkārtējās situācijas noslēguma! ☝?
— Valdības māja (@Brivibas36) June 10, 2020
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The number for medical emergencies is 113, the number for enquiring about a COVID-19 test if you have developed some potential symptoms after returning from overseas or being in contact with someone confirmed as having coronavirus is 8303 and the SPKC COVID-19 advice helpline is 67387661.
The SPKC has information in English about the approved methods of protecting yourself from the virus, symptoms and medical procedures and an interactive map plotting the incidence and distribution of the disease in Latvia.