Water crisis in Cape Town is already posing a risk to public health.

The water crisis hitting Cape Town is increasing the danger of diseases that surge when people do not wash their hands.

The four million residents of South Africa’s second-largest city are being urged to get by on 50 liters (13 gallons) of water per person per day. That leaves roughly 2 liters (0.5 gallons) a day for washing hands and brushing teeth, or roughly one-eighth the amount of water than most people consume each time they wash their hands and face.

The restrictions have spurred officials to warn about potential risks to public health. “We are talking fecal-oral contamination of the water, the food and the hands... in the health facilities, we are all on alert,” Virginia De Azevedo, health manager for the city’s Khayelitsha township, said at a briefing on Monday. Sanitizing gels do not substitute for washing hands with potable water, she added.

Together, we can avoid #DayZero. Here's how you can get by on 50 litres of water per person

per day. #SaveWaterpic.twitter.com/5g6hs26Yk0

— Western Cape Gov (@WesternCapeGov) February 2, 2018

The warnings come amid a seasonal spike in diarrhea that occurs annually in Cape Town from February through April, when warmer weather encourages the spread of germs.

The Western Cape province also is battling the second-highest incidence of listeriosis in South Africa, which is suffering from the largest outbreak of the disease on record. At least 820 people have been infected and 82 have died since the start of last year, according to data from the National Institute for Communicable Diseases.

Listeriosis, which particularly threatens newborns, can spread through inadequate hand-washing and a failure to rinse fruits, vegetables and other raw foods thoroughly. Officials warn that such water-borne borne illnesses as cholera, hepatitis A and typhoid fever “likely will become more prevalent” as locals take to storing water in contaminated containers.

In recent years, residents of Flint, Michigan, Rio de Janeiro, India and Haiti all have confronted outbreaks of illnesses that surge whenever communities suffer from shortages of clean water.

If the drought in Cape Town persists into South Africa’s winter months (June to August), the city also could see “increased transmission” of respiratory viruses and other infections “that can be transmitted by skin contact,” says Marc Mendelson, a professor of medicine and head of infectious diseases at the University of Cape Town.

Such projections remain conjecture, he adds, as the city has yet to experience an uptick in diarrhea among infants compared with prior years.

Amid the clampdown, residents of Cape Town have begun to reuse water left over from washing dishes, as well as turned to water drawn from springs, wells, boreholes and rainwater tanks.

Though residents can use such sources to flush toilets or to clean clothes and work surfaces, local officials caution that only water from municipal taps or bottled water is safe to drink.

“While there are many dos and don’ts for the use of alternative water sources, there is one common thread and that is that it should not be used for drinking or cooking and in most cases not for personal hygiene either,” said JP Smith, an alderman who sits on the mayor’s committee for safety and security.